Staff directory Laura Lechuga Gómez

Laura Lechuga Gómez

CSIC Research Professor and Group Leader
NanoBiosensors and Bioanalytical Applications



  • Biomimetic nanoplasmonic sensor for rapid evaluation of neutralizing SARS-CoV-2 monoclonal antibodies as antiviral therapy

    Batool, R; Soler, M; Colavita, F; Fabeni, L; Matusali, G; Lechuga, LM Biosensors & Bioelectronics; 226: 115137. 2023. 10.1016/j.bios.2023.115137. IF: 12.600

  • Integration of Metal-Organic Polyhedra onto a Nanophotonic Sensor for Real-Time Detection of Nitrogenous Organic Pollutants in Water

    Calvo-Lozano, O; Hernandez-Lopez, L; Gomez, L; Carne-Sanchez, A; von Baeckmann, C; Lechuga, LM; Maspoch, D ACS APPLIED MATERIALS & INTERFACES; 2023. 10.1021/acsami.3c07213. IF: 9.500

  • Using Electrochemical Immunoassay in a Novel Microtiter Plate to Detect Surface Markers of Preeclampsia on Urinary Extracellular Vesicles

    Lee, S; Gonzalez-Suarez, AM; Huang, XH; Calvo-Lozano, O; Suvakov, S; Lechuga, LM; Garovic, VD; Stybayeva, G; Revzin, A Acs Sensors; 8 (1): 207 - 217. 2023. 10.1021/acssensors.2c02077. IF: 8.900


  • Biochemistry strategies for label-free optical sensor biofunctionalization: advances towards real applicability

    Soler M., Lechuga L.M. Analytical and Bioanalytical Chemistry; 414 (18): 5071 - 5085. 2022. 10.1007/s00216-021-03751-4. IF: 4.157

    Label-free biosensors, and especially those based on optical transducers like plasmonic or silicon photonic systems, have positioned themselves as potential alternatives for rapid and highly sensitive clinical diagnostics, on-site environmental monitoring, and for quality control in foods or other industrial applications, among others. However, most of the biosensor technology has not yet been transferred and implemented in commercial products. Among the several causes behind that, a major challenge is the lack of standardized protocols for sensor biofunctionalization. In this review, we summarize the most common methodologies for sensor surface chemical modification and bioreceptor immobilization, discussing their advantages and limitations in terms of analytical sensitivity and selectivity, reproducibility, and versatility. Special focus is placed on the suggestions of innovative strategies towards antifouling and biomimetic functional coatings to boost the applicability and reliability of optical biosensors in clinics and biomedicine. Finally, a brief overview of research directions in the area of device integration, automation, and multiplexing will give a glimpse of the future perspectives for label-free optical biosensors. © 2021, The Author(s).

  • Coating Bioactive Microcapsules with Tannic Acid Enhances the Phenotype of the Encapsulated Pluripotent Stem Cells

    Choi D., Gwon K., Hong H.J., Baskaran H., Calvo-Lozano O., Gonzalez-Suarez A.M., Park K., De Hoyos-Vega J.M., Lechuga L.M., Hong J., Stybayeva G., Revzin A. ACS Applied Materials and Interfaces; 14 (23): 27274 - 27286. 2022. 10.1021/acsami.2c06783.

    Human pluripotent stem cells (hPSCs) may be differentiated into any adult cell type and therefore hold incredible promise for cell therapeutics and disease modeling. There is increasing interest in three-dimensional (3D) hPSC culture because of improved differentiation outcomes and potential for scale up. Our team has recently described bioactive heparin (Hep)-containing core-shell microcapsules that promote rapid aggregation of stem cells into spheroids and may also be loaded with growth factors for the local and sustained delivery to the encapsulated cells. In this study, we explored the possibility of further modulating bioactivity of microcapsules through the use of an ultrathin coating composed of tannic acid (TA). Deposition of the TA film onto model substrates functionalized with Hep and poly(ethylene glycol) was characterized by ellipsometry and atomic force microscopy. Furthermore, the presence of the TA coating was observed to increase the amount of basic fibroblast growth factor (bFGF) incorporation by up to twofold and to extend its release from 5 to 7 days. Most significantly, TA-microcapsules loaded with bFGF induced higher levels of pluripotency expression compared to uncoated microcapsules containing bFGF. Engineered microcapsules described here represent a new stem cell culture approach that enables 3D cultivation and relies on local delivery of inductive cues. © 2022 American Chemical Society. All rights reserved.

  • Integrated optical bimodal waveguide biosensors: Principles and applications

    Torrijos-Morán L., Lisboa B.D., Soler M., Lechuga L.M., García-Rupérez J. Results in Optics; 9 (100285) 2022. 10.1016/

    Integrated optical biosensors have become one of the most compelling technologies for the achievement of highly sensitive, multianalyte, portable and easy to use point-of-care (POC) devices with tremendous impact in healthcare and environmental protection, among other application fields. In this context, bimodal waveguide (BiMW) interferometers have emerged over the last years as a powerful biosensor technology providing the benefits of extreme sensitivity under a label-free scheme, reliability and robustness within a highly compact footprint that can be integrated and multiplexed in lab-on-a-chip (LOC) platforms. In this review, we provide an overview of the state-of-the-art about integrated optical BiMW biosensors from the theoretical fundamentals to their practical implementation. Furthermore, we explore recent advances such as novel designs, integration in specific LOC systems and its application in real biosensing scenarios. Final remarks and perspectives on the potential impact of these biosensor interferometric structures are also provided, as well as some limitations that must be addressed in next steps. © 2022 The Author(s)

  • Label-Free Plasmonic Biosensor for Rapid, Quantitative, and Highly Sensitive COVID-19 Serology: Implementation and Clinical Validation

    Calvo-Lozano O., Sierra M., Soler M., Estévez M.C., Chiscano-Camón L., Ruiz-Sanmartin A., Ruiz-Rodriguez J.C., Ferrer R., González-López J.J., Esperalba J., Fernández-Naval C., Bueno L., López-Aladid R., Torres A., Fernández-Barat L., Attoumani S., Charrel R., Coutard B., Lechuga L.M. Analytical Chemistry; 94 (2): 975 - 984. 2022. 10.1021/acs.analchem.1c03850. IF: 6.986

    Serological tests are essential for the control and management of COVID-19 pandemic (diagnostics and surveillance, and epidemiological and immunity studies). We introduce a direct serological biosensor assay employing proprietary technology based on plasmonics, which offers rapid (<15 min) identification and quantification of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies in clinical samples, without signal amplification. The portable plasmonic device employs a custom-designed multiantigen (RBD peptide and N protein) sensor biochip and reaches detection limits in the low ng mL–1 range employing polyclonal antibodies. It has also been implemented employing the WHO-approved anti-SARS-CoV-2 immunoglobulin standard. A clinical validation with COVID-19 positive and negative samples (n = 120) demonstrates its excellent diagnostic sensitivity (99%) and specificity (100%). This positions our biosensor as an accurate and easy-to-use diagnostics tool for rapid and reliable COVID-19 serology to be employed both at laboratory and decentralized settings for the disease management and for the evaluation of immunological status during vaccination or treatment. © 2021 The Authors. Published by American Chemical Society

  • Novel Sensing Algorithm for Linear Read-Out of Bimodal Waveguide Interferometric Biosensors

    Bassols-Cornudella B., Ramirez-Priego P., Soler M., Estevez M.-C., Luis-Ravelo H.J.D., Cardenosa-Rubio M., Lechuga L.M. Journal of Lightwave Technology; 40 (1): 237 - 244. 2022. 10.1109/JLT.2021.3118103. IF: 4.142

    Biosensors employing photonics integrated circuits, and specifically those that rely on interferometric evanescent wave working principles, have outstanding performances due to the extreme sensitivity exhibited in one-step and direct assay, without the need of amplification. Within the interferometric configurations, the Bimodal Waveguide (BiMW) interferometric sensor stands out due to its demonstrated sensitivity for real-life applications and the simplicity of its design. To overcome the ambiguities that arise from the periodic nature of interferometric read-outs, a new all-optical modulation and the subsequent trigonometry-based algorithm have been proposed and applied to the BiMW biosensor. This new algorithm has been successfully employed for the selective identification and quantification of the external Spike (S) protein of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Our biosensing results from this simple, quick, and user-friendly method demonstrate high sensitivity and specificity and pave the way towards a point-of-care device for general use. © 1983-2012 IEEE.

  • One-Step and Real-Time Detection of microRNA-21 i n Human Samples for Lung Cancer Biosensing Diagnosis

    Calvo-Lozano, O; Garcia-Aparicio, P; Raduly, LZ; Estevez, MC; Berindan-Neagoe, I; Ferracin, M; Lechuga, LM Analytical Chemistry; 94 (42): 14659 - 14665. 2022. 10.1021/acs.analchem.2c02895. IF: 8.008

  • Rapid and direct quantification of the SARS-CoV-2 virus with an ultrasensitive nanobody-based photonic nanosensor

    Ruiz-Vega, Gisela; Soler, Maria; Estevez, MCarmen; Ramirez-Priego, Patricia; Pazos, Martalu D.; Noriega, María A.; Margolles, Yago; Francés-Gómez, Clara; Geller, Ron; Matusali, Giulia; Colavita, Francesca; di Caro, Antonino; Casasnovas, José M.; Fernández, Luis Angel; Lechuga, Laura M. Sensors &Amp; Diagnostics; 2022. 10.1039/d2sd00082b.


  • COVID-19 biosensing technologies

    Merkoçi A., Li C.-Z., Lechuga L.M., Ozcan A. Biosensors and Bioelectronics; 178 (113046) 2021. 10.1016/j.bios.2021.113046. IF: 10.618

  • Current trends in spr biosensing of sars-cov-2 entry inhibitors

    Mauriz E., Lechuga L.M. Chemosensors; 9 (12, 330) 2021. 10.3390/chemosensors9120330. IF: 3.398

    The emerging risk of viral diseases has triggered the search for preventive and therapeutic agents. Since the beginning of the COVID-19 pandemic, greater efforts have been devoted to investigating virus entry mechanisms into host cells. The feasibility of plasmonic sensing technologies for screening interactions of small molecules in real time, while providing the pharmacokinetic drug profiling of potential antiviral compounds, offers an advantageous approach over other biophysical methods. This review summarizes recent advancements in the drug discovery process of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) inhibitors using Surface Plasmon Resonance (SPR) biosensors. A variety of SPR assay formats are discussed according to the binding kinetics and drug efficacies of both natural products and repurposed drugs. Special attention has been given to the targeting of antiviral agents that block the receptor binding domain of the spike protein (RBD-S) and the main protease (3CLpro) of SARS-CoV-2. The functionality of plasmonic biosensors for high-throughput screening of entry virus inhibitors was also reviewed taking into account experimental parameters (binding affinities, selectivity, stability), potential limitations and future applications. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

  • Design and characterization of high-affinity synthetic peptides as bioreceptors for diagnosis of cutaneous leishmaniasis

    Prada Y.A., Soler M., Guzmán F., Castillo J.J., Lechuga L.M., Mejía-Ospino E. Analytical and Bioanalytical Chemistry; 413 (17): 4545 - 4555. 2021. 10.1007/s00216-021-03424-2. IF: 4.157

    Cutaneous leishmaniasis (CL) is one of the illnesses caused by Leishmania parasite infection, which can be asymptomatic or severe according to the infecting Leishmania strain. CL is commonly diagnosed by directly detecting the parasites or their DNA in tissue samples. New diagnostic methodologies target specific proteins (biomarkers) secreted by the parasite during the infection process. However, specific bioreceptors for the in vivo or in vitro detection of these novel biomarkers are rather limited in terms of sensitivity and specificity. For this reason, we here introduce three novel peptides as bioreceptors for the highly sensitive and selective identification of acid phosphatase (sAP) and proteophosphoglycan (PPG), which have a crucial role in leishmaniasis infection. These high-affinity peptides have been designed from the conservative domains of the lectin family, holding the ability to interact with the biological target and produce the same effect than the original protein. The synthetic peptides have been characterized and the affinity and kinetic constants for their interaction with the targets (sAP and PPG) have been determined by a surface plasmon resonance biosensor. Values obtained for KD are in the nanomolar range, which is comparable to high-affinity antibodies, with the additional advantage of a high biochemical stability and simpler production. Pep2854 exhibited a high affinity for sAP (KD = 1.48 nM) while Pep2856 had a good affinity for PPG (KD 1.76 nM). This study evidences that these peptidomimetics represent a novel alternative tool to the use of high molecular weight proteins for biorecognition in the diagnostic test and biosensor devices for CL. Graphical abstract: [Figure not available: see fulltext.]. © 2021, Springer-Verlag GmbH Germany, part of Springer Nature.

  • Nanophotonic biosensors for point-of-care COVID-19 diagnostics and coronavirus surveillance

    Ruiz-Vega G., Soler M., Lechuga L.M. JPhys Photonics; 3 (1, 011002) 2021. 10.1088/2515-7647/abd4ee. IF: 0.000

    The COVID-19 pandemic has revealed the need of novel diagnostic technologies for rapid and accurate virus detection. In the European CONVAT project, a point-of-care nanophotonic biosensor is being developed for the direct, fast and specific identification of severe acute respiratory syndrome coronavirus 2 from both human patient samples and animal reservoirs. The technology will provide a quantitative detection of the viral load and it can be implemented in decentralized settings to improve the early diagnosis and clinical management of patients as well as coronavirus environmental monitoring to prevent future outbreaks. © 2021 The Author(s). Published by IOP Publishing Ltd

  • Plasmonic biosensors for single-molecule biomedical analysis

    Mauriz E., Lechuga L.M. Biosensors; 11 (4, 123) 2021. 10.3390/bios11040123. IF: 5.519

    The rapid spread of epidemic diseases (i.e., coronavirus disease 2019 (COVID-19)) has contributed to focus global attention on the diagnosis of medical conditions by ultrasensitive detection methods. To overcome this challenge, increasing efforts have been driven towards the development of single-molecule analytical platforms. In this context, recent progress in plasmonic biosensing has enabled the design of novel detection strategies capable of targeting individual molecules while evaluating their binding affinity and biological interactions. This review compiles the latest advances in plasmonic technologies for monitoring clinically relevant biomarkers at the single-molecule level. Functional applications are discussed according to plasmonic sensing modes based on either nanoapertures or nanoparticle approaches. A special focus was devoted to new analytical developments involving a wide variety of analytes (e.g., proteins, living cells, nucleic acids and viruses). The utility of plasmonic-based single-molecule analysis for personalized medicine, considering technological limitations and future prospects, is also overviewed. © 2021 by the authors.

