Staff directory Arben Merkoçi Hyka

Arben Merkoçi Hyka

ICREA Research Professor and Group Leader
arben.merkoci(ELIMINAR)@icn2.cat
Nanobioelectronics and Biosensors

ORCID: 0000-0003-2486-8085

Publications

2017

Biosensors for plant pathogen detection
Khater M., de la Escosura-Muñiz A., Merkoçi A. Biosensors and Bioelectronics; 93: 72 - 86. 2017. 10.1016/j.bios.2016.09.091. IF: 7.780

Infectious plant diseases are caused by pathogenic microorganisms such as fungi, bacteria, viruses, viroids, phytoplasma and nematodes. Worldwide, plant pathogen infections are among main factors limiting crop productivity and increasing economic losses. Plant pathogen detection is important as first step to manage a plant disease in greenhouses, field conditions and at the country boarders. Current immunological techniques used to detect pathogens in plant include enzyme-linked immunosorbent assays (ELISA) and direct tissue blot immunoassays (DTBIA). DNA-based techniques such as polymerase chain reaction (PCR), real time PCR (RT-PCR) and dot blot hybridization have also been proposed for pathogen identification and detection. However these methodologies are time-consuming and require complex instruments, being not suitable for in-situ analysis. Consequently, there is strong interest for developing new biosensing systems for early detection of plant diseases with high sensitivity and specificity at the point-of-care. In this context, we revise here the recent advancement in the development of advantageous biosensing systems for plant pathogen detection based on both antibody and DNA receptors. The use of different nanomaterials such as nanochannels and metallic nanoparticles for the development of innovative and sensitive biosensing systems for the detection of pathogens (i.e. bacteria and viruses) at the point-of-care is also shown. Plastic and paper-based platforms have been used for this purpose, offering cheap and easy-to-use really integrated sensing systems for rapid on-site detection. Beside devices developed at research and development level a brief revision of commercially available kits is also included in this review. © 2016 Elsevier B.V.

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Electrochemically reduced graphene and iridium oxide nanoparticles for inhibition-based angiotensin-converting enzyme inhibitor detection
Kurbanoglu S., Rivas L., Ozkan S.A., Merkoçi A. Biosensors and Bioelectronics; 88: 122 - 129. 2017. 10.1016/j.bios.2016.07.109. IF: 7.780

In this work, a novel biosensor based on electrochemically reduced graphene oxide and iridium oxide nanoparticles for the detection of angiotensin-converting enzyme inhibitor drug, captopril, is presented. For the preparation of the biosensor, tyrosinase is immobilized onto screen printed electrode by using 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide and N-Hydroxysuccinimide coupling reagents, in electrochemically reduced graphene oxide and iridium oxide nanoparticles matrix. Biosensor response is characterized towards catechol, in terms of graphene oxide concentration, number of cycles to reduce graphene oxide, volume of iridium oxide nanoparticles and tyrosinase solution. The designed biosensor is used to inhibit tyrosinase activity by Captopril, which is generally used to treat congestive heart failure. It is an angiotensin-converting enzyme inhibitor that operates via chelating copper at the active site of tyrosinase and thioquinone formation. The captopril detections using both inhibition ways are very sensitive with low limits of detection: 0.019 µM and 0.008 µM for chelating copper at the active site of tyrosinase and thioquinone formation, respectively. The proposed methods have been successfully applied in captopril determination in spiked human serum and pharmaceutical dosage forms with acceptable recovery values. © 2016 Elsevier B.V.

View abstract
Graphene Oxide-Poly(dimethylsiloxane)-Based Lab-on-a-Chip Platform for Heavy-Metals Preconcentration and Electrochemical Detection
Chałupniak A., Merkoçi A. ACS Applied Materials and Interfaces; 9 (51): 44766 - 44775. 2017. 10.1021/acsami.7b12368. IF: 7.504

Herein, we present the application of a novel graphene oxide-poly(dimethylsiloxane) (GO-PDMS) composite in reversible adsorption/desorption, including detection of heavy metals. GO-PDMS was fabricated by simple blending of GO with silicon monomer in the presence of tetrahydrofuran, followed by polymerization initiated upon the addition of curing agent. We found GO concentration, curing agent concentration, pH, and contact time among the most important factors affecting the adsorption of Pb(II) used as a model heavy metal. The mechanism of adsorption is based on surface complexation, where oxygen active groups of negative charge can bind with bivalent metal ions Me(II). To demonstrate a practical application of this material, we fabricated microfluidic lab-on-a-chip platform for heavy-metals preconcentration and detection. This device consists of a screen-printed carbon electrode, a PDMS chip, and a GO-PDMS chip. The use of GO-PDMS preconcentration platform significantly improves the sensitivity of electrochemical detection of heavy metals (an increase of current up to 30× was observed), without the need of modifying electrodes or special reagents addition. Therefore, samples being so far below the limit of detection (0.5 ppb) were successfully detected. This approach is compatible also with real samples (seawater) as ionic strength was found as indifferent for the adsorption process. To the best of our knowledge, GO-PDMS was used for the first time in sensing application. Moreover, due to mechanical resistance and outstanding durability, it can be used multiple times unlike other GO-based platforms for heavy-metals adsorption. © 2017 American Chemical Society.

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Graphene-Based Biosensors: Going Simple
Morales-Narváez E., Baptista-Pires L., Zamora-Gálvez A., Merkoçi A. Advanced Materials; 29 (7, 1604905) 2017. 10.1002/adma.201604905. IF: 19.791

The main properties of graphene derivatives facilitating optical and electrical biosensing platforms are discussed, along with how the integration of graphene derivatives, plastic, and paper can lead to innovative devices in order to simplify biosensing technology and manufacture easy-to-use, yet powerful electrical or optical biosensors. Some crucial issues to be overcome in order to bring graphene-based biosensors to the market are also underscored. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

View abstract
Graphene-based hybrid for enantioselective sensing applications
Zor E., Morales-Narváez E., Alpaydin S., Bingol H., Ersoz M., Merkoçi A. Biosensors and Bioelectronics; 87: 410 - 416. 2017. 10.1016/j.bios.2016.08.074. IF: 7.780

Chirality is a major field of research of chemical biology and is essential in pharmacology. Accordingly, approaches for distinguishing between different chiral forms of a compound are of great interest. We report on an efficient and generic enantioselective sensor that is achieved by coupling reduced graphene oxide with γ-cyclodextrin (rGO/γ-CD). The enantioselective sensing capability of the resulting structure was operated in both electrical and optical mode for of tryptophan enantiomers (D-/L-Trp). In this sense, voltammetric and photoluminescence measurements were conducted and the experimental results were compared to molecular docking method. We gain insight into the occurring recognition mechanism with selectivity toward D- and L-Trp as shown in voltammetric, photoluminescence and molecular docking responses. As an enantioselective solid phase on an electrochemical transducer, thanks to the different dimensional interaction of enantiomers with hybrid material, a discrepancy occurs in the Gibbs free energy leading to a difference in oxidation peak potential as observed in electrochemical measurements. The optical sensing principle is based on the energy transfer phenomenon that occurs between photoexcited D-/L-Trp enantiomers and rGO/γ-CD giving rise to an enantioselective photoluminescence quenching due to the tendency of chiral enantiomers to form complexes with γ-CD in different molecular orientations as demonstrated by molecular docking studies. The approach, which is the first demonstration of applicability of molecular docking to show both enantioselective electrochemical and photoluminescence quenching capabilities of a graphene-related hybrid material, is truly new and may have broad interest in combination of experimental and computational methods for enantiosensing of chiral molecules. © 2016 Elsevier B.V.

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Graphene-encapsulated materials: Synthesis, applications and trends
Morales-Narváez E., Sgobbi L.F., Machado S.A.S., Merkoçi A. Progress in Materials Science; 86: 1 - 24. 2017. 10.1016/j.pmatsci.2017.01.001. IF: 31.140

Graphene-based materials (GBM) are an exceptional type of materials that offer unprecedented application capabilities to the scientific and technologic community. The encapsulation of different materials such as drugs, nanoparticles, polymers, oxides and cells by GBM is leading to outstanding hybrid materials with unprecedented behaviours promising a myriad of advantageous applications, including micro/nanomotors, biosensing platforms, bio/imaging agents, drug delivery systems, potential tumour treatment alternatives, environmental remediation platforms, advanced batteries and novel supercapacitors. We present an overview on graphene-encapsulated materials and their most important synthesis pathways. In addition, we explore the synergistic functionalities provided by these composites and highlight the state-of-the-art related to energy, environmental and bio-applications, among others. Finally, we discuss their challenges and future outlooks. © 2017 Elsevier Ltd

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Magnetic nanoparticle-molecular imprinted polymer: A new impedimetric sensor for tributyltin detection
Zamora-Gálvez A., Mayorga-Matinez C.C., Parolo C., Pons J., Merkoçi A. Electrochemistry Communications; 82: 6 - 11. 2017. 10.1016/j.elecom.2017.07.007. IF: 4.396

Recently, molecular imprinted polymers (MIPs) were extensively used for separation and identification of specific molecules, replacing expensive and unstable biological receptors. Nonetheless, their application in electrochemical sensors has not been sufficiently explored. Here we report the use of a MIP as a specific receptor in a new highly sensitive tributyltin (TBT) electrochemical sensor. The sensor combines the specificity, pre-concentration capability and robustness of molecular imprinted polymer attached onto magnetic nanoparticles with the quantitative outputs of impedimetric measurements. The proposed device detects TBT in a concentration range of 5 pM to 5 μM with a low limit of detection (5.37 pM), which is lower than the one recommended for TBT in sea water by the US Environmental Protection Agency (EPA). We believe that this new electrochemical sensor can play an important role in the monitoring of the quality of sea and fresh waters worldwide. © 2017 Elsevier B.V.

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Mobile phone-based biosensing: An emerging “diagnostic and communication” technology
Quesada-González D., Merkoçi A. Biosensors and Bioelectronics; 92: 549 - 562. 2017. 10.1016/j.bios.2016.10.062. IF: 7.780

In this review we discuss recent developments on the use of mobile phones and similar devices for biosensing applications in which diagnostics and communications are coupled. Owing to the capabilities of mobile phones (their cameras, connectivity, portability, etc.) and to advances in biosensing, the coupling of these two technologies is enabling portable and user-friendly analytical devices. Any user can now perform quick, robust and easy (bio)assays anywhere and at any time. Among the most widely reported of such devices are paper-based platforms. Herein we provide an overview of a broad range of biosensing possibilities, from optical to electrochemical measurements; explore the various reported designs for adapters; and consider future opportunities for this technology in fields such as health diagnostics, safety & security, and environment monitoring. © 2016 Elsevier B.V.

