Staff directory

Laura Lechuga Gómez

CSIC Research Professor and Group Leader
NanoBiosensors and Bioanalytical Applications



  • 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.

    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.

    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.

    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.

    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.

    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.

    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.

    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

  • 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.

    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.

  • 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.

    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.


  • 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.

    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.

    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.

    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.

    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.

    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.

    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.

    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 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.

    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.

    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.

    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.

    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.

  • 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.

    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.

    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.

    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.