  • Principles, technologies, and applications of plasmonic biosensors

    Soler M., Lechuga L.M. Journal of Applied Physics; 129 (11, 111102) 2021. 10.1063/5.0042811. IF: 2.546

    Plasmonic materials and phenomena have been widely studied and applied in multiple fields for a long time. One of the most promising applications is in the engineering of biosensor devices, offering label-free and real-time analysis of biomolecular interactions with excellent performances. In this tutorial, we provide a pedagogical review of the working principles of plasmonic biosensors, main fabrication methods, instrumentation, and general guidelines for their development. Special focus is placed on the biosensor performance characterization and assessment, as well as on the sensor surface biofunctionalization. In the end, we discuss the common procedure to develop and validate biosensors for relevant biomedical and environmental purposes and future perspectives in terms of boosting capabilities and sensor integration in point-of-care platforms. © 2021 Author(s).

  • Real-time monitoring of fenitrothion in water samples using a silicon nanophotonic biosensor

    Ramirez-Priego P., Estévez M.-C., Díaz-Luisravelo H.J., Manclús J.J., Montoya Á., Lechuga L.M. Analytica Chimica Acta; 1152 (338276) 2021. 10.1016/j.aca.2021.338276. IF: 6.558

    Due to the large quantities of pesticides extensively used and their impact on the environment and human health, a prompt and reliable sensing technique could constitute an excellent tool for in-situ monitoring. With this aim, we have applied a highly sensitive photonic biosensor based on a bimodal waveguide interferometer (BiMW) for the rapid, label-free, and specific quantification of fenitrothion (FN) directly in tap water samples. After an optimization protocol, the biosensor achieved a limit of detection (LOD) of 0.29 ng mL−1 (1.05 nM) and a half-maximal inhibitory concentration (IC50) of 1.71 ng mL−1 (6.09 nM) using a competitive immunoassay and employing diluted tap water. Moreover, the biosensor was successfully employed to determine FN concentration in blind tap water samples obtaining excellent recovery percentages with a time-to-result of only 20 min without any sample pre-treatment. The features of the biosensor suggest its potential application for real time, fast and sensitive screening of FN in water samples as an analytical tool for the monitoring of the water quality. © 2021 Elsevier B.V.


  • A compact SPR biosensor device for the rapid and efficient monitoring of gluten-free diet directly in human urine

    Peláez E.C., Estevez M.-C., Domínguez R., Sousa C., Cebolla A., Lechuga L.M. Analytical and Bioanalytical Chemistry; 2020. 10.1007/s00216-020-02616-6. IF: 3.637

    Celiac disease (CD) is a chronic autoimmune disorder induced in genetically susceptible individuals by the ingestion of gluten from wheat, rye, barley, or certain varieties of oats. A careful diet follow-up is necessary to avoid health complications associated with long-term gluten intake by the celiac patients. Small peptides (GIP, gluten immunogenic peptides) derived from gluten digestion, which are excreted in the urine and feces, have emerged as promising biomarkers to monitor gluten intake. We have implemented a simple and sensitive label-free point-of-care (POC) device based on surface plasmon resonance for the direct detection of these biomarkers in urine. The assay employs specific monoclonal antibodies and has been optimized for the detection of the 33-mer α2-gliadin, known as the main immunogenic peptide of wheat gluten, and for the detection of GIP. Direct detection in undiluted urine has been accomplished by using biosensing chips containing a robust and stable biorecognition layer, obtained after carefully optimizing the biofunctionalization protocol. Excellent limits of detection have been reached (1.6–4.0 ng mL−1 using mAb G12 and A1, respectively), which ensures the detection of gluten peptides even when the gluten intake is around the maximum tolerable amount in the digestive tract (< 50 mg) for celiac individuals. No sample pretreatment, extraction, or dilution is required, and the analysis takes less than 15 min. The assays have excellent reproducibility‚ as demonstrated by measuring spiked urine samples containing the same target concentration using different biofunctionalized chips prepared and stored at different periods of time (i.e., CV% of 3.58% and 11.30%, for G12- and A1-based assays, respectively). The assay has been validated with real samples. These features pave the way towards an end-user easy-to-handle biosensor device for the rapid monitoring of gluten-free diet (GFD) and follow-up of the health status in celiac patients. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.

  • Coherent silicon photonic interferometric biosensor with an inexpensive laser source for sensitive label-free immunoassays

    Leuermann J., Stamenkovic V., Ramirez-Priego P., Sánchez-Postigo A., Fernández-Gavela A., Chapman C.A., Bailey R.C., Lechuga L.M., Perez-Inestrosa E., Collado D., Halir R., Molina-Fernández Í. Optics Letters; 45 (24) 2020. 10.1364/OL.411635. IF: 3.714

    Over the past two decades, integrated photonic sensors have been of major interest to the optical biosensor community due to their capability to detect low concentrations of molecules with label-free operation. Among these, interferometric sensors can be read-out with simple, fixed-wavelength laser sources and offer excellent detection limits but can suffer from sensitivity fading when not tuned to their quadrature point. Recently, coherently detected sensors were demonstrated as an attractive alternative to overcome this limitation. Here we show, for the first time, to the best of our knowledge, that this coherent scheme provides sub-nanogram per milliliter limits of detection in C-reactive protein immunoassays and that quasi-balanced optical arm lengths enable operation with inexpensive Fabry–Perot-type lasers sources at telecom wavelengths. © 2020 Optical Society of America

  • Detection and Quantification of HspX Antigen in Sputum Samples Using Plasmonic Biosensing: Toward a Real Point-of-Care (POC) for Tuberculosis Diagnosis

    Peláez E.C., Estevez M.C., Mongui A., Menéndez M.-C., Toro C., Herrera-Sandoval O.L., Robledo J., García M.J., Portillo P.D., Lechuga L.M. ACS infectious diseases; 6 (5): 1110 - 1120. 2020. 10.1021/acsinfecdis.9b00502. IF: 4.614

    Advancements that occurred during the last years in the diagnosis of Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis infection, have prompted increased survival rates of patients. However, limitations related to the inefficiency of an early detection still remain; some techniques and laboratory methods do not have enough specificity and most instruments are expensive and require handling by trained staff. In order to contribute to a prompt and effective diagnosis of tuberculosis, we report the development of a portable, user-friendly, and low-cost biosensor device for its early detection. By using a label-free surface plasmon resonance (SPR) biosensor, we have established a direct immunoassay for the direct detection and quantification of the heat shock protein X (HspX) of Mtb, a well-established biomarker of this pathogen, directly in pretreated sputum samples. The method relies on highly specific monoclonal antibodies that are previously immobilized on the plasmonic sensor surface. This technology allows for the direct detection of the biomarker without amplification steps, showing a limit of detection (LOD) of 0.63 ng mL-1 and a limit of quantification (LOQ) of 2.12 ng mL-1. The direct analysis in pretreated sputum shows significant differences in the HspX concentration in patients with tuberculosis (with concentration levels in the order of 116-175 ng mL-1) compared with non-tuberculosis infected patients (values below the LOQ of the assay).

  • Fast and accurate pneumocystis pneumonia diagnosis in human samples using a label-free plasmonic biosensor

    Calvo-Lozano O., Aviñó A., Friaza V., Medina-Escuela A., Huertas C.S., Calderón E.J., Eritja R., Lechuga L.M. Nanomaterials; 10 (6, 1246): 1 - 18. 2020. 10.3390/NANO10061246. IF: 4.324

    Pneumocystis jirovecii is a fungus responsible for human Pneumocystis pneumonia, one of the most severe infections encountered in immunodepressed individuals. The diagnosis of Pneumocystis pneumonia continues to be challenging due to the absence of specific symptoms in infected patients. Moreover, the standard diagnostic method employed for its diagnosis involves mainly PCR-based techniques, which besides being highly specific and sensitive, require specialized personnel and equipment and are time-consuming. Our aim is to demonstrate an optical biosensor methodology based on surface plasmon resonance to perform such diagnostics in an efficient and decentralized scheme. The biosensor methodology employs poly-purine reverse-Hoogsteen hairpin probes for the detection of the mitochondrial large subunit ribosomal RNA (mtLSU rRNA) gene, related to P. jirovecii detection. The biosensor device performs a real-time and label-free identification of the mtLSU rRNA gene with excellent selectivity and reproducibility, achieving limits of detection of around 2.11 nM. A preliminary evaluation of clinical samples showed rapid, label-free and specific identification of P. jirovecii in human lung fluids such as bronchoalveolar lavages or nasopharyngeal aspirates. These results offer a door for the future deployment of a sensitive diagnostic tool for fast, direct and selective detection of Pneumocystis pneumonia disease. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.

  • How Nanophotonic Label-Free Biosensors Can Contribute to Rapid and Massive Diagnostics of Respiratory Virus Infections: COVID-19 Case

    Soler M., Estevez M.C., Cardenosa-Rubio M., Astua A., Lechuga L.M. ACS Sensors; 5 (9): 2663 - 2678. 2020. 10.1021/acssensors.0c01180. IF: 7.333

    The global sanitary crisis caused by the emergence of the respiratory virus SARS-CoV-2 and the COVID-19 outbreak has revealed the urgent need for rapid, accurate, and affordable diagnostic tests to broadly and massively monitor the population in order to properly manage and control the spread of the pandemic. Current diagnostic techniques essentially rely on polymerase chain reaction (PCR) tests, which provide the required sensitivity and specificity. However, its relatively long time-to-result, including sample transport to a specialized laboratory, delays massive detection. Rapid lateral flow tests (both antigen and serological tests) are a remarkable alternative for rapid point-of-care diagnostics, but they exhibit critical limitations as they do not always achieve the required sensitivity for reliable diagnostics and surveillance. Next-generation diagnostic tools capable of overcoming all the above limitations are in demand, and optical biosensors are an excellent option to surpass such critical issues. Label-free nanophotonic biosensors offer high sensitivity and operational robustness with an enormous potential for integration in compact autonomous devices to be delivered out-of-the-lab at the point-of-care (POC). Taking the current COVID-19 pandemic as a critical case scenario, we provide an overview of the diagnostic techniques for respiratory viruses and analyze how nanophotonic biosensors can contribute to improving such diagnostics. We review the ongoing published work using this biosensor technology for intact virus detection, nucleic acid detection or serological tests, and the key factors for bringing nanophotonic POC biosensors to accurate and effective COVID-19 diagnosis on the short term. Copyright © 2020 American Chemical Society.

  • Label-free detection of nosocomial bacteria using a nanophotonic interferometric biosensor

    Maldonado J., Estévez M.-C., Fernández-Gavela A., González-López J.J., González-Guerrero A.B., Lechuga L.M. Analyst; 145 (2): 497 - 506. 2020. 10.1039/c9an01485c. IF: 3.978

    Nosocomial infections are a major concern at the worldwide level. Early and accurate identification of nosocomial pathogens is crucial to provide timely and adequate treatment. A prompt response also prevents the progression of the infection to life-threatening conditions, such as septicemia or generalized bloodstream infection. We have implemented two highly sensitive methodologies using an ultrasensitive photonic biosensor based on a bimodal waveguide interferometer (BiMW) for the fast detection of Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA), two of the most prevalent bacteria associated with nosocomial infections. For that, we have developed a biofunctionalization strategy based on the use of a PEGylated silane (silane-PEG-COOH) which provides a highly resistant and bacteria-repelling surface, which is crucial to specifically detect each bacterium. Two different biosensor assays have been set under standard buffer conditions: One based on a specific direct immunoassay employing polyclonal antibodies for the detection of P. aeruginosa and another one employing aptamers for the direct detection of MRSA. The biosensor immunoassay for P. aeruginosa is fast (it only takes 12 min) and specific and has experimentally detected concentrations down to 800 cfu mL-1 (cfu: Colony forming unit). The second one relies on the use of an aptamer that specifically detects penicillin-binding protein 2a (PBP2a), a protein only expressed in the MRSA mutant, providing a photonic biosensor with the ability to identify the resistant pathogen MRSA and differentiate it from methicillin-susceptible S. aureus (MSSA). Direct, label-free, and selective detection of whole MRSA bacteria has been achieved, making possible the direct detection of also 800 cfu mL-1. According to the signal-to-noise (S/N) ratio of the device, a theoretical limit of detection (LOD) of around 49 and 29 cfu mL-1 was estimated for P. aeruginosa and MRSA, respectively. Both results obtained under standard conditions reveal the great potential this interferometric biosensor device has as a versatile and specific tool for bacterial detection and quantification, providing a rapid method for the identification of nosocomial pathogens within the clinical requirements of sensitivity for the diagnosis of infections. © 2020 The Royal Society of Chemistry.

  • Low Limit of Detection Silicon Photonic Sensor with Extremely-Low-Cost Laser Source

    Leuermann J., Fernandez-Gavela A., Lechuga L.M., Sanchez-Postigo A., Halir R., Molina-Fernandez I. 2020 IEEE Photonics Conference, IPC 2020 - Proceedings; (9252217) 2020. 10.1109/IPC47351.2020.9252217. IF: 0.000

    Integrated photonic biosensors have demonstrated low bulk detection limits down to 10-7 refractive index units. Nevertheless, most rely on expensive optical sources, such as DFB lasers. Here, we experimentally demonstrate that with adequate sensor design comparable detection limits are achievable with a low-cost Fabry-Perot laser. © 2020 IEEE.

  • Microfluidic cartridge for LAM-based TB poc-diagnostics using silicon photonics sensor

    Becker H., Singh M., Lechuga L., Bockstaele R., Anton B., Martens D., Gonzalez-Guerrero A., Vos R., Elamin A., Bienstman P. 21st International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2017; : 1269 - 1270. 2020. . IF: 0.000

    This paper presents a cartridge for a urine-based point-of-care test for Tuberculosis (TB). It utilizes a silicon photonics sensor for detection, sensing changes in refractive index based on the binding of the relevant biomarkers present in urine of TB patients. The device shows a significant improvement in sensitivity compared to the currently existing lateral flow TB tests. © 17CBMS-0001.