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Nanocellulose in Sensing and Biosensing
Golmohammadi H., Morales-Narváez E., Naghdi T., Merkoçi A. Chemistry of Materials; 29 (13): 5426 - 5446. 2017. 10.1021/acs.chemmater.7b01170. IF: 9.466

Because of its multifunctional character, nanocellulose (NC) is one of the most interesting nature-based nanomaterials and is attracting attention in a myriad of fields such as biomaterials, engineering, biomedicine, opto/electronic devices, nanocomposites, textiles, cosmetics and food products. Moreover, NC offers a plethora of outstanding properties, including inherent renewability, biodegradability, commercial availability, flexibility, printability, low density, high porosity, optical transparency as well as extraordinary mechanical, thermal and physicochemical properties. Consequently, NC holds unprecedented capabilities that are appealing to the scientific, technologic and industrial community. In this review, we highlight how NC is being tailored and applied in (bio)sensing technology, whose results aim at displaying analytical information related to various fields such as clinical/medical diagnostics, environmental monitoring, food safety, physical/mechanical sensing, labeling and bioimaging applications. In fact, NC-based platforms could be considered an emerging technology to fabricate efficient, simple, cost-effective and disposable optical/electrical analytical devices for several (bio)sensing applications including health care, diagnostics, environmental monitoring, food quality control, forensic analysis and physical sensing. We foresee that many of the (bio)sensors that are currently based on plastic, glass or conventional paper platforms will be soon transferred to NC and this generation of (bio)sensing platforms could revolutionize the conventional sensing technology. © 2017 American Chemical Society.

View abstract
Nanomaterials connected to antibodies and molecularly imprinted polymers as bio/receptors for bio/sensor applications
Zamora-Gálvez A., Morales-Narváez E., Mayorga-Martinez C.C., Merkoçi A. Applied Materials Today; 9: 387 - 401. 2017. 10.1016/j.apmt.2017.09.006. IF: 0.000

Nowadays, nanomaterials are considered a pivotal tool for different fields such as textiles, energy, environment, electronics, photonics, food, agriculture, biomedicine and health care. This is due to their advantageous properties coming from their high surface area, among other physicochemical properties, compared to their respective bulk forms. Nanomaterials, while used in (bio)detection systems, have shown to be extremely valuable to improve the analytical performance of conventional/laboratory methods and move forward biosensing technology. The usage of nanomaterials has been widely spread over the last few years mainly thanks to the great advantages that they offer in the development of conceptually new biosensors or improving the existing ones. This review focuses on how the usage of different nanomaterials have impacted biosensing research underscoring two different types of receptors, including biological receptors such as antibodies and non-biological receptors like molecularly imprinted polymers. The performance of relevant biosensing platforms including lateral flow devices as well as other optical and electrochemical approaches integrating nanomaterials and (bio) receptors are also discussed. © 2017 Elsevier Ltd

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Nanomaterials-based enzyme electrochemical biosensors operating through inhibition for biosensing applications
Kurbanoglu S., Ozkan S.A., Merkoçi A. Biosensors and Bioelectronics; 89: 886 - 898. 2017. 10.1016/j.bios.2016.09.102. IF: 7.780

In recent years great progress has been made in applying nanomaterials to design novel biosensors. Use of nanomaterials offers to biosensing platforms exceptional optical, electronic and magnetic properties. Nanomaterials can increase the surface of the transducing area of the sensors that in turn bring an increase in catalytic behaviors. They have large surface-to-volume ratio, controlled morphology and structure that also favor miniaturization, an interesting advantage when the sample volume is a critical issue. Biosensors have great potential for achieving detect-to-protect devices: devices that can be used in detections of pollutants and other treating compounds/analytes (drugs) protecting citizens' life. After a long term focused scientific and financial efforts/supports biosensors are expected now to fulfill their promise such as being able to perform sampling and analysis of complex samples with interest for clinical or environment fields. Among all types of biosensors, enzymatic biosensors, the most explored biosensing devices, have an interesting property, the inherent inhibition phenomena given the enzyme-substrate complex formation. The exploration of such phenomena is making remarkably important their application as research and applied tools in diagnostics. Different inhibition biosensor systems based on nanomaterials modification has been proposed and applied. The role of nanomaterials in inhibition-based biosensors for the analyses of different groups of drugs as well as contaminants such as pesticides, phenolic compounds and others, are discussed in this review. This deep analysis of inhibition-based biosensors that employ nanomaterials will serve researchers as a guideline for further improvements and approaching of these devices to real sample applications so as to reach society needs and such biosensor market demands. © 2016 Elsevier B.V.

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Nanomaterials-Based Platforms for Environmental Monitoring
Pino F., Mayorga-Martinez C.C., Merkoçi A. Comprehensive Analytical Chemistry; 77: 207 - 236. 2017. 10.1016/bs.coac.2017.06.002.

This chapter reviews the latest development of new nanomaterials-based biosensing platforms for environmental monitoring. In particular, we focus our attention in the analysis of different electrochemical analytical systems reported in the last 10 years. Various platforms will be described, pointing out their advantages and also the possible disadvantages. Biosensing platforms are becoming useful devices for environmental monitoring in particular for the use as screening tests for in situ measurement. Some of them are even being commercialized for detection of pollutants like the ones for the detection of heavy metals in different water samples. At the same time the recent years have shown development in the preparation, functionalization and characterisation of new nanomaterials. The new biosensing platforms made using these materials, given the improved analytical performance, could nowadays be an alternative to standard analytical instrumentation for in-field applications. For better understanding of these new electrochemical devices we discuss different nanomaterials (metal nanoparticles, carbon nanotubes, quantum dot and graphene) used not only for the modification of the electrode surface for enhancing the transfer of charge but also as carriers/supporting matrix of the biological recognition element (e.g., enzyme, antibody). The employed nanomaterials have clearly improved the effectiveness of the biosensing in addition of offering also new detection alternatives for various pollutants present in the environment. © 2017 Elsevier B.V.

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Paper strip-embedded graphene quantum dots: A screening device with a smartphone readout
Álvarez-DIduk R., Orozco J., Merkoçi A. Scientific Reports; 7 (1, 976) 2017. 10.1038/s41598-017-01134-3. IF: 4.259

Simple, inexpensive and rapid sensing systems are very demanded for a myriad of uses. Intrinsic properties of emerging paper-based analytical devices have demonstrated considerable potential to fulfill such demand. This work reports an easy-to-use, low cost, and disposable paper-based sensing device for rapid chemical screening with a smartphone readout. The device comprises luminescent graphene quantum dots (GQDs) sensing probes embedded into a nitrocellulose matrix where the resonance energy transfer phenomenon seems to be the sensing mechanism. The GQDs probes were synthesized from citric acid by a pyrolysis procedure, further physisorbed and confined into small wax-traced spots on the nitrocellulose substrate. The GQDs were excited by an UV LED, this, is powered by a smartphone used as both; energy source and imaging capture. The LED was contained within a 3D-printed dark chamber that isolates the paper platform from external light fluctuations leading to highly reproducible data. The cellulose-based device was proven as a promising screening tool for phenols and polyphenols in environmental and food samples, respectively. It opens up new opportunities for simple and fast screening of organic compounds and offers numerous possibilities for versatile applications. It can be especially useful in remote settings where sophisticated instrumentation is not always available. © 2017 The Author(s).

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Production of biofunctionalized MoS2 flakes with rationally modified lysozyme: A biocompatible 2D hybrid material
Siepi M., Morales-Narváez E., Domingo N., Monti D.M., Notomista E., Merkoçi A. 2D Materials; 4 (3, 035007) 2017. 10.1088/2053-1583/aa7966. IF: 6.937

Bioapplications of 2D materials embrace demanding features in terms of environmental impact, toxicity and biocompatibility. Here we report on the use of a rationally modified lysozyme to assist the exfoliation of Mos2 bulk crystals suspended in water through ultrasonic exfoliation. The design of the proposed lysozyme derivative provides this exfoliated 2D-materail with both, hydrophobic groups that interact with the surface of Mos2 and hydrophilic groups exposed to the aqueous medium, which hinders its re-Aggregation. This approach, clarified also by molecular docking studies, leads to a stable material (ζ-potential, 27 ?} 1 mV) with a yield of up to 430 μg ml-1. The bio-hybrid material was characterized in terms of number of layers and optical properties according to different slots separated by diverse centrifugal forces. Furthermore the obtained material was proved to be biocompatible using human normal keratinocytes and human cancer epithelial cells, whereas the method was demonstrated to be applicable to produce other 2D materials such as graphene. This approach is appealing for the advantageous production of high quality Mos2 flakes and their application in biomedicine and biosensing. Moreover, this method can be applied to different starting materials, making the denatured lysozyme a promising bio-Tool for surface functionalization of 2D materials. © 2017 IOP Publishing Ltd.

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Rapid on-chip apoptosis assay on human carcinoma cells based on annexin-V/quantum dot probes
Montón H., Medina-Sánchez M., Soler J.A., Chałupniak A., Nogués C., Merkoçi A. Biosensors and Bioelectronics; 94: 408 - 414. 2017. 10.1016/j.bios.2017.03.034. IF: 7.780

Despite all the efforts made over years to study the cancer expression and the metastasis event, there is not a clear understanding of its origins and effective treatment. Therefore, more specialized and rapid techniques are required for studying cell behaviour under different drug-based treatments. Here we present a quantum dot signalling-based cell assay carried out in a segmental microfluidic device that allows studying the effect of anti-cancer drugs in cultured cell lines by monitoring phosphatidylserine translocation that occurs in early apoptosis. The developed platform combines the automatic generation of a drug gradient concentration, allowing exposure of cancer cells to different doses, and the immunolabeling of the apoptotic cells using quantum dot reporters. Thereby a complete cell-based assay for efficient drug screening is performed showing a clear correlation between drug dose and amount of cells undergoing apoptosis. © 2017 Elsevier B.V.