  • Nanophotonic biosensors: Driving personalized medicine

    Soler M., Calvo-Lozano O., Carmen Estevez M., Lechuga L.M. Optics and Photonics News; 31 (4): 25 - 31. 2020. 10.1364/OPN.31.4.000024. IF: 0.000

    [No abstract available]

  • One-Step Immobilization of Antibodies and DNA on Gold Sensor Surfaces via a Poly-Adenine Oligonucleotide Approach

    Huertas C.S., Soler M., Estevez M.-C., Lechuga L.M. Analytical Chemistry; 92 (18): 12596 - 12604. 2020. 10.1021/acs.analchem.0c02619. IF: 6.785

    Label-free plasmonic biosensors have demonstrated promising capabilities as analytical tools for the detection of virtually any type of biomarker. They are presented as good candidates for precision diagnostics since they offer highly sensitive, cost-effective solutions that can be used in any clinical or laboratory setting without the need for specialized trainees. However, different surface functionalization protocols are required, depending on the nature of the biorecognition element, limiting their capabilities for integrated multi-biomarker detection. Here, we present a simple, yet efficient, one-step immobilization approach that is common for both DNA probes and antibodies. Our immobilization approach relies on the incorporation of poly-adenine (polyA) blocks in both nucleic acid probes and antibodies. PolyA sequences have a remarkable affinity for gold surfaces and can specifically interact with sufficient strength to generate stable, dense, and highly ordered monolayers. We have demonstrated excellent performance of our universal functionalization method, showing limits of detection and quantification in the pM-nM range. Moreover, it was able to reduce up to 50% of the background signal from undiluted serum samples compared to conventional methods, demonstrating the immense potential of this strategy for the direct analysis of human biofluids, essential for rapid point-of-care diagnostics. The polyA-based immobilization approach is a promising alternative for the generation of multiplexed biosensors that can detect both protein and nucleic acid biomarkers for multiparametric diagnostic assays. Copyright © 2020 American Chemical Society.

  • Optical nanogap antennas as plasmonic biosensors for the detection of miRNA biomarkers

    Portela A., Calvo-Lozano O., Estevez M., Medina Escuela A., Lechuga L.M. Journal of Materials Chemistry B; 8 (19): 4310 - 4317. 2020. 10.1039/d0tb00307g. IF: 5.344

    Nanoplasmonic biosensors based on nanogap antenna structures usually demand complex and expensive fabrication processes in order to achieve a good performance and sensitive detection. We here report the fabrication of large-area nanoplasmonic sensor chips based on nanogap antennas by employing a customized, simple and low-cost colloidal lithography process. By precisely controlling the angle for tilted e-beam metal evaporation, an elliptical mask is produced, which defines the total length of the dipole antenna nanostructures while assuring that the plasmonic response is oriented in the same direction along the sensor chip. Large-area sensor chips of nanogap antennas formed by pairs of gold nanodisks separated by gaps with an average size of 11.6 ± 4.7 nm are obtained. The optical characterization of the nanogap antenna structures in an attenuated total reflection (ATR) configuration shows a bulk refractive index sensitivity of 422 nm per RIU, which is in agreement with FDTD numerical simulations. The biosensing potential of the cm2-sized nanostructured plasmonic sensor chips has been evaluated for the detection of miRNA-210, a relevant biomarker for lung cancer diagnosis, through a DNA/miRNA hybridization assay. A limit of detection (LOD) of 0.78 nM (5.1 ng mL-1) was achieved with no need of further amplification steps, demonstrating the high sensitivity of these plasmonic nanogap antennas for the direct and label-free detection of low molecular weight biomolecules such as miRNAs. © The Royal Society of Chemistry 2020.

  • Silicon photonic label free biosensors with coherent readout

    Leuermann J., Fernandez-Gavela A., Halir R., Ortega-Monux A., Wanguemert-Perez J.G., Lechuga L.M., Molina-Fernandez I. International Conference on Transparent Optical Networks; 2020-July (9203519) 2020. 10.1109/ICTON51198.2020.9203519. IF: 0.000

    Silicon photonics enables sensitive and label-free optical biosensors for the detection of chemical and biological substances. Different sensing architectures have been used to improve the limit of detection and increase the dynamic range response. Here, we show experimental limit of detection at state-of-the-art level using silicon nitride integrated Mach-Zehnder interferometers with coherent read-out. These preliminary results are concordant with theoretical results, showing that the proposed approach enables the use of simple read-out equipment using low-cost laser sources. © 2020 IEEE.

  • Ultrasensitive label-free detection of unamplified multidrug-resistance bacteria genes with a bimodal waveguide interferometric biosensor

    Maldonado J., González-Guerrero A.B., Fernández-Gavela A., González-López J.J., Lechuga L.M. Diagnostics; 10 (10, 845) 2020. 10.3390/diagnostics10100845. IF: 3.110

    Infections by multidrug-resistant bacteria are becoming a major healthcare emergence with millions of reported cases every year and an increasing incidence of deaths. An advanced diagnostic platform able to directly detect and identify antimicrobial resistance in a faster way than conventional techniques could help in the adoption of early and accurate therapeutic interventions, limiting the actual negative impact on patient outcomes. With this objective, we have developed a new biosensor methodology using an ultrasensitive nanophotonic bimodal waveguide interferometer (BiMW), which allows a rapid and direct detection, without amplification, of two prevalent and clinically relevant Gram-negative antimicrobial resistance encoding sequences: the extended-spectrum betalactamase-encoding gene blaCTX-M-15 and the carbapenemase-encoding gene blaNDM-5 We demonstrate the extreme sensitivity and specificity of our biosensor methodology for the detection of both gene sequences. Our results show that the BiMW biosensor can be employed as an ultrasensitive (attomolar level) and specific diagnostic tool for rapidly (less than 30 min) identifying drug resistance. The BiMW nanobiosensor holds great promise as a powerful tool for the control and management of healthcare-associated infections by multidrug-resistant bacteria. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.


  • Advanced Evanescent-Wave Optical Biosensors for the Detection of Nucleic Acids: An Analytic Perspective

    Huertas C.S., Calvo-Lozano O., Mitchell A., Lechuga L.M. Frontiers in Chemistry; 7 (724) 2019. 10.3389/fchem.2019.00724. IF: 3.782

    Evanescent-wave optical biosensors have become an attractive alternative for the screening of nucleic acids in the clinical context. They possess highly sensitive transducers able to perform detection of a wide range of nucleic acid-based biomarkers without the need of any label or marker. These optical biosensor platforms are very versatile, allowing the incorporation of an almost limitless range of biorecognition probes precisely and robustly adhered to the sensor surface by covalent surface chemistry approaches. In addition, their application can be further enhanced by their combination with different processes, thanks to their integration with complex and automated microfluidic systems, facilitating the development of multiplexed and user-friendly platforms. The objective of this work is to provide a comprehensive synopsis of cutting-edge analytical strategies based on these label-free optical biosensors able to deal with the drawbacks related to DNA and RNA detection, from single point mutations assays and epigenetic alterations, to bacterial infections. Several plasmonic and silicon photonic-based biosensors are described together with their most recent applications in this area. We also identify and analyse the main challenges faced when attempting to harness this technology and how several innovative approaches introduced in the last years manage those issues, including the use of new biorecognition probes, surface functionalization approaches, signal amplification and enhancement strategies, as well as, sophisticated microfluidic solutions. © Copyright © 2019 Huertas, Calvo-Lozano, Mitchell and Lechuga.

  • Advances in nanoplasmonic biosensors for clinical applications

    Mauriz E., Dey P., Lechuga L.M. Analyst; 144 (24): 7105 - 7129. 2019. 10.1039/c9an00701f. IF: 4.019

    Biomarkers are unquestionable biological indicators for diagnosis and therapeutic interventions providing appropriate classification of a wide range of health disorders and risk factors. Nonetheless, the detection and quantification of biomarkers need to be tested with sufficient reliability by robust analytical methods in order to assure clinical performance in health care settings. Since the analytical performance is determined by the sensitivity and specificity of the method employed, techniques have been intensively refined in order to avoid the misinterpretation of results and undesirable bias. Although biomarkers can be detected with the existing analytical techniques, to reproducibly quantify them in decentralized settings or remote locations with the required accuracy is still a challenge. Currently, only a few point-of-care devices for biomarker evaluation are commercially available. Thus, more focused research efforts are needed to overcome these limitations in order to provide universal patient-centered care platforms. To this end, plasmonic biosensors can be conveniently used as portable diagnostic devices for attaining timely and cost-effective clinical outcomes. The development of enhanced performance based on nanoplasmonics technology opens the way for sensor miniaturization, multiplexing and point of care testing. This review covers recent advances and applications of plasmonic and nanoplasmonic biosensors intended for biomarker diagnosis in clinical practice, including cancer, cardiovascular and neurodegenerative diseases. The review specially focuses on: (i) recent progress in plasmonics development including the design of singular nanostructured surfaces, (ii) novel chemical functionalization strategies for the appropriate incorporation of bioreceptors and (iii) plasmonic applications as real operative devices in the clinical field. Future prospects in the use of nanoplasmonic sensor platforms for personalised quantification and management of biomarkers directly in body fluids will also be discussed. © 2019 The Royal Society of Chemistry.

  • Aptamer-peptide conjugates as a new strategy to modulate human α-thrombin binding affinity

    Aviñó A., Jorge A.F., Huertas C.S., Cova T.F.G.G., Pais A., Lechuga L.M., Eritja R., Fabrega C. Biochimica et Biophysica Acta - General Subjects; 1863 (10): 1619 - 1630. 2019. 10.1016/j.bbagen.2019.06.014. IF: 3.681

    Aptamers are single-stranded RNA or DNA molecules that specifically recognize their targets and have proven valuable for functionalizing sensitive biosensors. α-thrombin is a trypsin-like serine proteinase which plays a crucial role in haemostasis and thrombosis. An abnormal activity or overexpression of this protein is associated with a variety of diseases. A great deal of attention was devoted to the construction of high-throughput biosensors for accurately detect thrombin for the early diagnosis and treatment of related diseases. Herein, we propose a new approach to modulate the interaction between α-thrombin and the aptamer TBA15. To this end, TBA15 was chemically conjugated to two peptide sequences (TBA-G3FIE-Ac and TBA-G3EIF-Ac) corresponding to a short fragment of the acidic region of the human factor V, which is known to interact directly with exosite I. Surface Plasmon Resonance (SPR) results showed enhanced analytical performances of thrombin with TBA-G3EIF-Ac than with TBA wild-type, reaching a limit of detection as low as 44.9 pM. Electrophoresis mobility shift assay (EMSA) corroborated the SPR results. Molecular dynamics (MD) simulations support experimental evidences and provided further insight into thrombin/TBA-peptide interaction. Our findings demonstrate that the combination of TBA15 with key interacting peptides offers good opportunities to produce sensitive devices for thrombin detection and potential candidates to block thrombin activity. © 2019 Elsevier B.V.

  • Boosting cancer immunotherapy with optical biosensor nanotechnologies

    M. Soler and L. M. Lechuga European Medical Journal; 4 (4): 124 - 132. 2019. .

  • Building of a flexible microfluidic plasmo-nanomechanical biosensor for live cell analysis

    Solis-Tinoco V., Marquez S., Quesada-Lopez T., Villarroya F., Homs-Corbera A., Lechuga L.M. Sensors and Actuators, B: Chemical; 291: 48 - 57. 2019. 10.1016/j.snb.2019.04.038. IF: 6.393

    Biosensor devices can constitute an advanced tool for monitoring and study complex dynamic biological processes, as for example cellular adhesion. Cellular adhesion is a multipart process with crucial implications in physiology (i.e. immune response, tissue nature, architecture maintenance, or behaviour and expansion of tumor cells). This work focuses on offering a controlled methodology in order to fabricate a flexible plasmo-nanomechanical biosensor placed within a microfluidic channel as a new tool for future cell adhesion studies. We designed, fabricated, and optically and mechanically characterized this novel optical biosensor. As a proof-of-concept of its functionality, the biosensor was employed to observe fibroblasts adhesion in a cell culture. The device is configured by an hexagonal array of flexible rigid/soft polymeric nanopillars capped with plasmonic gold nanodisks integrated inside a microfluidic channel. The fabrication employs low-cost and large-scale replica molding techniques using two different polymers materials (EPOTECK OG142 and 310 M). By using those materials the spring constant of the polymer nanopillars (k) can be fabricated from 1.19E-02 [N/m] to 5.35E+00 [N/m] indicating different mechanical sensitivities to shear stress. Therefore, the biosensor has the feasibility to mimic soft and rigid tissues important for the description of cellular nanoscale behaviours. The biosensor exhibits a suitable bulk sensitivity of 164 nm or 206 nm/refractive index unit respectively, depending on the base material. The range of calculated forces goes from ≈1.98 nN to ≈.942 μN. This supports that the plasmo-nanomechanical biosensors could be employed as novel tool to study living cells behavior. © 2019

  • Early sepsis diagnosis via protein and miRNA biomarkers using a novel point-of-care photonic biosensor

    Fabri-Faja N., Calvo-Lozano O., Dey P., Terborg R.A., Estevez M.-C., Belushkin A., Yesilköy F., Duempelmann L., Altug H., Pruneri V., Lechuga L.M. Analytica Chimica Acta; 1077: 232 - 242. 2019. 10.1016/j.aca.2019.05.038. IF: 5.256

    Sepsis is a condition characterized by a severe stage of blood-infection often leading to tissue damage, organ failure and finally death. Fast diagnosis and identification of the sepsis stage (sepsis, severe sepsis or septic shock) is critical for the patient's evolution and could help in defining the most adequate treatment in order to reduce its mortality. The combined detection of several biomarkers in a timely, specific and simultaneous way could ensure a more accurate diagnosis. We have designed a new optical point-of-care (POC) device based on a phase-sensitive interferometric biosensor with a label-free microarray configuration for potential high-throughput evaluation of specific sepsis biomarkers. The sensor chip, which relies on the use of metallic nanostructures, provides versatility in terms of biofunctionalization, allowing the efficient immobilization of different kind of receptors such as antibodies or oligonucleotides. We have focused on two structurally different types of biomarkers: proteins, including C-reactive protein (CRP) and Interleukin 6 (IL6), and miRNAs, using miRNA-16 as an example. Limits of Detection (LoD) of 18 μg mL−1, 88 μg mL−1 and 1 μM (6 μg mL−1) have been respectively obtained for CRP, IL6 and miRNA-16 in individual assays, with high accuracy and reproducibility. The multiplexing capabilities have also been assessed with the simultaneous analysis of both protein biomarkers. © 2019 Elsevier B.V.