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Recent trends in nanomaterials integration into simple biosensing platforms
Chalupniak A., Merkoçi A. Nanotechnology in Biology and Medicine: Methods, Devices, and Applications, Second Edition; : 389 - 405. 2017. 10.4324/9781315374581.

Development of new biosensors is conditioned by progress in the field of nanotechnology and nanomaterials between other fields. This chapter discusses the role of some promising nanomaterials, which can provide efficient, more sensitive, and versatile biosensing strategies. Most of them can be employed in electrochemical and optical biosensors working like labels, signal transducers, or substrates for biosensors’ platforms. Application of different types of nanoparticles, Quantum Dots, and carbon nanomaterials in paper-based biosensors, Lab-On-a-Chip devices, microarrays, and other (bio)sensors is presented. © 2018 by Taylor & Francis Group, LLC.

View abstract
Straightforward Immunosensing Platform Based on Graphene Oxide-Decorated Nanopaper: A Highly Sensitive and Fast Biosensing Approach
Cheeveewattanagul N., Morales-Narváez E., Hassan A.-R.H.A., Bergua J.F., Surareungchai W., Somasundrum M., Merkoçi A. Advanced Functional Materials; 27 (38, 1702741) 2017. 10.1002/adfm.201702741. IF: 12.124

Immunoassays are nowadays a crucial tool for diagnostics and drug development. However, they often involve time-consuming procedures and need at least two antibodies in charge of the capture and detection processes, respectively. This study reports a nanocomposite based on graphene oxide-coated nanopaper (GONAP) facilitating an advantageous immunosensing platform using a single antibody and without the need for washing steps. The hydrophilic, porous, and photoluminescence-quenching character of GONAP allows for the adsorption and quenching of photoluminescent quantum dots nanocrystals complexed with antibodies (Ab-QDs), enabling a ready-to-use immunosensing platform. The photoluminescence is recovered upon immunocomplex (antibody-antigen) formation which embraces a series of interactions (hydrogen bonding, electrostatic, hydrophobic, and Van der Waals interactions) that trigger desorption of the antigen-Ab-QD complex from GONAP surface. However, the antigen is then attached onto the GONAP surface by electrostatic interactions leading to a spacer (greater than ≈20 nm) between Ab-QDs and GONAP and thus hindering nonradiative energy transfer. It is demonstrated that this simple—yet highly sensitive—platform represents a virtually universal immunosensing approach by using small-sized and big-sized targets as model analytes, those are, human-IgG protein and Escherichia coli bacteria. In addition, the assay is proved effective in real matrices analysis, including human serum, poultry meat, and river water. GONAP opens the way to conceptually new paper-based devices for immunosensing, which are amenable to point of care applications and automated diagnostics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

View abstract
Toward integrated detection and graphene-based removal of contaminants in a lab-on-a-chip platform
Chałupniak A., Merkoçi A. Nano Research; 10 (7): 2296 - 2310. 2017. 10.1007/s12274-016-1420-3. IF: 7.354

A novel, miniaturized microfluidic platform was developed for the simultaneous detection and removal of polybrominated diphenyl ethers (PBDEs). The platform consists of a polydimethylsiloxane (PDMS) microfluidic chip for an immunoreaction step, a PDMS chip with an integrated screen-printed electrode (SPCE) for detection, and a PDMS-reduced graphene oxide (rGO) chip for physical adsorption and subsequent removal of PBDE residues. The detection was based on competitive immunoassay-linked binding between PBDE and PBDE modified with horseradish peroxidase (HRP-PBDE) followed by the monitoring of enzymatic oxidation of o-aminophenol (o-AP) using square wave anodic stripping voltammetry (SW-ASV). PBDE was detected with good sensitivity and a limit of detection similar to that obtained with a commercial colorimetric test (0.018 ppb), but with the advantage of using lower reagent volumes and a reduced analysis time. The use of microfluidic chips also provides improved linearity and a better reproducibility in comparison to those obtained with batch-based measurements using screen-printed electrodes. In order to design a detection system suitable for toxic compounds such as PBDEs, a reduced graphene oxide–PDMS composite was developed and optimized to obtain increased adsorption (based on both the hydrophobicity and π–π stacking between rGO and PBDE molecules) compared to those of non-modified PDMS. To the best of our knowledge, this is the first demonstration of electrochemical detection of flame retardants and a novel application of the rGO-PDMS composite in a biosensing system. This system can be easily applied to detect any analyte using the appropriate immunoassay and it supports operation in complex matrices such as seawater. [Figure not available: see fulltext.]. © 2016, Tsinghua University Press and Springer-Verlag Berlin Heidelberg.

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2016

Bio(Sensing) devices based on ferrocene–functionalized graphene and carbon nanotubes
Rabti A., Raouafi N., Merkoçi A. Carbon; 108: 481 - 514. 2016. 10.1016/j.carbon.2016.07.043. IF: 6.198

Both carbon nanotubes (CNTs) and graphene are important pillars in the ongoing efforts to devise new applications in nanotechnology. One of their most promising applications is building devices such as sensors and biosensors, which is important step for the development of personalized medical healthcare devices. Mediators are usually used and sought to modify the physicochemical properties of these materials. In this review, we highlight the importance of the functionalization of CNT and graphene derivatives with redox molecules taking ferrocene derivatives as a model molecule. The employed techniques during (bio)sensing measurements using various functionalization strategies are also described. In addition, we discuss various aspects related to the applications of ferrocene–modified CNTs and graphene in electrochemical sensors and biosensors with a focus on the explanation of both CNTs/graphene and ferrocene contributions in the catalytic systems, which in turn enhance the analytical performance of the (bio)sensing devices. © 2016 Elsevier Ltd

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Bismuth-Based Nanomaterials and Platforms for Sensing and Biosensing Applications
Cadevall M., Ros J., Merkoçi A. Functional and Physical Properties of Polymer Nanocomposites; : 159 - 181. 2016. 10.1002/9781118542316.ch8.

Bismuth (Bi) has a high electrical resistance and the thermal conductivity is lower than any other metal except mercury; considering that, Bi is sometimes called a semimetal. These semi metallic properties are particularly interesting for its use as a thermoelectric material because of its low effective mass, highly anisotropic Fermi surface, and its potential to induce a semimetal/semiconductor transition with decreasing crystallite size that is typical for soft metals. This chapter discusses some examples of Bi-based systems for both sensing and biosensing. It shows the most advanced methodologies for synthesis of Bi nanostructures of different shapes and sizes based on the use of different reducing and stabilizing agents. The biocompatibility of Bi makes possible the conjugation of Bi nanostructures with enzymes and antibodies. The analysis of organic compounds, pharmaceutical substances, and pesticides as well as other compounds of biological relevance is also achieved by using Bi-based biosensors. © 2016 John Wiley & Sons, Ltd. All rights reserved.

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Control of Electron-transfer in Immunonanosensors by Using Polyclonal and Monoclonal Antibodies
Mars A., Parolo C., de la Escosura-Muñiz A., Raouafi N., Merkoçi A. Electroanalysis; 28 (8): 1795 - 1802. 2016. 10.1002/elan.201500646. IF: 2.471

The design and operation of biosensors is not trivial. For instance, variation in the output signal during monitoring of analytes can not usually be controlled. Hence, if such control were possible, and could be triggered on demand, it would greatly facilitate system design and operation. Herein, we report the design of two types of voltamperometric immunosensors, in which the magnitude of the current output signal (differential pulse voltammetry [DPV]) can be increased or decreased as needed. The designed systems use monoclonal and polyclonal anti-human IgG antibodies, conjugated to monopodal ferrocene-modified gold nanoparticles that are casted onto screen-printed carbon electrodes (Ab/mFcL/AuNPs/SPCEs). Upon addition of human IgG as antigen, the systems exhibit opposite responses according to the Ab: the current decreases when monoclonal Ab is used, whereas it increases when polyclonal Ab is used. We attributed the former response to inhibition of electron-transfer (due to the formation of a protein layer), and the latter response, to a global increase in electron transfer (induced by the aggregation of gold nanoparticles). These effects were confirmed by studying a custom-made lipoic acid-based bipodal ligand, which confirmed that the increase in current is effectively induced by the aggregation of the modified nanoparticles (pAb/mFcL/AuNPs). Both sensors have large dynamic ranges, although the pAb-based one was found to be 3.3-times more sensitive. Tests of selectivity and specificity for ovalbumin, α-lactalbumin and serum bovine albumin showed that the immunosensors are highly selective and specific, even in the presence of up to 1000-fold levels of potentially competitive proteins. The limit of detection for human IgG using the pAb/mFcL/AuNP bioconjugate was estimated to be 0.85 ng/mL. The pAb/mFcL/AuNPs-based biosensor has used to determine amounts of human IgG in real sample. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

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Corrigendum to 'Microfluidic platform for environmental contaminants sensing and degradation based on boron-doped diamond electrodes' [Biosens. Bioelectron. 08/75 (2015) 365-374].doi: 10.1016/j.bios.2015.08.058.
Medina-Sánchez M., Mayorga-Martinez C.C., Watanabe T., Ivandini T.A., Honda Y., Pino F., Nakata K., Fujishima A., Einaga Y., Merkoçi A. Biosensors and Bioelectronics; 79: 946. 2016. 10.1016/j.bios.2015.10.087.

[No abstract available]

View abstract
Detection of parathyroid hormone-like hormone in cancer cell cultures by gold nanoparticle-based lateral flow immunoassays
Chamorro-Garcia A., de la Escosura-Muñiz A., Espinoza-Castañeda M., Rodriguez-Hernandez C.J., de Torres C., Merkoçi A. Nanomedicine: Nanotechnology, Biology, and Medicine; 12 (1): 53 - 61. 2016. 10.1016/j.nano.2015.09.012. IF: 5.671

Parathyroid hormone-like hormone (PTHLH) exerts relevant roles in progression and dissemination of several tumors. However, factors influencing its production and secretion have not been fully characterized. The main limitation is the lack of specific, sensitive and widely available techniques to detect and quantify PTHLH. We have developed a lateral flow immunoassay using gold nanoparticles label for the fast and easy detection of PTHLH in lysates and culture media of three human cell lines (HaCaT, LA-N-1, SK-N-AS). Levels in culture media and lysates ranged from 11 to 20 ng/mL and 0.66 to 0.87 μg/mL respectively. Results for HaCaT are in agreement to the previously reported, whereas LA-N-1 and SK-N-AS have been evaluated for the first time. The system also exhibits good performance in human serum samples. This methodology represents a helpful tool for future in vitro and in vivo studies of mechanisms involved in PTHLH production as well as for diagnostics. From the Clinical Editor: Parathyroid Hormone-like Hormone (PTHLH) is known to be secreted by some tumors. However, the detection of this peptide remains difficult. The authors here described their technique of using gold nanoparticles as label for the detection of PTHLH by Lateral-flow immunoassays (LFIAs). The positive results may also point a way to using the same technique for the rapid determination of other relevant cancer proteins. © 2015 Elsevier Inc.