  • Full integration of photonic nanoimmunosensors in portable platforms for on-line monitoring of ocean pollutants

    Fernández-Gavela A., Herranz S., Chocarro B., Falke F., Schreuder E., Leeuwis H., Heideman R.G., Lechuga L.M. Sensors and Actuators, B: Chemical; 297 (126758) 2019. 10.1016/j.snb.2019.126758. IF: 6.393

    We have developed a photonic nano-immunosensor platform for the on-site analysis of harmful organic ocean pollutants, intended to be allocated in stand-alone buoys. The main aim is bringing the monitoring tools directly to the contaminated place, resulting in cost and time savings as compared to the standard analytical techniques. As sensor we have employed an integrated asymmetric Mach-Zehnder interferometer (aMZI) of micro/nano dimensions, based on silicon photonic technology. In order to obtain a multiplexed system, a four-channel microfluidic cell has been designed, manufactured and incorporated in the miniaturized sensor. Additionally, a microfluidic delivery module enabling automatic sample analysis has been designed, evaluated and assembled. Moreover, we have implemented the optical interconnections of the sensor chip by fiber optics, as well the electronics and the required software and data processing. Pollutant detection is based on a competitive immunoassay using bioreceptors previously biofunctionalized on the aMZI sensor arms and incubation with a specific antibody. As proof of concept, two types of pollutants have been analysed: the biocide Irgarol 1051, and the antibiotic Tetracycline. Results show limits of detection in the range of few ng/mL, accomplished the European legislation. © 2019 Elsevier B.V.

  • Label-free Bacteria Quantification in Blood Plasma by a Bioprinted Microarray Based Interferometric Point-of-Care Device

    Dey P., Fabri-Faja N., Calvo-Lozano O., Terborg R.A., Belushkin A., Yesilkoy F., Fàbrega A., Ruiz-Rodriguez J.C., Ferrer R., González-López J.J., Estévez M.C., Altug H., Pruneri V., Lechuga L.M. ACS Sensors; 4 (1): 52 - 60. 2019. 10.1021/acssensors.8b00789. IF: 6.944

    Existing clinical methods for bacteria detection lack speed, sensitivity, and, importantly, point-of-care (PoC) applicability. Thus, finding ways to push the sensitivity of clinical PoC biosensing technologies is crucial. Here we report a portable PoC device based on lens-free interferometric microscopy (LIM). The device employs high performance nanoplasmonics and custom bioprinted microarrays and is capable of direct label-free bacteria (E. coli) quantification. With only one-step sample handling we offer a sample-to-data turnaround time of 40 min. Our technology features detection sensitivity of a single bacterial cell both in buffer and in diluted blood plasma and is intrinsically limited by the number of cells present in the detection volume. When employed in a hospital setting, the device has enabled accurate categorization of sepsis patients (infectious SIRS) from control groups (healthy individuals and noninfectious SIRS patients) without false positives/negatives. User-friendly on-site bacterial clinical diagnosis can thus become a reality. © 2018 American Chemical Society.

  • Label-Free Nanoplasmonic Biosensing of Cancer Biomarkers for Clinical Diagnosis

    Portela A., Peláez E.C., Calvo-Lozano O., Estévez M.C., Lechuga L.M. Methods in Molecular Biology; 2027: 115 - 140. 2019. 10.1007/978-1-4939-9616-2_10.

    Biosensing of cancer biomarkers enabling early diagnosis of cancer constitutes an essential tool for clinical intervention and application of novel therapies against cancer disease. Optical biosensor instruments as point-of-care (POC) devices and operating under label-free scheme have demonstrated to provide fast, simple, and high-sensitivity assays even at home care environment. Nanoplasmonic biosensors are thought to be a powerful tool for detection of complex analytes of relevant clinical applications. Using high-throughput fabrication techniques, large surface patterned with gold nanodisk structures is obtained showing surface sensitivities with limit of detection (LOD) in the order of picomolar concentration range. Here, we describe two major assay methodologies used for detection of lung and colorectal cancer, respectively. Particularly, we have selected a complementary hybridization DNA/RNA assay for the assessment of two miRNAs (miRNA-210 and miRNA-205) for detection of lung cancer. However, for colorectal cancer we present the detection of four tumor-associated antigen (TAA) biomarkers (MAPKAPK3, PIM-1, STK4, and GTF2B) as possible TAA targets for autoantibody production. Strategies for detecting these biomarkers in real samples such as serum are also presented, demonstrating the capabilities of these assays to be transferred to real clinical settings. © Springer Science+Business Media, LLC, part of Springer Nature 2019.

  • Label-free plasmonic biosensors for point-of-care diagnostics: a review

    Soler M., Huertas C.S., Lechuga L.M. Expert Review of Molecular Diagnostics; 19 (1): 71 - 81. 2019. 10.1080/14737159.2019.1554435. IF: 3.099

    Introduction: Optical biosensors, particularly those based on nanoplasmonics technology, have emerged in recent decades as a potential solution for disease diagnostics and therapy follow-up at the point-of-care (POC). These biosensor platforms could overcome some of the challenges faced in conventional diagnosis techniques offering label-free assays with immediate results and employing small and user-friendly devices. Areas covered: In this review, we will provide a critical overview of the recent advances in the development of nanoplasmonic biosensors for the POC diagnostics. We focus on those systems with demonstrated capabilities for integration in portable platforms, highlighting some of the most relevant diagnostics applications targeting proteins, nucleic acids, and cells as disease biomarkers. Expert commentary: Despite the attractive features of label-free nanoplasmonic sensors in terms of miniaturization and analytical robustness, the route toward an effective clinical implementation involves the integration of fully automated microfluidic systems for sample processing and analysis, and the optimization of surface biofunctionalization procedures. Additionally, the development of multiplexed sensors for high-throughput analysis and including specific neoantigens and novel biomarkers in detection panels will provide the means for delivering a powerful analytical technology for an accurate and improved medical diagnosis. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.

  • Label-free, scalable and point-of-care imaging platform for rapid analysis of biomarker

    L. Duempelmann, R. A. Terborg, J. Pello, I. Mannelli, F. Yesilkoy, A. A. Belushkin, Y. Jahani, N. Fabri-Faja, P. Dey, O. Calvo-Lozano, M. -. Estevez, A. Fàbrega, J. J. González-López, L. M. Lechuga, H. Altug, and V. Pruneri SPIE Proceedings (Optical Society of America, 2019); Clinical and Preclinical Optical Diagnostics II, V 2019. 10.1117/12.2525878.

    We propose a disruptive point-of-care (PoC) imaging platform based on lens-free interference phase-contrast imaging for rapid detection of biomarker such as for sepsis and potentially other diseases (e.g. cancer). It enables simultaneous analysis of potentially up to 10,000 functionalized microarray spots with different biomarkers with fast time-to-results (few minutes) and by consuming a small sample volume (~10 µL). The high sensitivity allows direct measurements of the biomarker binding without the use of fluorescent labels (e.g. ELISA) or microbial culture methods. In addition, ad-hoc plasmonic nano-structuring is utilized to significantly improve the sensitivity for biomarker detection (optical path difference ~Å) to concentration levels relevant for disease diagnosis. The proposed technology incorporates a portable and low-cost lens-free imaging reader made of consumer electronic components, plasmonic microarrays with distinct functionalization, and user-friendly software based on a novel phase-shifting interferometry method for topography and refractive index analysis. Due to its compactness and cost-efficiency, we foresee a great potential for PoC applications, especially for the rapid detection of infectious diseases or life-threatening conditions, e.g. sepsis, but also for clinical trials of drugs and food control.

  • Low-cost and portable UV holographic microscope for high-contrast protein crystal imaging

    Daloglu M.U., Ray A., Collazo M.J., Brown C., Tseng D., Chocarro-Ruiz B., Lechuga L.M., Cascio D., Ozcan A. APL Photonics; 4 (3, 030804) 2019. 10.1063/1.5080158. IF: 4.383

    Imaging protein crystals and distinguishing them from salt crystals is an important task for protein crystallographers. The conventional tool used for this purpose is a dual-mode microscope composed of bright-field and ultraviolet (UV) induced fluorescence modes. The distinction between a protein and a salt crystal is made based upon the fluorescence response to the UV excitation, where most protein crystals absorb the UV excitation and emit fluorescence, unlike salt crystals. These dual-mode optical microscopes are sensitive; however, they are relatively bulky and expensive as they require UV-grade optics. As an alternative, here we demonstrate that on-chip UV holographic imaging offers a low-cost, portable, and robust technique to image and distinguish protein crystals from salt crystals, without the need for any expensive and bulky optical components. Only composed of a UV light-emitting-diode at 280 nm and a consumer-grade complementary metal-oxide-semiconductor image sensor de-capped and interfaced to a Raspberry Pi single-board computer, the necessary information from the crystal samples (placed very close to the sensor active area) is captured in the form of in-line holograms and extracted through digital back-propagation. In these holographic amplitude reconstructions, protein crystals appear significantly darker compared to the background due to the strong UV absorption, unlike salt crystals which do not show any contrast, enabling us to clearly distinguish between them. We believe that the on-chip UV holographic microscope could serve as a low-cost, sensitive, and robust alternative to conventional lens-based UV-microscopes used in protein crystallography. © 2019 Author(s).

  • Low-cost vertical taper for highly efficient light in-coupling in bimodal nanointerferometric waveguide biosensors

    Daniel Grajales, Adrián Fernández Gavela, Carlos Domínguez, Jose Ramón Sendra, Laura M Lechuga Journal of Physics: Photonics; 1 (2): 25002. 2019. 10.1088/2515-7647/aafebb. IF: 0.000

    There is still the need for a compact and cost-effective solution for efficient light in-coupling in integrated waveguides employed in photonic biosensors, especially when these waveguides are of submicron dimensions and operate at visible wavelengths. The employment of a vertically stacked taper with a larger input area is proposed to meet this need. The design of the taper is divided into two stages: in the first stage, light is guided downwards by two vertically stacked tapers; in the second stage, an inverted taper directly confines the light inside the waveguide. The design parameters are optimized using commercial software, obtaining a total theoretical light coupling efficiency of 72.25%. The taper is manufactured using SU-8 polymer as the main material, employing standard photolithography techniques at wafer level. After characterization, the results show the practicality of the taper when coupling light from macrometric sources to nanometric waveguides, obtaining an experimental coupling efficiency of 55%. With this vertical taper, a compact, easy-to-couple and cost-effective solution is achieved for waveguide-based biosensors operating at visible wavelengths, opening the way for a truly portable point-of-care biosensor for low-cost and label-free diagnostics.

  • Optimization study of bimodal waveguide interferometric biosensors

    Grajales D., Lechuga L.M. Proceedings 2015 European Conference on Lasers and Electro-Optics - European Quantum Electronics Conf; 2019. . IF: 0.000

    [No abstract available]

  • Optimizing the limit of detection of waveguide-based interferometric biosensor devices

    Leuermann J., Fernández-Gavela A., Torres-Cubillo A., Postigo S., Sánchez-Postigo A., Lechuga L.M., Halir R., Molina-Fernández Í. Sensors (Switzerland); 19 (17, 3671) 2019. 10.3390/s19173671. IF: 3.031

    Waveguide-based photonic sensors provide a unique combination of high sensitivity, compact size and label-free, multiplexed operation. Interferometric configurations furthermore enable a simple, fixed-wavelength read-out making them particularly suitable for low-cost diagnostic and monitoring devices. Their limit of detection, i.e., the lowest analyte concentration that can be reliably observed, mainly depends on the sensors response to small refractive index changes, and the noise in the read-out system. While enhancements in the sensors response have been extensively studied, noise optimization has received much less attention. Here we show that order-of-magnitude enhancements in the limit of detection can be achieved through systematic noise reduction, and demonstrate a limit of detection of ~10-8 RIU with a silicon nitride sensor operating at telecom wavelengths. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.

  • Polymer Based Trimodal Interferometric Sensor

    Ramirez J.C., Lechuga L.M., Hernandez Figueroa H.E., Gabrielli L.H. 2019 SBFoton International Optics and Photonics Conference, SBFoton IOPC 2019; (8910220) 2019. 10.1109/SBFoton-IOPC.2019.8910220.

    In this work, a polymer-based single channel trimodal interferometric sensor is presented and demonstrated. The presented device was fabricated with Direct Laser Writer Technique at 405 nm wavelength on SU-8 photoresist, showing free spectral range of 20.2 nm and signal visibility of 5.7 dB, reaching very high sensitivity to temperature variations of 0.058 dB/°C. © 2019 IEEE.

  • Preface

    Lechuga L., Raptis I., Jorge P., Cusano A. Optics and Laser Technology; 113: 35 - 36. 2019. 10.1016/j.optlastec.2018.12.006. IF: 3.319

    [No abstract available]

  • Site-Specific mRNA Cleavage for Selective and Quantitative Profiling of Alternative Splicing with Label-Free Optical Biosensors

    Huertas C.S., Bonnal S., Soler M., Escuela A.M., Valcárcel J., Lechuga L.M. Analytical Chemistry; 91 (23): 15138 - 15146. 2019. 10.1021/acs.analchem.9b03898. IF: 6.350

    Alternative splicing of mRNA precursors is a key process in gene regulation, contributing to the diversity of proteomes by the alternative selection of exonic sequences. Alterations in this mechanism are associated with most cancers, enhancing their proliferation and survival, and can be employed as cancer biomarkers. Label-free optical biosensors are ideal tools for the highly sensitive and label-free analysis of nucleic acids. However, their application for alternative splicing analysis has been hampered due to the formation of complex and intricate long-range base-pairing interactions which make the direct detection in mRNA isoforms difficult. To solve this bottleneck, we introduce a methodology for the generation of length-controlled RNA fragments from purified total RNA, which can be easily detected by the biosensor. The methodology seizes RNase H enzyme activity to degrade the upstream and downstream RNA segments flanking the target sequence upon hybridization to specific DNA oligos. It allows the fast and direct monitoring of Fas gene alternative splicing in real time, employing a surface plasmon resonance biosensor. We demonstrate the selective and specific detection of mRNA fragments in the pM-nM concentration range, reducing quantification errors and showing 81% accuracy when compared to RT-qPCR. The site-specific cleavage outperformed random RNA hydrolysis by increasing the detection accuracy by 20%, making this methodology particularly appropriate for label-free quantification of alternative splicing events in complex samples. Copyright © 2019 American Chemical Society.

  • Trimodal waveguide demonstration and its implementation as a high order mode interferometer for sensing application

    Ramirez J.C., Gabrielli L.H., Lechuga L.M., Hernandez-Figueroa H.E. Sensors (Switzerland); 19 (12, 2821) 2019. 10.3390/s19122821. IF: 3.031

    This work implements and demonstrates an interferometric transducer based on a trimodal optical waveguide concept. The readout signal is generated from the interference between the fundamental and second-order modes propagating on a straight polymer waveguide. Intuitively, the higher the mode order, the larger the fraction of power (evanescent field) propagating outside the waveguide core, hence the higher the sensitivity that can be achieved when interfering against the strongly confined fundamental mode. The device is fabricated using the polymer SU-8 over a SiO2 substrate and shows a free spectral range of 20.2 nm and signal visibility of 5.7 dB, reaching a sensitivity to temperature variations of 0.0586 dB/°C. The results indicate that the proposed interferometer is a promising candidate for highly sensitive, compact and low-cost photonic transducer for implementation in different types of sensing applications, among these, point-of-care. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.


  • A CO2 optical sensor based on self-assembled metal-organic framework nanoparticles

    Chocarro-Ruiz B., Pérez-Carvajal J., Avci C., Calvo-Lozano O., Alonso M.I., Maspoch D., Lechuga L.M. Journal of Materials Chemistry A; 6 (27): 13171 - 13177. 2018. 10.1039/c8ta02767f. IF: 9.931

    The development of devices for sensing and monitoring CO2 levels is crucial for many fields such as food packaging and for human safety indoors. Herein the fabrication of an optical CO2 sensor by integration of a metal-organic framework (MOF) onto bimodal optical waveguides is reported. This sensor is constructed via self-assembly of a transparent film of zeolitic imidazolate framework-8 (ZIF-8) nanoparticles (size: 32 ± 5 nm) on the waveguides. The nanoZIF-8-based sensor exhibits a broad linear response, with limits of detection of 3130 ppm at room temperature and 774 ppm at 278 K. Furthermore, it is robust, selective, fast and reusable, and can be stored under humid conditions with no loss in performance. © The Royal Society of Chemistry 2018.

  • A low-cost integrated biosensing platform based on SiN nanophotonics for biomarker detection in urine

    Martens D., Ramirez-Priego P., Murib M.S., Elamin A.A., Gonzalez-Guerrero A.B., Stehr M., Jonas F., Anton B., Hlawatsch N., Soetaert P., Vos R., Stassen A., Severi S., Van Roy W., Bockstaele R., Becker H., Singh M., Lechuga L.M., Bienstman P. Analytical Methods; 10 (25): 3066 - 3073. 2018. 10.1039/c8ay00666k. IF: 2.073

    We present a low-cost integrated nanophotonic lab-on-a-chip platform suitable for point-of-care (POC) biomarker analysis. The sensor chip included in the platform contains multiplexed Mach-Zehnder interferometers with an on-chip optical spectral analyser consisting of an arrayed-waveguide grating. The sensor chip is fabricated in silicon nitride material, which makes it compatible with consumer-electronics-grade sources and detectors, leading to the possibility of low-cost instrumentation. The nanophotonic sensor chip exhibits a detection limit of 6 × 10-6 RIU (Refractive Index Units), which is in the same order of magnitude as the reported values for state-of-the-art evanescent wave sensors. The sensor chip is biofunctionalised with specific bioreceptors and integrated into a polymer microfluidic cartridge. The POC instrumentation platform contains optical excitation and read-out sub-systems and dedicated on-board software for real-time analysis of patient samples. To demonstrate the versatility of the platform, we present results both on the detection of an antigen related to tuberculosis directly in urine samples using a laboratory prototype and on the detection of a protein biomarker (CRP) related to inflammation using the integrated instrument. © The Royal Society of Chemistry.

  • Gold/silver/gold trilayer films on nanostructured polycarbonate substrates for direct and label-free nanoplasmonic biosensing

    López-Muñoz G.A., Estévez M.-C., Vázquez-García M., Berenguel-Alonso M., Alonso-Chamarro J., Homs-Corbera A., Lechuga L.M. Journal of Biophotonics; 11 (8, e201800043) 2018. 10.1002/jbio.201800043. IF: 3.768

    Ultrasmooth gold/silver/gold trilayer nanostructured plasmonic sensors were obtained using commercial Blu-ray optical discs as nanoslits-based flexible polymer substrates. A thin gold film was used as an adhesion and nucleation layer to improve the chemical stability and reduce the surface roughness of the overlying silver film, without increasing ohmic plasmon losses. The structures were physically and optically characterized and compared with nanostructures of single gold layer. Ultrasmooth and chemically stable trilayer nanostructures with a surface roughness <0.5 nm were obtained following a simple and reproducible fabrication process. They showed a figure of merit (FOM) value up to 69.2 RIU−1 which is significantly higher (more than 95%) than the gold monolayer counterpart. Their potential for biosensing was demonstrated by employing the trilayer sensor for the direct and refractometric (label-free) detection of C-reactive protein (CRP) biomarker in undiluted urine achieving a Limit of Detection (LOD) in the pM order. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Interferometric nanoimmunosensor for label-free and real-time monitoring of Irgarol 1051 in seawater

    Chocarro-Ruiz B., Herranz S., Fernández Gavela A., Sanchís J., Farré M., Marco M.P., Lechuga L.M. Biosensors and Bioelectronics; 117: 47 - 52. 2018. 10.1016/j.bios.2018.05.044. IF: 8.173

    An interferometric nanobiosensor for the specific and label-free detection of the pollutant Irgarol 1051 directly in seawater has been settled. Due to the low molecular weight of Irgarol pollutant and its expected low concentration in seawater, the sensor is based on a competitive inhibition immunoassay. Parameters as surface biofunctionalization, concentration of the selective antibody and regeneration conditions have been carefully evaluated. The optimized immunosensor shows a limit of detection of only 3 ng/L, well below the 16 ng/L set by the EU as the maximum allowable concentration in seawater. It can properly operate during 30 assay-regeneration cycles using the same sensor biosurface and with a time-to-result of only 20 min for each cycle. Moreover, the interferometric nanosensor is able to directly detect low concentrations of Irgarol 1051 in seawater without requiring sample pre-treatments and without showing any background signal due to sea matrix effect. © 2018 Elsevier B.V.

  • Label-Free and Real-Time Detection of Tuberculosis in Human Urine Samples Using a Nanophotonic Point-of-Care Platform

    Ramirez-Priego P., Martens D., Elamin A.A., Soetaert P., Van Roy W., Vos R., Anton B., Bockstaele R., Becker H., Singh M., Bienstman P., Lechuga L.M. ACS Sensors; 3 (10): 2079 - 2086. 2018. 10.1021/acssensors.8b00393. IF: 5.711

    Tuberculosis (TB) is the leading global cause of death from a single infectious agent. Registered incidence rates are low, especially in low-resource countries with weak health systems, due to the disadvantages of current diagnostic techniques. A major effort is directed to develop a point-of-care (POC) platform to reduce TB deaths with a prompt and reliable low-cost technique. In the frame of the European POCKET Project, a novel POC platform for the direct and noninvasive detection of TB in human urine was developed. The photonic sensor chip is integrated in a disposable cartridge and is based on a highly sensitive Mach-Zehnder Interferometer (MZI) transducer combined with an on-chip spectral filter. The required elements for the readout are integrated in an instrument prototype, which allows real-time monitoring and data processing. In this work, the novel POC platform has been employed for the direct detection of lipoarabinomannan (LAM), a lipopolysaccharide found in the mycobacterium cell wall. After the optimization of several parameters, a limit of detection of 475 pg/mL (27.14 pM) was achieved using a direct immunoassay in undiluted human urine in less than 15 min. A final validation of the technique was performed using 20 clinical samples from TB patients and healthy donors, allowing the detection of TB in people regardless of HIV coinfection. The results show excellent correlation to those obtained with standard techniques. These promising results demonstrate the high sensitivity, specificity and applicability of our novel POC platform, which could be used during routine check-ups in developing countries. Copyright © 2018 American Chemical Society.

  • Label-free DNA-methylation detection by direct ds-DNA fragment screening using poly-purine hairpins

    Huertas C.S., Aviñó A., Kurachi C., Piqué A., Sandoval J., Eritja R., Esteller M., Lechuga L.M. Biosensors and Bioelectronics; 120: 47 - 54. 2018. 10.1016/j.bios.2018.08.027. IF: 8.173

    Cancer diagnosis continuously evolves due to the better understanding of tumorigenic processes. DNA-methylation is consolidated as an effective biomarker for cancer prognosis and diagnostic even in tumors of unknown origin. The reversibility of this epigenetic mechanism also places it as a high-profile tool for the development of more sophisticated and personalized therapies. Current methodologies, such as bisulfite conversion or PCR amplification, rely on complex procedures that make difficult the standardization of epigenetics analyses. Here we present an optical biosensor methodology based on Surface Plasmon Resonance that employs poly-purine reverse-Hoogsten hairpin probes capable of interacting directly with ds-DNA fragments by triple helix formation. The direct interaction with the material of interest can greatly enhance the reliability of the analysis providing a more accurate and precise diagnosis. We have demonstrated the capabilities of our methodology for the direct capture of ds-DNA fragments and specific methyl-cytosine quantification. Our poly-purine hairpin probe demonstrated the specific capture of ds-DNA fragments while the standard duplex-forming probes failed to do so. In addition, the biosensor methodology showed a strong correlation with the different DNA methylation status between the sequences with a low signal variation (≤ 8%CV) along 35 hybridization/regeneration cycles. Through its straightforward procedure and versatility of detecting different DNA modifications related to the DNA methylation process, we anticipate that our strategy will enable a greater level of accuracy and precision in cancer diagnostics making a strong impact on the development of personalized therapies. © 2018 Elsevier B.V.

  • Nanoplasmonic biosensor device for the monitoring of acenocoumarol therapeutic drug in plasma

    Peláez E.C., Estevez M.-C., Portela A., Salvador J.-P., Marco M.-P., Lechuga L.M. Biosensors and Bioelectronics; 119: 149 - 155. 2018. 10.1016/j.bios.2018.08.011. IF: 8.173

    Acenocoumarol (Sintrom®) is an oral anticoagulant prescribed for the treatment of a variety of thromboembolic disorders such as atrial fibrillation and thrombosis or embolism. It inhibits fibrin production preventing clot formation. Acenocoumarol has a narrow therapeutic range, and its effects depend on several factors, such as body weight, age, metabolism, diet, certain medical conditions or the intake of additional drugs, among others. A higher dose may result in the risk of bleeding, while if it is too low, the risk of blood clot can increase. Complementary tools that allow the therapeutic drug monitoring (TDM) of acenocoumarol plasmatic levels from the starting of the treatment would be of paramount importance to personalize the treatment. Point-of-care (POC) devices can offer an added value in facilitating on-site monitoring (i.e. hospitals, primary care doctor or even by the patient itself) and can aid in dosage management. With this aim, we have developed a compact and simple nanoplasmonic sensing device based on gold nanodisks for the rapid monitoring of acenocoumarol, using highly specific polyclonal antibodies produced against this drug. A specific and reproducible label free indirect competitive assay has been developed and the viability of performing the evaluation directly in plasma diluted 1:1 has been demonstrated. A limit of detection (LOD) of only 0.77 ± 0.69 nM, an IC50 of 48.2 ± 5.12 nM and a dynamic range between 3.38 ± 1.33 nM and 1154 ± 437 nM were achieved, which easily fit within the drug plasma levels of acenocoumarol, making this approach a highly attractive option for its decentralized monitoring in human plasma. © 2018 Elsevier B.V.


  • A label-free nanostructured plasmonic biosensor based on Blu-ray discs with integrated microfluidics for sensitive biodetection

    López-Muñoz G.A., Estevez M.-C., Peláez-Gutierrez E.C., Homs-Corbera A., García-Hernandez M.C., Imbaud J.I., Lechuga L.M. Biosensors and Bioelectronics; 96: 260 - 267. 2017. 10.1016/j.bios.2017.05.020. IF: 7.780

    Nanostructure-based plasmonic biosensors have quickly positioned themselves as interesting candidates for the design of portable optical biosensor platforms considering the potential benefits they can offer in integration, miniaturization, multiplexing, and real-time label-free detection. We have developed a simple integrated nanoplasmonic sensor taking advantage of the periodic nanostructured array of commercial Blu-ray discs. Sensors with two gold film thicknesses (50 and 100 nm) were fabricated and optically characterized by varying the oblique-angle of the incident light in optical reflectance measurements. Contrary to the use normal light incidence previously reported with other optical discs, we observed an enhancement in sensitivity and a narrowing of the resonant linewidths as the light incidence angle was increased, which could be related to the generation of Fano resonant modes. The new sensors achieve a figure of merit (FOM) up to 35 RIU−1 and a competitive bulk limit of detection (LOD) of 6.3×10−6 RIU. These values significantly improve previously reported results obtained with normal light incidence reflectance measurements using similar structures. The sensor has been combined with versatile, simple, ease to-fabricate microfluidics. The integrated chip is only 1 cm2 (including a PDMS flow cell with a 50 µm height microfluidic channel fabricated with double-sided adhesive tape) and all the optical components are mounted on a 10 cm×10 cm portable prototype, illustrating its facile miniaturization, integration and potential portability. Finally, to assess the label-free biosensing capability of the new sensor, we have evaluated the presence of specific antibodies against the GTF2b protein, a tumor-associate antigen (TAA) related to colorectal cancer. We have achieved a LOD in the pM order and have assessed the feasibility of directly measuring biological samples such as human serum. © 2017 Elsevier B.V.

  • An automated optofluidic biosensor platform combining interferometric sensors and injection moulded microfluidics

    Szydzik C., Gavela A.F., Herranz S., Roccisano J., Knoerzer M., Thurgood P., Khoshmanesh K., Mitchell A., Lechuga L.M. Lab on a Chip; 17 (16): 2793 - 2804. 2017. 10.1039/c7lc00524e. IF: 6.045

    A primary limitation preventing practical implementation of photonic biosensors within point-of-care platforms is their integration with fluidic automation subsystems. For most diagnostic applications, photonic biosensors require complex fluid handling protocols; this is especially prominent in the case of competitive immunoassays, commonly used for detection of low-concentration, low-molecular weight biomarkers. For this reason, complex automated microfluidic systems are needed to realise the full point-of-care potential of photonic biosensors. To fulfil this requirement, we propose an on-chip valve-based microfluidic automation module, capable of automating such complex fluid handling. This module is realised through application of a PDMS injection moulding fabrication technique, recently described in our previous work, which enables practical fabrication of normally closed pneumatically actuated elastomeric valves. In this work, these valves are configured to achieve multiplexed reagent addressing for an on-chip diaphragm pump, providing the sample and reagent processing capabilities required for automation of cyclic competitive immunoassays. Application of this technique simplifies fabrication and introduces the potential for mass production, bringing point-of-care integration of complex automated microfluidics into the realm of practicality. This module is integrated with a highly sensitive, label-free bimodal waveguide photonic biosensor, and is demonstrated in the context of a proof-of-concept biosensing assay, detecting the low-molecular weight antibiotic tetracycline. © 2017 The Royal Society of Chemistry.