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Emerging Nanomaterials for Analytical Detection
Alarcon-Angeles G., Álvarez-Romero G.A., Merkoçi A. Comprehensive Analytical Chemistry; 74: 195 - 246. 2016. 10.1016/bs.coac.2016.03.022. IF: 0.000

This chapter revises the recent trends in the use and applications of nanomaterials (NMs) in analytical detections with special interest in food quality control. The most important NMs such as gold nanoparticles, quantum dots, carbon-related nanomaterials and their properties are introduced. We show how analytical science is taking advantage of such materials to either develop new analytical methods or improve the existing technologies. Biosensing, in both batch and lab-on-a-chip formats, is one of the most important analytical technologies that is in the forefront of such interesting applications. The use of these materials in some conventional analytical techniques such as chromatography between others also is discussed. Examples related to such NMs application in real food samples with interest for quality control as well as detection of various interesting compounds such as glucose, amino acids, DNA (normally present in food) or other species that are usually of interest to be detected for safety reasons (bacteria, toxins) are discussed. Aspects related to the improvements of analytical performance in terms of detection limits, stability, selectivity, etc. using various NMs and detection technologies also are discussed. © 2016 Elsevier B.V.

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Enhanced detection of quantum dots labeled protein by simultaneous bismuth electrodeposition into microfluidic channel
Medina-Sánchez M., Miserere S., Cadevall M., Merkoçi A. Electrophoresis; 37 (3): 432 - 437. 2016. 10.1002/elps.201500288. IF: 2.482

In this study, we propose an electrochemical immunoassay into a disposable microfluidic platform, using quantum dots (QDs) as labels and their enhanced detection using bismuth as an alternative to mercury electrodes. CdSe@ZnS QDs were used to tag human IgG as a model protein and detected through highly sensitive stripping voltammetry of the dissolved metallic component (cadmium in our case). The modification of the screen printed carbon electrodes (SPCEs) was done by a simple electrodeposition of bismuth that was previously mixed with the sample containing QDs. A magneto-immunosandwich assay was performed using a micromixer. A magnet placed at its outlet in order to capture the magnetic beads used as solid support for the immunoassay. SPCEs were integrated at the end of the channel as detector. Different parameters such as bismuth concentration, flow rate, and incubation times, were optimized. The LOD for HIgG in presence of bismuth was 3.5 ng/mL with a RSD of 13.2%. This LOD was about 3.3-fold lower than the one obtained without bismuth. Furthermore, the sensitivity of the system was increased 100-fold respect to experiments carried out with classical screen-printed electrodes, both in presence of bismuth. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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Ferrocene-functionalized graphene electrode for biosensing applications
Rabti A., Mayorga-Martinez C.C., Baptista-Pires L., Raouafi N., Merkoçi A. Analytica Chimica Acta; 926: 28 - 35. 2016. 10.1016/j.aca.2016.04.010. IF: 4.712

A novel ferrocene-functionalized reduced graphene oxide (rGO)-based electrode is proposed. It was fabricated by the drop casting of ferrocene-functionalized graphene onto polyester substrate as the working electrode integrated within screen-printed reference and counter electrodes. The ferrocene-functionalized rGO has been fully characterized using FTIR, XPS, contact angle measurements, SEM and TEM microscopy, and cyclic voltammetry. The XPS and EDX analysis showed the presence of Fe element related to the introduced ferrocene groups, which is confirmed by a clear CV signal at ca. 0.25 V vs. Ag/AgCl (0.1 KCl). Mediated redox catalysis of H2O2 and bio-functionalization with glucose oxidase for glucose detection were achieved by the bioelectrode providing a proof for potential biosensing applications. © 2016 Elsevier B.V.

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Graphene-based Janus micromotors for the dynamic removal of pollutants
Orozco J., Mercante L.A., Pol R., Merkoçi A. Journal of Materials Chemistry A; 4 (9): 3371 - 3378. 2016. 10.1039/c5ta09850e. IF: 8.262

Persistent organic pollutants (POPs) are ubiquitous in the environment as a result of modern industrial processes. We present an effective POPs decontamination strategy based on their dynamic adsorption at the surface of reduced graphene oxide (rGO)-coated silica (SiO2)-Pt Janus magnetic micromotors for their appropriate final disposition. While the motors rapidly move in a contaminated solution, the adsorption of POPs efficiently takes place in a very short time. Characterization of the micromotors both from the materials and from the motion point of view was performed. Polybrominated diphenyl ethers (PBDEs) and 5-chloro-2-(2,4-dichlorophenoxy) phenol (triclosan) were chosen as model POPs and the removal of the contaminants was efficiently achieved. The rGO-coated micromotors demonstrated superior adsorbent properties with respect to their concomitant GO-coated micromotors, static rGO-coated particles and dynamic silica micromotors counterparts. The extent of decontamination was studied over the number of micromotors, whose magnetic properties were used for their collection from environmental samples. The adsorption properties were maintained for 4 cycles of micromotors reuse. The new rGO-coated SiO2 functional material-based micromotors showed outstanding capabilities towards the removal of POPs and their further disposition, opening up new possibilities for efficient environmental remediation of these hazardous compounds. © 2016 The Royal Society of Chemistry.

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High-performance sensor based on copper oxide nanoparticles for dual detection of phenolic compounds and a pesticide
Pino F., Mayorga-Martinez C.C., Merkoçi A. Electrochemistry Communications; 71: 33 - 37. 2016. 10.1016/j.elecom.2016.08.001. IF: 4.569

The development of nanomaterials for use as bio-recognition elements is important in the evolution of biosensing systems. In the present article we present a sensing system based on copper oxide nanoparticles (CuO NPs) for the detection of phenolic compounds and pesticides. This sensor takes advantage of the interactions of CuO NPs with toxic compounds that in turn generate an electrochemical signal related to the concentration of the pollutants. © 2016

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Hybrid self-assembled materials constituted by ferromagnetic nanoparticles and tannic acid: A theoretical and experimental investigation
Santos A.F.M., Macedo L.J.A., Chaves M.H., Espinoza-Castañeda M., Merkoçi A., Limac F.D.C.A., Cantanhêde W. Journal of the Brazilian Chemical Society; 27 (4): 727 - 734. 2016. 10.5935/0103-5053.20150322. IF: 1.096

Hybrid magnetite materials are interesting for both biomedical and catalytic applications due to their well-known biocompatibility, as well as their magnetic and electric properties. In this work we prepared Fe3 O4 nanoparticles (NPs) coated with tannic acid (TA), a natural polyphenol, through two different synthetic routes, aiming to understand the influence of TA in the synthesis step and contribute to the development of water-dispersible magnetic materials. The coating process was verified by information obtained from transmission electron microscopy (TEM), zeta-potential and Fourier transform infrared (FTIR) spectroscopy. The incorporation of TA after Fe3 O4 NPs production generated spherical NPs smaller than 10 nm, suggesting that TA plays a fundamental role in the nucleation and organization of Fe3 O4 NPs. Data from both density functional theory (DFT) and FTIR allowed us to infer that Fe3 O4 interacts mainly with the carbonyl groups of TA. Hybrid materials having improved water-dispersibility are very attractive for biomedical applications. ©2016 Sociedade Brasileira de Química.

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Magnetic Bead/Gold Nanoparticle Double-Labeled Primers for Electrochemical Detection of Isothermal Amplified Leishmania DNA
De La Escosura-Muñiz A., Baptista-Pires L., Serrano L., Altet L., Francino O., Sánchez A., Merkoçi A. Small; 12 (2): 205 - 213. 2016. 10.1002/smll.201502350. IF: 8.315

A novel methodology for the isothermal amplification of Leishmania DNA using labeled primers combined with the advantages of magnetic purification/preconcentration and the use of gold nanoparticle (AuNP) tags for the sensitive electrochemical detection of such amplified DNA is developed. Primers labeled with AuNPs and magnetic beads (MBs) are used for the first time for the isothermal amplification reaction, being the amplified product ready for the electrochemical detection. The electrocatalytic activity of the AuNP tags toward the hydrogen evolution reaction allows the rapid quantification of the DNA on screen-printed carbon electrodes. Amplified products from the blood of dogs with Leishmania (positive samples) are discriminated from those of healthy dogs (blank samples). Quantitative studies demonstrate that the optimized method allows us to detect less than one parasite per microliter of blood (8 × 10-3 parasites in the isothermal amplification reaction). This pioneering approach is much more sensitive than traditional methods based on real-time polymerase chain reaction (PCR), and is also more rapid, cheap, and user-friendly. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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Microfluidic platform for environmental contaminants sensing and degradation based on boron-doped diamond electrodes
Medina-Sánchez M., Mayorga-Martinez C.C., Watanabe T., Ivandini T.A., Honda Y., Pino F., Nakata A., Fujishima A., Einaga Y., Merkoçi A. Biosensors and Bioelectronics; 75: 365 - 374. 2016. 10.1016/j.bios.2015.08.058. IF: 7.476

We have developed a lab-on-a-chip (LOC) platform for electrochemical detection and degradation of the pesticide atrazine (Atz). It is based on boron-doped diamond (BDD) electrodes and a competitive magneto-enzyme immunoassay (EIA) that enables high sensitivity. To detect the enzymatic reaction, we employed a BDD electrode modified with platinum nanoparticles (PtNPs), as a highly conductive catalytic transducer. Chronoamperometry revealed a limit of detection (LOD) of 3.5pM for atrazine, which, to the best of our knowledge, is one of the lowest value published to date. Finally, we degraded Atz in the same platform, using a bare BDD electrode that features remarkable corrosion stability, a wide potential window, and much higher O2 overvoltage as compared to conventional electrodes. These characteristics enable the electrode to produce a greater amount of HO• on the anode surface than do conventional electrodes and consequently, to destroy the pollutant more rapidly. Our new LOC platform might prove interesting as a smart system for detection and remediation of diverse pesticides and other contaminants. © 2015 Elsevier B.V.

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Modulation of population density and size of silver nanoparticles embedded in bacterial cellulose: Via ammonia exposure: Visual detection of volatile compounds in a piece of plasmonic nanopaper
Heli B., Morales-Narváez E., Golmohammadi H., Ajji A., Merkoçi A. Nanoscale; 8 (15): 7984 - 7991. 2016. 10.1039/c6nr00537c. IF: 7.760

The localized surface plasmon resonance exhibited by noble metal nanoparticles can be sensitively tuned by varying their size and interparticle distances. We report that corrosive vapour (ammonia) exposure dramatically reduces the population density of silver nanoparticles (AgNPs) embedded within bacterial cellulose, leading to a larger distance between the remaining nanoparticles and a decrease in the UV-Vis absorbance associated with the AgNP plasmonic properties. We also found that the size distribution of AgNPs embedded in bacterial cellulose undergoes a reduction in the presence of volatile compounds released during food spoilage, modulating the studied nanoplasmonic properties. In fact, such a plasmonic nanopaper exhibits a change in colour from amber to light amber upon the explored corrosive vapour exposure and from amber to a grey or taupe colour upon fish or meat spoilage exposure. These phenomena are proposed as a simple visual detection of volatile compounds in a flexible, transparent, permeable and stable single-use nanoplasmonic membrane, which opens the way to innovative approaches and capabilities in gas sensing and smart packaging. © 2016 The Royal Society of Chemistry.

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Molecularly Imprinted Polymer-Decorated Magnetite Nanoparticles for Selective Sulfonamide Detection
Zamora-Gálvez A., Ait-Lahcen A., Mercante L.A., Morales-Narváez E., Amine A., Merkoçi A. Analytical Chemistry; 88 (7): 3578 - 3584. 2016. 10.1021/acs.analchem.5b04092. IF: 5.886

Sulfonamides are known not only to be antimicrobial drugs that lead to antimicrobial resistance but also to be chemotherapeutic agents that may be allergenic and potentially carcinogenic, which represents a potentially hazardous compound once present in soil or water. Herein, a hybrid material based on molecularly imprinted polymer (MIP)-decorated magnetite nanoparticles for specific and label-free sulfonamide detection is reported. The composite has been characterized using different spectroscopic and imaging techniques. The magnetic properties of the composite are used to separate, preconcentrate, and manipulate the analyte which is selectively captured by the MIP onto the surface of the composite. Screen printed electrodes have been employed to monitor the impedance levels of the whole material, which is related to the amount of the captured analyte, via electrochemical impedance spectroscopy. This composite-based sensing system exhibits an extraordinary limit of detection of 1 × 10-12 mol L-1 (2.8 × 10-4 ppb) (S/N = 3), which is close to those obtained with liquid chromatography and mass spectrometry, and it was demonstrated to screen sulfamethoxazole in a complex matrix such as seawater, where according to the literature sulfonamides content is minimum compared with other environmental samples. © 2016 American Chemical Society.

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Nanochannels for electrical biosensing
de la Escosura-Muñiz A., Merkoçi A. TrAC - Trends in Analytical Chemistry; 79: 134 - 150. 2016. 10.1016/j.trac.2015.12.003. IF: 7.487

This review shows the recent trends on the use of both single and array nanochannels for electrical biosensing applications. Some general considerations on the principles of the stochastic sensing, together with an overview about the common routes for nanochannels preparation before focusing on the applications for DNA, protein, virus, toxin and other analytes detection are given. Emerging materials used to obtain nanochannels, such as graphene and its analogues as well as novel systems based on the use of nanoparticles in combination with nanochannels are discussed. Aspects related to the analytical performance of the developed devices are also discussed. Finally prospects for future improvements and applications of this technology are included. © 2015 Elsevier B.V.

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Paper-based sensors and assays: A success of the engineering design and the convergence of knowledge areas
López-Marzo A.M., Merkoçi A. Lab on a Chip - Miniaturisation for Chemistry and Biology; 16 (17): 3150 - 3176. 2016. 10.1039/c6lc00737f. IF: 5.586

This review shows the recent advances and state of the art in paper-based analytical devices (PADs) through the analysis of their integration with microfluidics and LOC micro- and nanotechnologies, electrochemical/optical detection and electronic devices as the convergence of various knowledge areas. The important role of the paper design/architecture in the improvement of the performance of sensor devices is discussed. The discussion is fundamentally based on μPADs as the new generation of paper-based (bio)sensors. Data about the scientific publication ranking of PADs, illustrating their increase as an experimental research topic in the past years, are supplied. In addition, an analysis of the simultaneous evolution of PADs in academic lab research and industrial commercialization highlighting the parallelism of the technological transfer from academia to industry is displayed. A general overview of the market behaviour, the leading industries in the sector and their commercialized devices is given. Finally, personal opinions of the authors about future perspectives and tendencies in the design and fabrication technology of PADs are disclosed. © 2016 The Royal Society of Chemistry.

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Water activated graphene oxide transfer using wax printed membranes for fast patterning of a touch sensitive device
Baptista-Pires L., Mayorga-Martínez C.C., Medina-Sánchez M., Montón H., Merkoçi A. ACS Nano; 10 (1): 853 - 860. 2016. 10.1021/acsnano.5b05963. IF: 13.334

We demonstrate a graphene oxide printing technology using wax printed membranes for the fast patterning and water activation transfer using pressure based mechanisms. The wax printed membranes have 50 μm resolution, longtime stability and infinite shaping capability. The use of these membranes complemented with the vacuum filtration of graphene oxide provides the control over the thickness. Our demonstration provides a solvent free methodology for printing graphene oxide devices in all shapes and all substrates using the roll-toroll automatized mechanism present in the wax printing machine. Graphene oxide was transferred over a wide variety of substrates as textile or PET in between others. Finally, we developed a touch switch sensing device integrated in a LED electronic circuit. © 2015 American Chemical Society.

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2015

A DNA aptasensor for electrochemical detection of vascular endothelial growth factor
Ravalli A., Rivas L., De La Escosura-Muñiz A., Pons J., Merkoçi A., Marrazza G. Journal of Nanoscience and Nanotechnology; 15 (5): 3411 - 3416. 2015. 10.1166/jnn.2015.10037.

Electrochemical aptasensors can detect different cancer biomarkers to provide point-of-care diagnosis that is low cost, rapid, specific and sensitive. In this work, we described the development of an electrochemical single-use aptasensor for detection and analysis of vascular endothelial growth factor (VEGF). Gold nanostructured graphite screen-printed electrodes were firstly modified with a mixed monolayer of a primary thiolated DNA aptamer and a spacer thiol, 6-mercapto-1-hexanol. VEGF protein was then incubated with the aptasensor. An enzyme-amplified detection scheme, based on the coupling of a streptavidin-alkaline phosphatase conjugate and secondary biotinylated aptamer was then applied. The enzyme catalyzed the hydrolysis of the electroinactive 1-naphthylphosphate to 1-naphthol; this product is electroactive and has been detected by means of differential pulse voltammetry (DPV). The aptasensor response was found to be linearly related to the target concentration between 0 and 250 nmol L-1 ; The detection limit was 30 nmol L-1 . The performance of the immunoassay in terms of reproducibility and selectivity has been also studied. © 2015 American Scientific Publishers All rights reserved.

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Alzheimer's disease biomarkers detection in human samples by efficient capturing through porous magnetic microspheres and labelling with electrocatalytic gold nanoparticles
de la Escosura-Muñiz A., Plichta Z., Horák D., Merkoçi A. Biosensors and Bioelectronics; 67: 162 - 169. 2015. 10.1016/j.bios.2014.07.086. IF: 6.409

A nanobiosensor based on the use of porous magnetic microspheres (PMM) as efficient capturing/pre-concentrating platform is presented for detection of Alzheimer's disease (AD) biomarkers. These PMMs prepared by a multistep swelling polymerization combined with iron oxide precipitation afford carboxyl functional groups suitable for immobilization of antibodies on the particle surface allowing an enhanced efficiency in the capturing of AD biomarkers from human serum samples. The AD biomarkers signaling is produced by gold nanoparticle (AuNP) tags monitored through their electrocatalytic effect towards hydrogen evolution reaction (HER). Novel properties of PMMs in terms of high functionality and high active area available for enhanced catalytic activity of the captured AuNPs electrocatalytic tags are exploited for the first time. A thorough characterization by scanning transmission electron microscope in high angle annular dark field mode (STEM-HAADF) demonstrates the enhanced ability of PMMs to capture a higher quantity of analyte and consequently of electrocatalytic label, when compared with commercially available microspheres. The optimized and characterized PMMs are also applied for the first time for the detection of beta amyloid and ApoE at clinical relevant levels in cerebrospinal fluid (CSF), serum and plasma samples of patients suffering from AD. © 2014 Elsevier B.V.

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An iridium oxide nanoparticle and polythionine thin film based platform for sensitive Leishmania DNA detection
Mayorga-Martinez C.C., Chamorro-García A., Serrano L., Rivas L., Quesada-Gonzalez D., Altet L., Francino O., Sánchez A., Merkoçi A. Journal of Materials Chemistry B; 3 (26): 5166 - 5171. 2015. 10.1039/c5tb00545k. IF: 4.726

An impedimetric label-free genosensor for high sensitive DNA detection is developed. This system is based on a screen-printed carbon electrode modified with the thionine layer and iridium oxide nanoparticles (IrO2 NP). An aminated oligonucleotide probe is immobilized on the IrO2 NP/polythionine modified electrode and ethanolamine was used as a blocking agent. Different diluted PCR amplified DNA samples have been detected. The selectivity and reproducibility of this system are studied and the system was highly reproducible with RSD ≈ 15% and sensitive enough while using 2% of ethanolamine during the blocking step employed for genosensor preparation. © The Royal Society of Chemistry.