  • Analysis of alternative splicing events for cancer diagnosis using a multiplexing nanophotonic biosensor

    Huertas C.S., Domínguez-Zotes S., Lechuga L.M. Scientific Reports; 7 ( 41368) 2017. 10.1038/srep41368. IF: 4.259

    Personalized medicine is a promising tool not only for prevention, screening and development of more efficient treatment strategies, but also for diminishing the side effects caused by current therapies. Deciphering gene regulation pathways provides a reliable prognostic analysis to elucidate the origin of grave diseases and facilitate the selection of the most adequate treatment for each individual. Alternative splicing of mRNA precursors is one of these gene regulation pathways and enables cells to generate different protein outputs from the same gene depending on their developmental or homeostatic status. Its deregulation is strongly linked to disease onset and progression constituting a relevant and innovative class of biomarker. Herein we report a highly selective and sensitive nanophotonic biosensor based on the direct monitoring of the aberrant alternative splicing of Fas gene. Unlike conventional methods, the nanobiosensor performs a real-time detection of the specific isoforms in the fM-pM range without any cDNA synthesis or PCR amplification requirements. The nanobiosensor has been proven isoform-specific with no crosshybridization, greatly minimizing detection biases. The demonstrated high sensitivity and specificity make our nanobiosensor ideal for examining significant tumor-associated expression shifts of alternatively spliced isoforms for the early and accurate theranostics of cancer.

  • Array of Microfluidic Beam Resonators for Density and Viscosity Analysis of Liquids

    Marquez S., Álvarez M., Fariña Santana D., Homs-Corbera A., Domínguez C., Lechuga L.M. Journal of Microelectromechanical Systems; 26 (4, 7945266): 749 - 757. 2017. 10.1109/JMEMS.2017.2709944. IF: 2.124

    This paper reports on the design, fabrication, and evaluation of a mass density and viscosity sensor based on an array of polysilicon microbeam resonators integrated with 20 pL fluidic microchannels. When filled with water, resonators exhibit resonant frequencies close to 500 KHz and Q-factor values of 400 operating at atmospheric pressure and ambient temperature. Real-time measurements are highly reproducible and only require 250 μL of the sample fluid. The built-in interferometric readout enables automatic detection of the beams increasing the throughput analysis and reducing detection times. The frequency shift response shows a linear behavior in accordance with the density of evaluated solvents, organic solutions, and alcoholic drinks, reporting a mass responsivity of 7.4 Hz/pg. Also, the sensor is capable of measuring the viscosity of liquid phase samples with a resolution of 0.15 cP by tracking the Q-factor response of the sensor within a linear regime between 1 to 2.6 cP. This approach demonstrates the ability to identify in real-time changes of fluids in the liquid phase that could provide a valuable assessment for bioanalytical applications. © 2017 IEEE.

  • Asymmetrically coupled resonators for mass sensing

    Marquez S., Alvarez M., Plaza J.A., Villanueva L.G., Dominguez C., Lechuga L.M. Applied Physics Letters; 111 (11, 113101) 2017. 10.1063/1.5003023. IF: 3.411

    Mechanically coupled resonators have been applied in the last years to the development of nanomechanical mass-sensors based on the detection of the different vibration modes of the system by measuring on a single resonator. Their sensitivity and capability for detecting multiple analytes strongly depends on the design and coupling strength between the mechanically coupled resonators in an array format. We present a theoretical and experimental study of the behavior of an asymmetrically coupled array of four different resonators. These doubly clamped beam resonators are elastically coupled by an overhang region of varying length along the transversal axis of the array. The results show that parameters such as the gap between microbeams and the overhang length affect the coupling strength, tuning the system from highly disordered and highly localized (weak coupling) to highly delocalized (strong coupling). In the strong coupling and partially localized case, the distances between resonant peaks are larger, reaching higher eigenfrequency values. In this case, relative changes in a specific eigenstate, due to an added mass, can be markedly large due to the energy distribution over a single microbeam. A strong coupling also facilitates performing the detection on the relative frequency shift mode, which can usually be resolved with better precision than the amplitude changes. © 2017 Author(s).

  • Cryptophane-cladded interferometric waveguide sensor for aqueous methane detection

    Jágerská J., Dullo F.T., Lindecrantz S.M., Börgers J.M., Hansen J.H., Lechuga L.M., Hellesø O.G. Optics InfoBase Conference Papers; Part F43-CLEO_AT 2017 2017. 10.1364/CLEO_AT.2017.AM3B.4. IF: 0.000

    A nanophotonic sensor for sensitive detection of methane in water solution is presented. Cryptophane-A doped waveguide cladding provides for methane pre-concentration on a chip, resulting in a detection limit of 60 ppm (86 nM). © 2017 OSA.

  • Direct and label-free detection of the human growth hormone in urine by an ultrasensitive bimodal waveguide biosensor

    González-Guerrero A.B., Maldonado J., Dante S., Grajales D., Lechuga L.M. Journal of Biophotonics; 10 (1): 61 - 67. 2017. 10.1002/jbio.201600154. IF: 4.328

    A label-free interferometric transducer showing a theoretical detection limit for homogeneous sensing of 5 × 10–8 RIU, being equivalent to a protein mass coverage resolution of 2.8 fg mm–2, is used to develop a high sensitive biosensor for protein detection. The extreme sensitivity of this transducer combined with a selective bioreceptor layer enables the direct evaluation of the human growth hormone (hGH) in undiluted urine matrix in the 10 pg mL–1 range. (Figure presented.). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Label-free biosensors based on bimodal waveguide (BiMW) interferometers

    Herranz S., Gavela A.F., Lechuga L.M. Methods in Molecular Biology; 1571: 161 - 185. 2017. 10.1007/978-1-4939-6848-0_11.

    The bimodal waveguide (BiMW) sensor is a novel common path interferometric transducer based on the evanescent field detection principle, which in combination with a bio-recognition element allows the direct detection of biomolecular interactions in a label-free scheme. Due to its inherent high sensitivity it has great potential to become a powerful analytical tool for monitoring substances of interest in areas such as environmental control, medical diagnostics and food safety, among others. The BiMW sensor is fabricated using standard silicon-based technology allowing cost-effective production, and meeting the requirements of portability and disposability necessary for implementation in a point-of-care (POC) setting. In this chapter we describe the design and fabrication of the BiMW transducer, as well as its application for bio-sensing purposes. We show as an example the biosensor capabilities two different applications: (1) the immunodetection of Irgarol 1051 biocide useful in the environmental field, and (2) the detection of human growth hormone as used in clinical diagnostics. The detection is performed in real time by monitoring changes in the intensity pattern of light exiting the BiMW transducer resulting from antigen–antibody interactions on the surface of the sensor. © Springer Science+Business Media LLC 2017.

  • Nanophotonic interferometric immunosensors for label-free and real-time monitoring of chemical contaminants in marine environment

    Chocarro-Ruiz B., Herranz S., Fernández Gavela A., Lechuga L.M. Proceedings of SPIE - The International Society for Optical Engineering; 10215 ( 1021503) 2017. 10.1117/12.2256982. IF: 0.000

    With the aim to prevent the oceans ecosystems degradation, there is an urgent need to develop portable sensing tools able to operate directly in the environment, avoiding the transportation of the ocean samples to analytical laboratories. To achieve this long-term objective, we describe here the work carried out to develop and characterize a multiplexed photonic immunosensor for the direct analysis of toxic chemical targets in marine samples. We have employed immunosensors based on photonic Bimodal Waveguide (BiMW) interferometric devices fabricated in silicon technologies combined with specific receptors and antibodies for the targeted chemical targets. Several procedures for the functionalization of the Si3N4 sensor surfaces have been evaluated based on wet silanization methods and further covalent receptor immobilization. The developed immunosensors, based on competitive inhibition assays, show LODs at μg/L or ng/L levels, depending on the analyzed chemical target. © 2017 SPIE.

  • Nanophotonic label-free biosensors for environmental monitoring

    Chocarro-Ruiz B., Fernández-Gavela A., Herranz S., Lechuga L.M. Current Opinion in Biotechnology; 45: 175 - 183. 2017. 10.1016/j.copbio.2017.03.016. IF: 9.294

    The field of environmental monitoring has experienced a substantial progress in the last years but still the on-site control of contaminants is an elusive problem. In addition, the growing number of pollutant sources is accompanied by an increasing need of having efficient early warning systems. Several years ago biosensor devices emerged as promising environmental monitoring tools, but their level of miniaturization and their fully operation outside the laboratory prevented their use on-site. In the last period, nanophotonic biosensors based on evanescent sensing have emerged as an outstanding choice for portable point-of-care diagnosis thanks to their capability, among others, of miniaturization, multiplexing, label-free detection and integration in lab-on-chip platforms. This review covers the most relevant nanophotonic biosensors which have been proposed (including interferometric waveguides, grating-couplers, microcavity resonators, photonic crystals and localized surface plasmon resonance sensors) and their recent application for environmental surveillance. © 2017 Elsevier Ltd

  • Preface – European Materials Research Society (E-MRS) Spring Meeting 2016 Symposium M: Silicon compatible materials and integrated devices for photonics and optical sensing

    Miritello M., Rebohle L., Lechuga L.M., Maier S. Journal of Luminescence; 191: 87. 2017. 10.1016/j.jlumin.2017.07.001.

    [No abstract available]

  • Recent advances in nanoplasmonic biosensors: Applications and lab-on-a-chip integration

    Lopez G.A., Estevez M.-C., Soler M., Lechuga L.M. Nanophotonics; 6 (1): 123 - 136. 2017. 10.1515/nanoph-2016-0101. IF: 4.492

    Motivated by the recent progress in the nanofabrication field and the increasing demand for cost-effective, portable, and easy-to-use point-of-care platforms, localized surface plasmon resonance (LSPR) biosensors have been subjected to a great scientific interest in the last few years. The progress observed in the research of this nanoplasmonic technology is remarkable not only from a nanostructure fabrication point of view but also in the complete development and integration of operative devices and their application. The potential benefits that LSPR biosensors can offer, such as sensor miniaturization, multiplexing opportunities, and enhanced performances, have quickly positioned them as an interesting candidate in the design of lab-on-a-chip (LOC) optical biosensor platforms. This review covers specifically the most significant achievements that occurred in recent years towards the integration of this technology in compact devices, with views of obtaining LOC devices. We also discuss the most relevant examples of the use of the nanoplasmonic biosensors for real bioanalytical and clinical applications from assay development and validation to the identification of the implications, requirements, and challenges to be surpassed to achieve fully operative devices. © 2016, Laura M. Lechuga et al., published by De Gruyter.

  • Simple, low-cost and timely optical biosensors for the detection of epigenetics biomarkers: the future of cancer diagnosis

    C. S. Huertas and L. M. Lechuga European Medical Journal; 5 (1): 54 - 61. 2017. .

    The cancer burden continues to grow with enormous physical, emotional, and financial pressure on individuals, families, communities, and health systems. Early detection and effective treatment are crucial. The analysis of epigenetic biomarkers is presented as an exceptional solution for early cancer diagnosis and personalised treatment design. These brand new biomarkers have initiated a diagnostic revolution because of their predictive capability and reversibility, opening the window for timely diagnostics and personalised medicine. In recent years, the potential of optical biosensors for epigenetic biomarker evaluation has been revealed. Nanotechnology is promoting the appearance of new advanced biosensors able to be integrated in complete lab-on-chip platforms. Lab-on-chip biosensors are offering simplified, cost-effective, and fast results to solve the current diagnostic problems. In this review, we present the advantages offered by the analysis of epigenetic routes in cancer diagnosis and the current advances in optical biosensors for cancer epigenetic analysis, showing how the new biosensor solutions manage to surpass the challenges encountered during the analysis of each epigenetic mechanism.

  • Species-specific modulation of food-search behavior by respiration and chemosensation in Drosophila larvae

    Kim D., Alvarez M., Lechuga L.M., Louis M. eLife; 6 ( e27057) 2017. 10.7554/eLife.27057. IF: 7.725

    Animals explore their environment to encounter suitable food resources. Despite its vital importance, this behavior puts individuals at risk by consuming limited internal energy during locomotion. We have developed a novel assay to investigate how food-search behavior is organized in Drosophila melanogaster larvae dwelling in hydrogels mimicking their natural habitat. We define three main behavioral modes: resting at the gel’s surface, digging while feeding near the surface, and apneic dives. In unstimulated conditions, larvae spend most of their time digging. By contrast, deep and long exploratory dives are promoted by olfactory stimulations. Hypoxia and chemical repellents impair diving. We report remarkable differences in the dig-and-dive behavior of D. melanogaster and the fruit-pest D. suzukii. The present paradigm offers an opportunity to study how sensory and physiological cues are integrated to balance the limitations of dwelling in imperfect environmental conditions and the risks associated with searching for potentially more favorable conditions. © Kim et al.

  • The potential of nanophotonic lab-on-chip biosensors for high-value diagnostics

    Lechuga L.M. Optics InfoBase Conference Papers; Part F82-CLEO_Europe 2017 2017. .

    [No abstract available]

  • Vertical adiabatic taper for efficient in-coupling in nano-interferometric waveguide biosensors

    Grajales D., Gavela A.F., Domi´nguez C., Lechuga L.M. Optics InfoBase Conference Papers; Part F82-CLEO_Europe 2017 2017. .