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Annexin-V/quantum dot probes for multimodal apoptosis monitoring in living cells: Improving bioanalysis using electrochemistry
Montón H., Parolo C., Aranda-Ramos A., Merkoçi A., Nogués C. Nanoscale; 7 (9): 4097 - 4104. 2015. 10.1039/c4nr07191c. IF: 7.394

There is a great demand to develop novel techniques that allow useful and complete monitoring of apoptosis, which is a key factor of several diseases and a target for drug development. Here, we present the use of a novel dual electrochemical/optical label for the detection and study of apoptosis. We combined the specificity of Annexin-V for phosphatidylserine, a phospholipid expressed in the outer membrane of apoptotic cells, with the optical and electrochemical properties of quantum dots to create a more efficient label. Using this conjugate we addressed three important issues: (i) we made the labeling of apoptotic cells faster (30 min) and easier; (ii) we fully characterized the samples by common cell biological techniques (confocal laser scanning microscopy, scanning electron microscopy and flow cytometry); and (III) we developed a fast, cheap and quantitative electrochemical detection method for apoptotic cells with results in full agreement with those obtained by flow cytometry. This journal is © The Royal Society of Chemistry.

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Antithyroid drug detection using an enzyme cascade blocking in a nanoparticle-based lab-on-a-chip system
Kurbanoglu S., Mayorga-Martinez C.C., Medina-Sánchez M., Rivas L., Ozkan S.A., Merkoçi A. Biosensors and Bioelectronics; 67: 670 - 676. 2015. 10.1016/j.bios.2014.10.014. IF: 6.409

A methimazole (MT) biosensor based on a nanocomposite of magnetic nanoparticles (MNPs) functionalized with iridium oxide nanoparticles (IrOx NPs) and tyrosinase (Tyr) immobilized onto screen printed electrode (SPE) by using a permanent magnet is presented. This system is evaluated in batch mode via chelating copper at the active site of tyrosinase and in flow mode by thioquinone formation. The MT detection in flow mode is achieved using a hybrid polydimethylsiloxane/polyester amperometric lab-on-a-chip (LOC) microsystem with an integrated SPE. Both systems are very sensitive with low limit of detection (LOD): 0.006. μM and 0.004. μM for batch and flow modes, respectively. Nevertheless, the flow mode has advantages such as its reusability, automation, low sample volume (6. μL), and fast response (20. s). Optimization and validation parameters such as enzyme-substrate amount, flow rate, inhibition conditions, repeatability and reproducibility of the biosensor have been performed. The proposed methods have been applied in MT detection in spiked human serum and pharmaceutical dosage forms. © 2014 Elsevier B.V.

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Bismuth nanoparticles integration into heavy metal electrochemical stripping sensor
Cadevall M., Ros J., Merkoçi A. Electrophoresis; 36 (16): 1872 - 1879. 2015. 10.1002/elps.201400609. IF: 3.028

Between their many applications bismuth nanoparticles (BiNPs) are showing interest as pre-concentrators in heavy metals detection while being applied as working electrode modifiers used in electrochemical stripping analysis. From the different reported methods to synthesize BiNPs we are focused on the typical polyol method, largely used in these types of metallic and semi-metallic nanoparticles. This study presents the strategy for an easy control of the shape and size of BiNPs including nanocubes, nanosferes and triangular nanostructures. To improve the BiNP size and shape, different reducing agents (ethylene glycol or sodium hypophosphite) and stabilizers (polyvinyl pyrrolidone, PVP, in different amounts) have been studied. The efficiency of BiNPs for heavy metals analysis in terms of detection sensitivity while being used as modifiers of screen-printed carbon electrodes including the applicability of the developed device in real sea water samples is shown. A parallel study between the obtained nanoparticles and their performance in heavy metal sensing has been described in this communication. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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Eco-friendly electrochemical lab-on-paper for heavy metal detection
Medina-Sánchez M., Cadevall M., Ros J., Merkoçi A. Analytical and Bioanalytical Chemistry; 2015. 10.1007/s00216-015-9022-6. IF: 3.436

A disposable electrochemical lateral flow paper-based sensing device for heavy metal detection is proposed. The quantification of lead and cadmium in aqueous samples is demonstrated in a range from 10 to 100 ppb with a limit of detection of 7 and 11 ppb respectively. Moreover, the platform itself, which is made of paper, served as a sample pretreatment material due to its filtering properties. Real samples, especially in which the matrix is usually turbid and would in principle need a previous filtration, are successfully analyzed. This lab-on-paper device is simple, low cost, easy to fabricate, and portable, being a promising tool for new point-of-care applications in environmental monitoring, public health, and food safety. © 2015 Springer-Verlag Berlin Heidelberg

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Electrochemical Genosensors
Pérez-López B., Merkoçi A. Agricultural and Food Electroanalysis; : 295 - 316. 2015. 10.1002/9781118684030.ch10.

DNA biosensors, also called genosensors, are devices that are based on the immobilization of a single-stranded (ss) oligonucleotide probe onto a transducer surface that recognize-by hybridization-its complementary target sequence. In the case of electrochemical genosensors, the binding of the surface-confined probe and its complementary target strand is translated into a useful electrical signal. Electrochemical genosensors have advantages such as the use in many cases of simple, small, and portable equipment easy to be operated even by nonprofessional users. Besides the possibility to be miniaturized, these devices are usually of a low cost offering at the same time measurements with high sensitivity and specificity. In this chapter, a general description of DNA and nanomaterial-based detection systems is given. Several detection methods based, for example, on label-free formats and utilizing electrochemical and/or surface electroactivity of various platforms or direct methods relaying on the intrinsic electrochemical properties of DNA (the oxidation of purine bases, particularly guanine) are also given for applications in various fields including overall food quality and security. Copyright © 2015 John Wiley & Sons, Ltd. All rights reserved.

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Electrochemical Impedance Spectroscopy (bio)sensing through hydrogen evolution reaction induced by gold nanoparticles
Mayorga-Martinez C.C., Chamorro-Garcia A., Merkoçi A. Biosensors and Bioelectronics; 67: 53 - 58. 2015. 10.1016/j.bios.2014.05.066. IF: 6.409

A new gold nanoparticle (AuNP) based detection strategy using Electrochemical Impedance Spectroscopy (EIS) through hydrogen evolution reaction (HER) is proposed. This EIS-HER method is used as an alternative to the conventional EIS based on [Fe(CN)6]3-/4- or [Ru(NH3)6]3+/2+ indicators. The proposed method is based on the HER induced by AuNPs. EIS measurements for different amounts of AuNP are registered and the charge transfer resistance (Rct) was found to correlate and be useful for their quantification. Moreover the effect of AuNP size on electrical properties of AuNPs for HER using this sensitive technique has been investigated. Different EIS-HER signals generated in the presence of AuNPs of different sizes (2, 5, 10, 15, 20, and 50nm) are observed, being the corresponding phenomena extendible to other nanoparticles and related catalytic reactions. This EIS-HER sensing technology is applied to a magneto-immunosandwich assay for the detection of a model protein (IgG) achieving improvements of the analytical performance in terms of a wide linear range (2-500ngmL-1) with a good limit of detection (LOD) of 0.31ngmL-1 and high sensitivity. Moreover, with this methodology a reduction of one order of magnitude in the LOD for IgG detection, compared with a chroamperometric technique normally used was achieved. © 2014 Elsevier B.V.

View abstract
Graphene quantum dots-based photoluminescent sensor: A multifunctional composite for pesticide detection
Zor E., Morales-Narváez E., Zamora-Gálvez A., Bingol H., Ersoz M., Merkoçi A. ACS Applied Materials and Interfaces; 7 (36): 20272 - 20279. 2015. 10.1021/acsami.5b05838. IF: 6.723

Due to their size and difficulty to obtain, cost/effective biological or synthetic receptors (e.g., antibodies or aptamers, respectively), organic toxic compounds (e.g., less than 1 kDa) are generally challenging to detect using simple platforms such as biosensors. This study reports on the synthesis and characterization of a novel multifunctional composite material, magnetic silica beads/graphene quantum dots/molecularly imprinted polypyrrole (mSGP). mSGP is engineered to specifically and effectively capture and signal small molecules due to the synergy among chemical, magnetic, and optical properties combined with molecular imprinting of tributyltin (291 Da), a hazardous compound, selected as a model analyte. Magnetic and selective properties of the mSGP composite can be exploited to capture and preconcentrate the analyte onto its surface, and its photoluminescent graphene quantum dots, which are quenched upon analyte recognition, are used to interrogate the presence of the contaminant. This multifunctional material enables a rapid, simple and sensitive platform for small molecule detection, even in complex mediums such as seawater, without any sample treatment. © 2015 American Chemical Society.

View abstract
Highly sensitive and rapid determination of Escherichia coli O157: H7 in minced beef and water using electrocatalytic gold nanoparticle tags
Hassan A.R.H.A.A., de la Escosura-Muñiz A., Merkoçi A. Biosensors and Bioelectronics; 67: 511 - 515. 2015. 10.1016/j.bios.2014.09.019. IF: 6.409

A simple, highly sensitive and specific immunosensing assay for rapid detection and quantification of Escherichia coli O157:H7 in meat and water samples based on the electrocatalytic properties of gold nanoparticles (AuNPs) towards hydrogen evolution reaction and superparamagnetic microbeads (MBs) as pre-concentration/purification platforms without the need of broth enrichment is developed for the first time. Minced beef and water samples inoculated with different concentrations of E. coli O157:H7 have been tested using anti-E. coli O157-magnetic beads conjugate (MBs-pECAb) as a capture platform and sandwiching afterwards with AuNPs modified with secondary antibodies (AuNPs-sECAb) and detected using chronoamperometric measurement with screen-printed carbon electrodes (SPCEs). Detection limits (LOD) of 148, 457 and 309CFU/mL were obtained in buffer solution, minced beef and tap water samples respectively, with a broad detection range of 102-105CFU/mL in all cases. Recoveries percentages after spiking of 5 different samples of both minced beef and tap water with 103 and 104CFU/mL were 94.7 and 90.4 (in beef) and 91.3 and 94.8% (in water), respectively. Specificity, reproducibility and comparison with a commercial lateral flow kit in terms of LOD and detection range were also studied showing clear advantages of the electrochemical method performance. The successful application of this AuNPs based technology in minced beef and tap water indicates the possibility of its using in various food items and other water resources. © 2014 Elsevier B.V.