    [No abstract available]


  • Fabrication of well-ordered silicon nanopillars embedded in a microchannel: Via metal-assisted chemical etching: A route towards an opto-mechanical biosensor

    Solis-Tinoco V., Marquez S., Sepulveda B., Lechuga L.M. RSC Advances; 6 (88): 85666 - 85674. 2016. 10.1039/c6ra15485a. IF: 3.289

    Ordered nanopillars have been used as a smart configuration to design and fabricate localized surface plasmon resonance (LSPR) sensors. Importantly, these nanostructures can be integrated within microfluidic channels as a novel opportunity to enhance the response of biosensors and also to control the fluid flow by modifying the wettability surface of the walls. In this work, we demonstrate a large-scale and low-cost nanofabrication methodology that integrates the fabrication of silicon nanopillars (SiNPs) inside a microfluidic channel. The strategy is based on placing a catalytic gold layer patterned with nanoholes inside a SU-8 microchannel, by combining nanosphere lithography, reactive ion etching, and e-beam gold deposition, to control the area, separation distance and diameter of the nanostructures. The height of the SiNPs strongly depends on a well-controlled metal-assisted silicon etching protocol. We demonstrate experimentally that the design and the cleaning of the catalytic gold mesh using ultraviolet ozone strongly affect the etching rate for the formation of large-surface-area nanopillars. Our results explain the fast fabrication of hexagonal arrays of SiNPs embedded in a microfluidic channel with varying aspect ratio from 2 to 7 and separation of 300 nm and 400 nm, respectively, which has important implications for the achievement of new optomechanical biosensors. © The Royal Society of Chemistry 2016.

  • Label-free bimodal waveguide immunosensor for rapid diagnosis of bacterial infections in cirrhotic patients

    Maldonado J., González-Guerrero A.B., Domínguez C., Lechuga L.M. Biosensors and Bioelectronics; 85: 310 - 316. 2016. 10.1016/j.bios.2016.04.095. IF: 7.476

    Spontaneous bacterial peritonitis is an acute bacterial infection of ascitic fluid; it has a high incidence in cirrhotic patients and it is associated with high mortality. In such a situation, early diagnosis and treatment is crucial for the survival of the patient. However, bacterial analysis in ascitic fluid is currently based on culture methods, which are time-consuming and laborious. We report here the application of a photonic interferometer biosensor based on a bimodal waveguide (BiMW) for the rapid and label-free detection of bacteria directly in ascitic fluid. The device consists of a straight waveguide in which two modes of the same polarization interfere while interacting with the external medium through their evanescent fields. A bimolecular event occurring on the sensor area of the device (e.g. capturing bacteria) will differently affect each light mode, inducing a variation in the phase of the light exiting at the output of the waveguide. In this work, we demonstrate the quantitative detection of Bacillus cereus in buffer medium and Escherichia coli in undiluted ascitic fluid from cirrhotic patients. In the case of Bacillus cereus detection, the device was able to specifically detect bacteria at relevant concentrations in 12.5 min and in the case of Escherichia coli detection, the analysis time was 25 min. Extrapolation of the data demonstrated that the detection limits of the biosensor could reach few bacteria per milliliter. Based on the results obtained, we consider that the BiMW biosensor is positioned as a promising new clinical tool for user-friendly, cost-effective and real-time microbiological analysis. © 2016 Elsevier B.V.

  • Label-free nanoplasmonic sensing of tumor-associate autoantibodies for early diagnosis of colorectal cancer

    Soler M., Estevez M.-C., Villar-Vazquez R., Casal J.I., Lechuga L.M. Analytica Chimica Acta; 930: 31 - 38. 2016. 10.1016/j.aca.2016.04.059. IF: 4.712

    Colorectal cancer is treatable and curable when detected at early stages. However there is a lack of less invasive and more specific screening and diagnosis methods which would facilitate its prompt identification. Blood circulating autoantibodies which are immediately produced by the immune system at tumor appearance have become valuable biomarkers for preclinical diagnosis of cancer. In this work, we present the rapid and label-free detection of colorectal cancer autoantibodies directly in blood serum or plasma using a recently developed nanoplasmonic biosensor. Our nanoplasmonic device offers sensitive and real-time quantification of autoantibodies with excellent selectivity and reproducibility, achieving limits of detection around 1 nM (150-160 ng mL-1). A preliminary evaluation of clinical samples of colorectal cancer patients has shown good correlation with ELISA. These results demonstrate the reliability of the nanobiosensor strategy and pave the way towards the achievement of a sensitive diagnostic tool for early detection of colorectal cancer. © 2016 Elsevier B.V.

  • Label-free SPR detection of gluten peptides in urine for non-invasive celiac disease follow-up

    Soler M., Estevez M.-C., Moreno M.D.L., Cebolla A., Lechuga L.M. Biosensors and Bioelectronics; 79: 158 - 164. 2016. 10.1016/j.bios.2015.11.097. IF: 7.476

    Motivated by the necessity of new and efficient methods for dietary gluten control of celiac patients, we have developed a simple and highly sensitive SPR biosensor for the detection of gluten peptides in urine. The sensing methodology enables rapid and label-free quantification of the gluten immunogenic peptides (GIP) by using G12 mAb. The overall performance of the biosensor has been in-depth optimized and evaluated in terms of sensitivity, selectivity and reproducibility, reaching a limit of detection of 0.33ngmL-1. Besides, the robustness and stability of the methodology permit the continuous use of the biosensor for more than 100 cycles with excellent repeatability. Special efforts have been focused on preventing and minimizing possible interferences coming from urine matrix enabling a direct analysis in this fluid without requiring extraction or purification procedures. Our SPR biosensor has proven to detect and identify gluten consumption by evaluating urine samples from healthy and celiac individuals with different dietary gluten conditions. This novel biosensor methodology represents a novel approach to quantify the digested gluten peptides in human urine with outstanding sensitivity in a rapid and non-invasive manner. Our technique should be considered as a promising opportunity to develop Point-of-Care (POC) devices for an efficient, simple and accurate gluten free diet (GFD) monitoring as well as therapy follow-up of celiac disease patients. © 2015 Elsevier B.V.

  • Last advances in silicon-based optical biosensors

    Gavela A.F., García D.G., Ramirez J.C., Lechuga L.M. Sensors (Switzerland); 16 (3, 285) 2016. 10.3390/s16030285. IF: 2.033

    We review the most important achievements published in the last five years in the field of silicon-based optical biosensors. We focus specially on label-free optical biosensors and their implementation into lab-on-a-chip platforms, with an emphasis on developments demonstrating the capability of the devices for real bioanalytical applications. We report on novel transducers and materials, improvements of existing transducers, new and improved biofunctionalization procedures as well as the prospects for near future commercialization of these technologies. © 2016 by the authors; licensee MDPI, Basel, Switzerland.

  • Out-of-plane single-mode photonic microcantilevers for integrated nanomechanical sensing platform

    Fariña Santana D., Álvarez M., Márquez S., Domínguez C., Lechuga L.M. Sensors and Actuators, B: Chemical; 232: 60 - 67. 2016. 10.1016/j.snb.2016.03.041. IF: 4.758

    We have studied the optomechanical performance of optical microcantilevers fabricated with integrated waveguides for the on-chip and real-time detection of biorecognition events. The nanomechanical photonic device consists of an optical microcantilever with on-chip integrated waveguides for both coupling the light and detecting the microcantilever response. The photonic device was designed to reach a high sensitivity with a low deflection noise density (DND) of only 0.13fm/√ Hz. The BioMEMS transducer is embedded into a proper designed PMMA/PDMS microfluidic header and connected to a flow delivery system to study the response of the fully-integrated device under physiological conditions. As a proof of concept, we have studied the photonic microcantilever bending during consecutive formation of ultrathin polyelectrolyte multilayer films (electrostatic binding) and during biofunctionalization and biorecognition of the human growth hormone. The read-out platform was developed based on a single laser-single acquisition channel. To avoid the effect of external factors such as device positioning or temperature fluctuations, an automatized light coupling system keeps on tracking the laser beam focused into an input waveguide, increasing the required reproducibility needed for BioMEMS devices and paving the way for a potential portable multichannel sensor platform. © 2016 Elsevier B.V. All rights reserved.

  • Prospects of optical biosensors for emerging label-free RNA analysis

    Carrascosa L.G., Huertas C.S., Lechuga L.M. TrAC - Trends in Analytical Chemistry; 80: 177 - 189. 2016. 10.1016/j.trac.2016.02.018. IF: 7.487

    RNA is critical in countless cellular processes, and researchers are constantly discovering new types and attributing them different roles. Consequently, a growing interest in efficient RNA analysis has arisen. However, RNA detection is complicated and generally requires the use of labels. Major efforts are being devoted to conceive new approaches for RNA analysis with no need of markers. Optical biosensing is a highly sensitive approach that circumvents many of conventional methods' limitations. Lately, label-free applications with optical biosensors have been developed for short as well as for long RNAs. The low limits of detection at the pM level enabled by optical biosensors, together with a fast analysis, their reusability and the label-free scheme of operation, clearly highlight them among the most promising next-generation RNA screening platforms. This review covers the most relevant optical biosensor platforms and their potential for enabling sensitive and label-free RNA analysis. © 2016 Elsevier B.V.

  • Quantitative evaluation of alternatively spliced mRNA isoforms by label-free real-time plasmonic sensing

    Huertas C.S., Carrascosa L.G., Bonnal S., Valcárcel J., Lechuga L.M. Biosensors and Bioelectronics; 78: 118 - 125. 2016. 10.1016/j.bios.2015.11.023. IF: 7.476

    Alternative splicing of mRNA precursors enables cells to generate different protein outputs from the same gene depending on their developmental or homeostatic status. Its deregulation is strongly linked to disease onset and progression. Current methodologies for monitoring alternative splicing demand elaborate procedures and often present difficulties in discerning between closely related isoforms, e.g. due to cross-hybridization during their detection. Herein, we report a general methodology using a Surface Plasmon Resonance (SPR) biosensor for label-free monitoring of alternative splicing events in real-time, without any cDNA synthesis or PCR amplification requirements. We applied this methodology to RNA isolated from HeLa cells for the quantification of alternatively spliced isoforms of the Fas gene, involved in cancer progression through regulation of programmed cell death. We demonstrate that our methodology is isoform-specific, with virtually no cross-hybridization, achieving limits of detection (LODs) in the picoMolar (pM) range. Similar results were obtained for the detection of the BCL-X gene mRNA isoforms. The results were independently validated by RT-qPCR, with excellent concordance in the determination of isoform ratios. The simplicity and robustness of this biosensor technology can greatly facilitate the exploration of alternative splicing biomarkers in disease diagnosis and therapy. © 2015 Elsevier B.V.

  • Sensitive and label-free detection of miRNA-145 by triplex formation

    Aviñó A., Huertas C.S., Lechuga L.M., Eritja R. Analytical and Bioanalytical Chemistry; 408 (3): 885 - 893. 2016. 10.1007/s00216-015-9180-6. IF: 3.125

    The development of new strategies for detecting microRNAs (miRNAs) has become a crucial step in the diagnostic field. miRNA profiles depend greatly on the sample and the analytical platform employed, leading sometimes to contradictory results. In this work, we study the use of modified parallel tail-clamps to detect a miRNA sequence involved in tumor suppression by triplex formation. Thermal denaturing curves and circular dichroism (CD) measurements have been performed to confirm that parallel clamps carrying 8-aminoguanine form the most stable triplex structures with their target miRNA. The modified tail-clamps have been tested as bioreceptors in a surface plasmon resonance (SPR) biosensor for the detection of miRNA-145. The detection limit was improved 2.4 times demonstrating that a stable triplex structure is formed between target miRNA and 8-aminoguanine tail-clamp bioreceptor. This new approach is an essential step toward the label-free and reliable detection of miRNA signatures for diagnostic purposes. © 2015 Springer-Verlag Berlin Heidelberg.

  • Towards an integrated optofluidic system for highly sensitive detection of antibiotics in seawater incorporating bimodal waveguide photonic biosensors and complex, active microfluidics

    Szydzik C., Gavela A.F., Roccisano J., Herranz De Andrés S., Mitchell A., Lechuga L.M. Proceedings of SPIE - The International Society for Optical Engineering; 10013 (100132C) 2016. 10.1117/12.2242885.

    We present recent results on the realisation and demonstration of an integrated optofluidic lab-on-a-chip measurement system. The system consists of an integrated on-chip automated microfluidic fluid handling subsystem, coupled with bimodal nano-interferometer waveguide technology, and is applied in the context of detection of antibiotics in seawater. The bimodal waveguide (BMWG) is a highly sensitive label-free biosensor. Integration of complex microfluidic systems with bimodal waveguide technology enables on-chip sample handling and fluid processing capabilities and allows for significant automation of experimental processes. The on-chip fluid-handling subsystem is realised through the integration of pneumatically actuated elastomer pumps and valves, enabling high temporal resolution sample and reagent delivery and facilitating multiplexed detection processes. © 2016 SPIE.

  • Towards the design of universal immunosurfaces for SPR-based assays: A review

    Mauriz E., García-Fernández M.C., Lechuga L.M. TrAC - Trends in Analytical Chemistry; 79: 191 - 198. 2016. 10.1016/j.trac.2016.02.006. IF: 7.487

    Surface biofunctionalization, including chemical activation and attachment of the bioreceptor, is an essential step to provide reliable detection of biomolecular binding events monitored by Surface Plasmon Resonance (SPR), the most employed optical biosensor, and other biosensor techniques. Recent progress in the area of immobilization procedures are aimed at producing reproducible interfacial surfaces that enable the sensitive and specific recognition of the analyte. Antibodies are still the most employed bioreceptors for SPR assays. A wide range of strategies have been proposed to maximize the SPR immunosensor performance by controlling the stability and orientation of the immobilized antibody. This article reviews the most recent advancements in random and oriented antibody immobilization approaches for SPR biosensing applications, with a special focus on the research that have been done to find universal linkers, which can allow the use of the same functionalized surface for different applications. © 2016.

  • Trends in photonic lab-on-chip interferometric biosensors for point-of-care diagnostics

    González-Guerrero A.B., Maldonado J., Herranz S., Lechuga L.M. Analytical Methods; 8 (48): 8380 - 8394. 2016. 10.1039/c6ay02972h. IF: 1.915

    Portable point-of care (POC) devices for in vitro diagnostics will be a milestone for the achievement of universal healthcare and environmental protection. The main goal is to reach a rapid, user-friendly and highly sensitive portable tool which can provide immediate results in any place at any time while having a competitive cost. Integrated optical (IO) waveguide based-biosensors are the most suitable candidates to achieve this ambitious objective. They are able to operate in real samples (such as blood, urine, wastewater…) affording relevant sensitivities even under a label-free scheme. In addition, arrays of IO sensors for multiplexed analysis can be integrated in lab-on-chip (LOC) platforms, providing a truly cost-effective fabrication and miniaturization. Among the different IO biosensors, interferometric ones have demonstrated the highest sensitivity for label-free detection ever reported. Although the first interferometric biosensors were developed in the early nineties, they focused mainly on preliminary proof-of-concept studies; only recently the resilient potential of interferometric biosensors as highly advanced POC devices has firmly emerged. This review provides an overview of the state-of-the art in photonic interferometric biosensors, their main biofunctionalisation routes and their integration in LOC platforms, while maintaining a special focus on the real analytical applications achieved so far. © The Royal Society of Chemistry.


  • Design of a surface plasmon resonance immunoassay for therapeutic drug monitoring of amikacin

    Losoya-Leal A., Estevez M.-C., Martínez-Chapa S.O., Lechuga L.M. Talanta; 141: 253 - 258. 2015. 10.1016/j.talanta.2015.04.009. IF: 3.545

    The therapeutic drug monitoring (TDM) of pharmaceutical drugs with narrow therapeutic ranges is of great importance in the clinical setting. It provides useful information towards the enhancement of drug therapies, aiding in dosage control and toxicity risk management. Amikacin is an aminoglycoside antibiotic commonly used in neonatal therapies that is indicated for TDM due to the toxicity risks inherent in its use. Current techniques for TDM such as high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) are costly, time consuming, and cannot be performed at the site of action. Over the last decades, surface plasmon resonance (SPR) biosensors have become increasingly popular in clinical diagnostics due to their ability to detect biomolecular interactions in real-time. We present an SPR-based competitive immunoassay for the detection of the antibiotic amikacin, suitable for TDM in both adults and neonates. We have obtained high specificity and sensitivity levels with an IC50 value of 1.4 ng/mL and a limit of detection of 0.13 ng/mL, which comfortably comply with the drug's therapeutic range. Simple dilution of serum can therefore be sufficient to analyze low-volume real samples from neonates, increasing the potential of the methodology for TDM. Compared to current TDM conventional methods, this SPR-based immunoassay can provide advantages such as simplicity, potential portability, and label-free measurements with the possibility of high throughput. This work is the foundation towards the development of an integrated, simple use, highly sensitive, fast, and point-of-care sensing platform for the opportune TDM of antibiotics and other drugs in a clinical setting. © 2015 Elsevier B.V. All rights reserved.

  • Highly sensitive dendrimer-based nanoplasmonic biosensor for drug allergy diagnosis

    Soler M., Mesa-Antunez P., Estevez M.-C., Ruiz-Sanchez A.J., Otte M.A., Sepulveda B., Collado D., Mayorga C., Torres M.J., Perez-Inestrosa E., Lechuga L.M. Biosensors and Bioelectronics; 66: 115 - 123. 2015. 10.1016/j.bios.2014.10.081. IF: 6.409

    A label-free biosensing strategy for amoxicillin (AX) allergy diagnosis based on the combination of novel dendrimer-based conjugates and a recently developed nanoplasmonic sensor technology is reported. Gold nanodisks were functionalized with a custom-designed thiol-ending-polyamido-based dendron (d-BAPAD) peripherally decorated with amoxicilloyl (AXO) groups (d-BAPAD-AXO) in order to detect specific IgE generated in patient's serum against this antibiotic during an allergy outbreak. This innovative strategy, which follows a simple one-step immobilization procedure, shows exceptional results in terms of sensitivity and robustness, leading to a highly-reproducible and long-term stable surface which allows achieving extremely low limits of detection. Moreover, the viability of this biosensor approach to analyze human biological samples has been demonstrated by directly analyzing and quantifying specific anti-AX antibodies in patient's serum without any sample pretreatment. An excellent limit of detection (LoD) of 0.6. ng/mL (i.e. 0.25. kU/L) has been achieved in the evaluation of clinical samples evidencing the potential of our nanoplasmonic biosensor as an advanced diagnostic tool to quickly identify allergic patients. The results have been compared and validated with a conventional clinical immunofluorescence assay (ImmunoCAP test), confirming an excellent correlation between both techniques. The combination of a novel compact nanoplasmonic platform and a dendrimer-based strategy provides a highly sensitive label free biosensor approach with over two times better detectability than conventional SPR. Both the biosensor device and the carrier structure hold great potential in clinical diagnosis for biomarker analysis in whole serum samples and other human biological samples. © 2014 Elsevier B.V.

  • Linear readout of integrated interferometric biosensors using a periodic wavelength modulation

    Dante S., Duval D., Fariña D., González-Guerrero A.B., Lechuga L.M. Laser and Photonics Reviews; 9 (2): 248 - 255. 2015. 10.1002/lpor.201400216. IF: 8.008

    An all-optical phase modulation method for the linear readout of integrated interferometric biosensors is demonstrated, merging simple intensity detection with the advantages offered by spectral interrogation. The phase modulation is introduced in a simple and cost-effective way by tuning a few nanometers the emission wavelength of commercial laser diodes, taking advantage of their well-known drawback of power-wavelength dependence. The method is applied to the case of a bimodal waveguide (BiMW) interferometric biosensor, fabricated with standard silicon technology and operated at visible wavelengths, rendering a detection limit of 4×10-7 refractive index units for bulk sensing. The biosensing capabilities of the phase-linearized BiMW device are assessed through the quantitative immunoassay of C-reactive protein, a key protein in inflammatory processes. This method can be applied to any modal interferometer. To solve the ambiguities affecting interferometric biosensors, a phase modulation system based on variations of the incident wavelength and Fourier deconvolution is presented. The wavelength variation is introduced taking advantage of the power-wavelength dependence of commercial laser diodes, resulting in a cost-effective method, valid for all modal interferometers. Considering the modulation of a bimodal waveguide interferometric sensor, limits of detection of 4 · 10-7 for bulk sensing and 7 ng/ml for the detection of C-Reactive protein were demonstrated. © 2015 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • Novel nanoplasmonic biosensor integrated in a microfluidic channel

    Solis-Tinoco V., Sepulveda B., Lechuga L.M. Proceedings of SPIE - The International Society for Optical Engineering; 9519 ( 95190T) 2015. 10.1117/12.2178990. IF: 0.000

    An important motivation of the actual biosensor research is to develop a multiplexed sensing platform of high sensitivity fabricated with large-scale and low-cost technologies for applications such as diagnosis and monitoring of diseases, drug discovery and environmental control. Biosensors based on localized plasmon resonance (LSPR) have demonstrated to be a novel and effective platform for quantitative detection of biological and chemical analytes. Here, we describe a novel label-free nanobiosensor consisting of an array of closely spaced, vertical, elastomeric nanopillars capped with plasmonic gold nanodisks in a SU-8 channel. The principle is based on the refractive index sensing using the LSPR of gold nanodisks. The fabrication of the nanobiosensor is based on replica molding technique and gold nanodisks are incorporated on the polymer structures by e-beam evaporation. In this work, we provide the strategies for controlling the silicon nanostructure replication using thermal polymers and photopolymers with different Young's modulus, in order to minimize the common distortions in the process and to obtain a reliable replica of the Si master. The master mold of the biosensor consists of a hexagonal array of silicon nanopillars, whose diameter is ∼200 nm, and whose height can range from 250 nm to 1.300 μm, separated 400 nm from the center to center, integrated in a SU-8 microfluidic channel. © 2015 SPIE.

  • Numerical study of a high sensitive polymer biosensor using a trimodal waveguide interferometer

    Ramirez J.C., Lechuga L.M., Gabrielli L.H., Hernandez-Figueroa H.E. Proceedings 2015 European Conference on Lasers and Electro-Optics - European Quantum Electronics Conf; 2015. . IF: 0.000

    [No abstract available]

  • Sensitivity analysis for improving nanomechanical photonic transducers biosensors

    Fariña D., Álvarez M., Márquez S., Dominguez C., Lechuga L.M. Journal of Physics D: Applied Physics; 48 (33, 335401) 2015. 10.1088/0022-3727/48/33/335401. IF: 2.721

    The achievement of high sensitivity and highly integrated transducers is one of the main challenges in the development of high-throughput biosensors. The aim of this study is to improve the final sensitivity of an opto-mechanical device to be used as a reliable biosensor. We report the analysis of the mechanical and optical properties of optical waveguide microcantilever transducers, and their dependency on device design and dimensions. The selected layout (geometry) based on two butt-coupled misaligned waveguides displays better sensitivities than an aligned one. With this configuration, we find that an optimal microcantilever thickness range between 150 nm and 400 nm would increase both microcantilever bending during the biorecognition process and increase optical sensitivity to 4.8 × 10-2 nm-1, an order of magnitude higher than other similar opto-mechanical devices. Moreover, the analysis shows that a single mode behaviour of the propagating radiation is required to avoid modal interference that could misinterpret the readout signal. © 2015 IOP Publishing Ltd.

  • Simulation and characterization of hollow microbridge resonators for label-free biosensing

    Marquez S., Alvarez M., Farina D., Dominguez C., Lechuga L.M. Progress in Biomedical Optics and Imaging - Proceedings of SPIE; 9518 ( 95180U) 2015. 10.1117/12.2178981. IF: 0.000

    In this work we describe the use of a micro-scale array of polysilicon doubly clamped beams, based on the approach of embedding microfluidic channels inside the resonators, as an innovative platform for multiplexed biosensors. Finite element methods in COMSOL were employed to simulate the structural mechanical behavior and to know the conditions to determine the frequency response in order to achieve optimal sensitivities and quality factors. Particularly, we studied the effect of microchannel cross-section area, length and sidewall thickness respect to the microchannel dimensions with the objective of injecting solutions of different densities. By integrating additional multiphysics models we analyzed the governing microfluidics, and we estimated that a maximum pressure difference of 7 MPa along the microchannels is required to establish an optimum water flow rate of 0.1 μl/min, which is adequate for biosensor applications. To validate the simulations we compared the thermal noise response of a fabricated array of microbridges in air, and we obtained resonant frequencies between 700 KHz and 1 MHz, in good agreement with our simulated results but with downward frequency shifts due to the undercut effect after fabrication. © 2015 SPIE.

  • Study of a low-cost trimodal polymer waveguide for interferometric optical biosensors

    Ramirez J.C., Lechuga L.M., Gabrielli L.H., Hernandez-Figueroa H.E. Optics Express; 23 (9): 11985 - 11994. 2015. 10.1364/OE.23.011985. IF: 3.488

    A novel evanescent wave biosensor based on modal interaction between the fundamental mode and the second order mode is proposed and numerically demonstrated. By taking advantage of their symmetries, it is possible to design a device where only the fundamental and the second order modes can propagate, without excitation of the first order mode. With this selection of modes it is possible to achieve a high sensitivity behavior in the biosensor configuration, due to the strong interaction between the evanescent field and the outer surface as compared to previous evanescent wave-based biosensor designs. © 2015 Optical Society of America.

  • Tailored Height Gradients in Vertical Nanowire Arrays via Mechanical and Electronic Modulation of Metal-Assisted Chemical Etching

    Otte M.A., Solis-Tinoco V., Prieto P., Borrisé X., Lechuga L.M., González M.U., Sepulveda B. Small; 11 (33): 4201 - 4208. 2015. 10.1002/smll.201500175. IF: 8.368

    In current top-down nanofabrication methodologies the design freedom is generally constrained to the two lateral dimensions, and is only limited by the resolution of the employed nanolithographic technique. However, nanostructure height, which relies on certain mask-dependent material deposition or etching techniques, is usually uniform, and on-chip variation of this parameter is difficult and generally limited to very simple patterns. Herein, a novel nanofabrication methodology is presented, which enables the generation of high aspect-ratio nanostructure arrays with height gradients in arbitrary directions by a single and fast etching process. Based on metal-assisted chemical etching using a catalytic gold layer perforated with nanoholes, it is demonstrated how nanostructure arrays with directional height gradients can be accurately tailored by: (i) the control of the mass transport through the nanohole array, (ii) the mechanical properties of the perforated metal layer, and (iii) the conductive coupling to the surrounding gold film to accelerate the local electrochemical etching process. The proposed technique, enabling 20-fold on-chip variation of nanostructure height in a spatial range of a few micrometers, offers a new tool for the creation of novel types of nano-assemblies and metamaterials with interesting technological applications in fields such as nanophotonics, nanophononics, microfluidics or biomechanics. Based on metal-assisted chemical etching using a catalytic gold layer perforated with nanoholes, it is demonstrated how high aspect-ratio nanostructure arrays with directional height gradients can be accurately tailored by: i) control of mass transport through the nanohole array, ii) mechanical properties of the perforated metal layer, and iii) conductive coupling to the surrounding gold film to accelerate the local electrochemical etching process. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


  • Nanoplasmonic biosensors for label-free deciphering of cellular pathways

    Huertas C.S., Lechuga L.M. Latin America Optics and Photonics Conference, LAOP 2014; 2014. 10.1364/laop.2014.lth1d.1.

    Nanoplasmonic biosensors can be employed as an unconventional strategy for deciphering main cell pathways influencing diseases progression. They can become advanced tools for early diagnosis and follow-up of therapies for several diseases as cancer. © OSA 2014.

  • Optimization study of bimodal waveguide interferometric biosensors

    Grajales D., Lechuga L.M. Optics InfoBase Conference Papers; 2014. .

    [No abstract available]

  • Optimization study of bimodal waveguide interferometric biosensors

    Grajales D., Lechuga L.M. Optics InfoBase Conference Papers; 2014. .

    [No abstract available]

  • Point-of-care diagnostics using integrated optical-based interferometric nanobiosensors

    Duval D., González-Guerrero A.B., Dante S., Huertas C.S., Maldonado J., Lechuga L.M. Optical Sensors, 2014; 2014. 10.1364/sensors.2014.seth3b.4.

    We present our last advances towards the achievement of a portable and label-free point-of-care platform based on bimodal waveguide interferometers for proteomics, genomics, and environmental applications. © 2014 OSA.

  • Wavelength modulated bimodal interferometer for highly sensitive biosensing applications

    Dante S., Duval D., González-Guerrero A.B., Fariña D., Domínguez C., Lechuga L.M. Optical Sensors, 2014; 2014. 10.1364/sensors.2014.seth2c.5.

    With the final goal of implementing a Lab-on-Chip platform for highly sensitive biosensing applications, we demonstrate a phase modulation approach based on all-optical principles for integrated hetero-modal interferometers. © 2014 OSA.


  • Integrated Optical Devices for Lab-on-a-chip Biosensing Applications.

    M.-Carmen Estevez; Mar Alvarez; Laura M. Lechuga Laser and Photonics Reviews; 2011. 10.1002/Ipor.201100025.


  • Biosensing microsystems: fast, label-free, real-time clinical testing

    Laura M. Lechuga; Orlando E. Hidalgo Alonso; Kiril Zinoviev; Carlos Dominguez; J. Elizalde SPIE Newsroom; 2008. .