View abstract
In situ production of biofunctionalized few-layer defect-free microsheets of graphene
Gravagnuolo A.M., Morales-Narváez E., Longobardi S., Da Silva E.T., Giardina P., Merkoçi A. Advanced Functional Materials; 25 (18): 2771 - 2779. 2015. 10.1002/adfm.201500016. IF: 11.805

Biological interfacing of graphene has become crucial to improve its biocompatibility, dispersability, and selectivity. However, biofunctionalization of graphene without yielding defects in its sp2-carbon lattice is a major challenge. Here, a process is set out for biofunctionalized defect-free graphene synthesis through the liquid phase ultrasonic exfoliation of raw graphitic material assisted by the self-assembling fungal hydrophobin Vmh2. This protein (extracted from the edible fungus Pleurotus ostreatus) is endowed with peculiar physicochemical properties, exceptional stability, and versatility. The unique properties of Vmh2 and, above all, its superior hydrophobicity, and stability allow to obtain a highly concentrated (≈440-510 μg mL-1) and stable exfoliated material (ζ-potential, +40/+70 mV). In addition controlled centrifugation enables the selection of biofunctionalized few-layer defect-free micrographene flakes, as assessed by Raman spectroscopy, atomic force microscopy, scanning electron microscopy, and electrophoretic mobility. This biofunctionalized product represents a high value added material for the emerging applications of graphene in the biotechnological field such as sensing, nanomedicine, and bioelectronics technologies. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

View abstract
Lab-in-a-syringe using gold nanoparticles for rapid immunosensing of protein biomarkers
Nunes Pauli G.E., De La Escosura-Muñiz A., Parolo C., Helmuth Bechtold I., Merkoçi A. Lab on a Chip; 15 (2): 399 - 405. 2015. 10.1039/c4lc01123f.

We have developed a paper and gold nanoparticle (AuNP)-based lab-in-a-syringe (LIS) for immunosensing of biomarkers. This simple diagnostic device features simultaneous sampling and vertical-flow operation, which means that unlike typical immunosensors, it does not suffer from any delay between sampling and detection. It can handle large-volume, low-concentration samples for analysis in diverse applications (e.g. biomedical, environmental, food, etc.). Furthermore, its operating range for sample concentration can be tuned by simply changing the volume of the syringed sample, which enables on-demand limits of detection (LOD). The LIS contains two nitrocellulose pads: the conjugate pad (which captures the analyte) and the detection pad (which signals the presence of the captured analyte) both embedded into reusable plastic cartridges. We demonstrated its efficiency in detecting human IgG (HIgG) (LOD: 1.0 ng mL-1) and prostate-specific antigen (PSA) (spiked urine samples; LOD: 1.9 ng mL-1). In the field, the LIS can be used for complete on-site analysis or to obtain partially analyzed samples (AuNPs with captured analyte) for subsequent detailed testing in specialized laboratories. This journal is © The Royal Society of Chemistry 2015.

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Label-free impedimetric aptasensor for ochratoxin-A detection using iridium oxide nanoparticles
Rivas L., Mayorga-Martinez C.C., Quesada-González D., Zamora-Gálvez A., De La Escosura-Muñiz A., Merkoçi A. Analytical Chemistry; 87 (10): 5167 - 5172. 2015. 10.1021/acs.analchem.5b00890. IF: 5.636

In this article, a novel aptasensor for ochratoxin A (OTA) detection based on a screen-printed carbon electrode (SPCE) modified with polythionine (PTH) and iridium oxide nanoparticles (IrO2 NPs) is presented. The electrotransducer surface is modified with an electropolymerized film of PTH followed by the assembly of IrO2 NPs on which the aminated aptamer selective to OTA is exchanged with the citrate ions surrounding IrO2 NPs via electrostatic interactions with the same surface. Electrochemical impedance spectroscopy (EIS) in the presence of the [Fe(CN)6]-3/-4 redox probe is employed to characterize each step in the aptasensor assay and also for label-free detection of OTA in a range between 0.01 and 100 nM, obtaining one of the lowest limits of detection reported so far for label-free impedimetric detection of OTA (14 pM; 5.65 ng/kg). The reported system also exhibits a high reproducibility, a good performance with a white wine sample, and an excellent specificity against another toxin present in such sample. © 2015 American Chemical Society.

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Magnetic enzymatic platform for organophosphate pesticide detection using boron-doped diamond electrodes
Pino F., Ivandini T.A., Nakata K., Fujishima A., Merkoçi A., Einaga Y. Analytical Sciences; 31 (10): 1061 - 1068. 2015. 10.2116/analsci.31.1061.

A simple and reliable enzymatic system for organophosporus pesticide detection was successfully developed, by exploiting the synergy between the magnetic beads collection capacity and the outstanding electrochemistry property of boron-doped diamond electrodes. The determination of an organophosphate pesticide, chlorpyrifos (CPF), was performed based on the inhibition system of the enzyme acetylcholinesterase bonded to magnetic beads through a biotin-streptavidin complex system. A better sensitivity was found for a system with magnetic beads in the concentration range of 10 -9 to 10 -5 M. The estimated limits of detection based on IC 10 (10% acetylcholinesterase (AChE) inhibition) have been detected and optimized to be 5.7 × 10 -10 M CPF. Spiked samples of water of Yokohama (Japan) have been measured to validate the efficiency of the enzymatic system. The results suggested that the use of magnetic beads to immobilize biomolecules or biosensing agents is suitable to maintain the superiority of BDD electrodes. © 2015 The Japan Society for Analytical Chemistry.

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Micro and nanomotors in diagnostics
Chałupniak A., Morales-Narváez E., Merkoçi A. Advanced Drug Delivery Reviews; 95: 104 - 116. 2015. 10.1016/j.addr.2015.09.004. IF: 15.038

Synthetic micro/nanomotors are tiny devices than can be self-propelled or externally powered in the liquid phase by different types of energy source including but not limited to: catalytic, magnetic or acoustic. Showing a myriad of mechanical movements, building block materials, sizes, shapes and propulsion mechanisms micro/nanomotors are amenable to diagnostics and therapeutics. Herein we describe the most relevant micro/nanomotors, their fabrication pathways, propulsion strategies as well as in vivo and in vitro applications related with oligonucleotides, proteins, cells and tissues. We also discuss the main challenges in these applications such as the influence of complex media and toxicity issues as well as future perspectives. © 2015 Elsevier B.V.

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Nanochannel array device operating through Prussian blue nanoparticles for sensitive label-free immunodetection of a cancer biomarker
Espinoza-Castañeda M., Escosura-Muñiz A.D.L., Chamorro A., Torres C.D., Merkoçi A. Biosensors and Bioelectronics; 67: 107 - 114. 2015. 10.1016/j.bios.2014.07.039. IF: 6.409

A novel nanochannel array (NC) device that operates through Prussian blue nanoparticles (PBNPs) as redox indicator for sensitive label free immunodetection of a cancer biomarker is presented. Stable and narrow-sized (around 4nm) PBNPs, protected by polyvinylpyrrolidone, exhibited a well-defined and reproducible redox behavior and were successfully applied for the voltammetric evaluation of the nanochannels (20nm pore sized) blockage due to the immunocomplex formation. The bigger size of the PBNPs compared with ionic indicators such as the [Fe(CN)6]4-/3- system leads to an increase in the steric effects hindering their diffusion toward the signaling electrode which in turn is transduced to an improvement of the detection limit from 200μgmL-1 to 34pg human IgGmL-1. This novel and effective PBNPs-NC technology for the detection of small proteins captured inside the nanochannels is successfully applied for the quantification of a cancer biomarker (parathyroid hormone-related protein, PTHrP) in a real clinical scenario such as cell culture medium. The achieved label-free detection of PTHrP at levels of 50ngmL-1 is with great interest to study relevant functions that this protein exerts in normal tissues and cancer. © 2014 Elsevier B.V.

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Nanopaper as an Optical Sensing Platform
Morales-Narváez E., Golmohammadi H., Naghdi T., Yousefi H., Kostiv U., Horák D., Pourreza N., Merkoçi A. ACS Nano; 9 (7): 7296 - 7305. 2015. 10.1021/acsnano.5b03097. IF: 12.881

Bacterial cellulose nanopaper (BC) is a multifunctional material known for numerous desirable properties: sustainability, biocompatibility, biodegradability, optical transparency, thermal properties, flexibility, high mechanical strength, hydrophilicity, high porosity, broad chemical-modification capabilities and high surface area. Herein, we report various nanopaper-based optical sensing platforms and describe how they can be tuned, using nanomaterials, to exhibit plasmonic or photoluminescent properties that can be exploited for sensing applications. We also describe several nanopaper configurations, including cuvettes, plates and spots that we printed or punched on BC. The platforms include a colorimetric-based sensor based on nanopaper containing embedded silver and gold nanoparticles; a photoluminescent-based sensor, comprising CdSe@ZnS quantum dots conjugated to nanopaper; and a potential up-conversion sensing platform constructed from nanopaper functionalized with NaYF4:Yb3+@Er3+&SiO2 nanoparticles. We have explored modulation of the plasmonic or photoluminescent properties of these platforms using various model biologically relevant analytes. Moreover, we prove that BC is and advantageous preconcentration platform that facilitates the analysis of small volumes of optically active materials ∼4 μ). We are confident that these platforms will pave the way to optical (bio)sensors or theranostic devices that are simple, transparent, flexible, disposable, lightweight, miniaturized and perhaps wearable. © 2015 American Chemical Society.

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Nanoparticle-based lateral flow biosensors
Quesada-González D., Merkoçi A. Biosensors and Bioelectronics; 73: 47 - 63. 2015. 10.1016/j.bios.2015.05.050. IF: 6.409

Lateral flow biosensors (LFBs) are paper-based devices which permit the performance of low-cost and fast diagnostics with good robustness, specificity, sensitivity and low limits of detection. The use of nanoparticles (NPs) as labels play an important role in the design and fabrication of a lateral flow strip (LFS). The choice of NPs and the corresponding detection method directly affect the performance of these devices. This review discusses aspects related to the application of different nanomaterials (e.g. gold nanoparticles, carbon nanotubes, quantum dots, up-converting phosphor technologies, and latex beads, between others) in LFBs. Moreover, different detection methods (colorimetric, fluorescent, electrochemical, magnetic, etc.) and signal enhancement strategies (affording secondary reactions or modifying the architecture of the LFS) as well as the use of devices such as smartphones to mediate the response of LFSs will be analyzed. © 2015 Elsevier B.V.

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Nanoparticle/nanochannels-based electrochemical biosensors
Espinoza-Castañeda M., de la Escosura-Munñiz A., Merkoçi A. NanoScience and Technology; 96: 205 - 223. 2015. 10.1007/978-3-319-14406-1_9. IF: 0.000

The purpose of this chapter is to provide a general comprehensive overview on the latest trends in the development of nanoparticle/nanochannelsbased electrochemical biosensors. Given the importance of nanoparticles, some general considerations about their use in biosensors are given before focusing on nanochannels-based electrochemical biosensing systems. A detailed description of representative and recent works covering the main nanochannel arrays fabrication techniques and their application in electrochemical biosensing systems is also given. The combination of nanochannel array sensing capability with the known advantages of nanoparticles in immunosensing is shown as an ideal approach for the diagnostic of proteins and DNA. As conclusion, the integration of nanochannel arrays with electrochemical transducers (ex. screen-printed electrode) seems to be one of the most important challenges in the development of robust sensing devices that may bring electrochemical/nanochannel-based biosensing technology to the market. © Springer International Publishing Switzerland 2015.

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Nanoparticles-based nanochannels assembled on a plastic flexible substrate for label-free immunosensing
de la Escosura-Muñiz A., Espinoza-Castañeda M., Hasegawa M., Philippe L., Merkoçi A. Nano Research; 8 (4): 1180 - 1188. 2015. 10.1007/s12274-014-0598-5. IF: 7.010

A novel, cheap, disposable and single-use nanoparticles-based nanochannel platform assembled on a flexible substrate for label-free immunosensing is presented. This sensing platform is formed by the dip-coating of a homogeneous and assembled monolayer of carboxylated polystyrene nanospheres (PS, 200 and 500 nm-sized) onto the working area of flexible screen-printed indium tin oxide/polyethylene terephthalate (ITO/PET) electrodes. The spaces between the self-assembled nanospheres generate well-ordered nanochannels, with inter-PS particles distances of around 65 and 24 nm respectively. The formed nanochannels are used for the effective immobilization of antibodies and subsequent protein detection based on the monitoring of [Fe(CN)6]4− flow through diffusion and the decrease in the differential pulse voltammetric signal upon immunocomplex formation. The obtained sensing system is nanochannel-size dependent and allows human immunoglobulin G (IgG) (chosen as a model analyte) to be detected at levels of 580 ng/mL. The system also exhibits an excellent specificity against other proteins present in real samples and shows good performance with a human urine sample. The developed device represents an integrated and simple biodetection system which overcomes many of the limitations of previously reported nanochannels-based approaches and can be extended in the future to several other immuno and DNA detection systems. © 2014, Tsinghua University Press and Springer-Verlag Berlin Heidelberg.

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On-the-Spot Immobilization of Quantum Dots, Graphene Oxide, and Proteins via Hydrophobins
Gravagnuolo A.M., Morales-Narváez E., Matos C.R.S., Longobardi S., Giardina P., Merkoçi A. Advanced Functional Materials; 25 (38): 6084 - 6092. 2015. 10.1002/adfm.201502837. IF: 11.805

Class I hydrophobin Vmh2, a peculiar surface active and versatile fungal protein, is known to self-assemble into chemically stable amphiphilic films, to be able to change wettability of surfaces, and to strongly adsorb other proteins. Herein, a fast, highly homogeneous and efficient glass functionalization by spontaneous self-assembling of Vmh2 at liquid-solid interfaces is achieved (in 2 min). The Vmh2-coated glass slides are proven to immobilize not only proteins but also nanomaterials such as graphene oxide (GO) and quantum dots (QDs). As models, bovine serum albumin labeled with Alexa 555 fluorophore, anti-immunoglobulin G antibodies, and cadmium telluride QDs are patterned in a microarray fashion in order to demonstrate functionality, reproducibility, and versatility of the proposed substrate. Additionally, a GO layer is effectively and homogeneously self-assembled onto the studied functionalized surface. This approach offers a quick and simple alternative to immobilize nanomaterials and proteins, which is appealing for new bioanalytical and nanobioenabled applications. Immobilization of optically active nanomaterials and proteins (particularly, cadmium telluride quantum dots, graphene oxide, antibodies, and bovine serum albumin) on glass is achieved using a Janus-faced fungal protein, hydrophobin Vmh2, which is extracted from Pleurotus ostreatus. The proposed glass nanobiofunctionalization is fast, easily scalable, and environmental friendly, which is appealing for new bioanalytical and nanobioenabled applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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Photoluminescent Lateral-Flow Immunoassay Revealed by Graphene Oxide: Highly Sensitive Paper-Based Pathogen Detection
Morales-Narváez E., Naghdi T., Zor E., Merkoçi A. Analytical Chemistry; 87 (16): 8573 - 8577. 2015. 10.1021/acs.analchem.5b02383. IF: 5.636

A paper-based lateral flow immunoassay for pathogen detection that avoids the use of secondary antibodies and is revealed by the photoluminescence quenching ability of graphene oxide is reported. Escherichia coli has been selected as a model pathogen. The proposed device is able to display a highly specific and sensitive performance with a limit of detection of 10 CFU mL-1 in standard buffer and 100 CFU mL-1 in bottled water and milk. This low-cost disposable and easy-to-use device will prove valuable for portable and automated diagnostics applications. © 2015 American Chemical Society.

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Protein and DNA electrochemical sensing using anodized aluminum oxide nanochannel arrays
De La Escosura-Muniz A., Espinoza-Castaneda M., Merkoçi A. Springer Series in Materials Science; 219: 271 - 291. 2015. 10.1007/978-3-319-20334-8_9.

This chapter shows the recent trends on the use of anodized aluminum oxide (AAO) nanochannel arrays for electrochemical sensing of proteins and DNA with a special focus on those based on voltammetric detections. Some general considerations on nanochannels and especially on AAO nanoporous membranes are given first, followed by the receptors (antibody, DNA) immobilization as well as the set-up configuration. The typical optimization procedures as well as the detection principles ranging from the use of ionic electroactive indicators and nanoparticles (used also as blockers) are discussed. Aspects related to the analytical performance of the developed devices while applied in diagnostics including cancer biomarker detection are also given. Finally an overview for future improvements and applications of this technology are included. © Springer International Publishing Switzerland 2015.

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Triple lines gold nanoparticle-based lateral flow assay for enhanced and simultaneous detection of Leishmania DNA and endogenous control
Rivas L., de la Escosura-Muñiz A., Serrano L., Altet L., Francino O., Sánchez A., Merkoçi A. Nano Research; 8 (11): 3704 - 3714. 2015. 10.1007/s12274-015-0870-3. IF: 7.010

A novel triple lines lateral-flow assay (LFA) with enhanced sensitivity for the detection of Leishmania infantum DNA in dog blood samples was designed and successfully applied. The enhanced LFA methodology takes advantage of the gold nanoparticle tags (AuNPs) conjugated to polyclonal secondary antibodies, which recognize anti-FITC antibodies. The polyclonal nature of the secondary antibodies allows for multiple binding to primary antibodies, leading to enhanced AuNP plasmonics signal. Furthermore, endogenous control consisting of the amplified dog 18S rRNA gene was introduced to avoid false negatives. Using this strategy, 0.038 spiked Leishmania parasites per DNA amplification reaction (1 parasite/100 μL of DNA sample) were detected. Detection limit of LFA was found to be lower than that of the conventional techniques. In summary, our novel LFA design is a universal and simple sensing alternative that can be extended to several other biosensing scenarios. [Figure not available: see fulltext.] © 2015, Tsinghua University Press and Springer-Verlag Berlin Heidelberg.

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2014

Electrochemical antibody-aptamer assay for VEGF cancer biomarker detection
Ravalli A.; Marrazza G.; Rivas L.; De La Escosura-Muniz A.; Merkoci A. Lecture Notes in Electrical Engineering; 268 LNEE: 175 - 178. 2014. . IF: 0.000
Electrochemical antibody-aptamer assay for VEGF cancer biomarker detection
Ravalli A., Marrazza G., Rivas L., De La Escosura-Muniz A., Merkoci A. Lecture Notes in Electrical Engineering; 268 LNEE: 175 - 178. 2014. 10.1007/978-3-319-00684-0_33.

In this work, a simple and sensitive approach for VEGF detection using antibody-aptamer assay and gold screen-printed electrodes as transducers is presented. The assay was performed in a sandwich format. Anti-VEGF antibody was first chemically immobilized on the gold working electrode surface of screen-printed cell. After the incubation with the antigen, the sandwich assay was realized by incubation step with biotinylated anti-VEGF aptamer. The sensor was then incubated with streptavidin-alkaline phosphatase and with 1-naphthyl phosphate. Differential pulse voltammetry (DPV) measurements were performed to detect VEGF biomarker. © 2014 Springer International Publishing Switzerland.

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Electrochemical DNA sensors based on nanoparticles
Parolo C., De La Escosura-Muñiz A., Merkoçi A. Electrochemical Biosensors; : 195 - 222. 2014. .

[No abstract available]

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Graphene: Insights of its Application in Electrochemical Biosensors for Environmental Monitoring
Álvarez-Romero G.A., Alarcon-Angeles G., Merkoçi A. Biosensors Nanotechnology; 9781118773512: 111 - 140. 2014. 10.1002/9781118773826.ch5.

Due to their advantages over common analytical techniques, interest in using electrochemical sensors for monitoring chemical species of environmental interest has risen in recent years. Nanomaterials for electrochemical sensing have proved to be very useful in the development of novel tools for environment pollution monitoring. Graphene (GR), in particular, has been recognized as a promising material for the modification of electrodes used as (bio)sensors due to its unique chemical, physical and mechanical properties. Selectivity and/or specificity of (bio)sensors has been improved using electrodes modified with various receptors. In literature, there has been reported some scientific research towards electrochemical sensors based on GR, which makes these devices promising for monitoring environmental contaminants such as heavy metals, pesticides, phenol compounds, among others. In this chapter we describe the advances on the construction of electrochemical (bio)sensors based on GR for the monitoring of chemical compounds of environmental interest. © 2014 Scrivener Publishing LLC. All rights reserved.

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Lateral Flow Biosensors Based on Gold Nanoparticles
Rivas L., de la Escosura-Muñiz A., Pons J., Merkoçi A. Comprehensive Analytical Chemistry; 66: 569 - 605. 2014. 10.1016/B978-0-444-63285-2.00014-6.

The aim of these authors is to offer to the reader the general basis of lateral flow technology and overall of that based on the use of gold nanoparticles, its design, and various useful analytical applications. The historical progress of this technology discussed first is followed by a detailed description of the basic principles, formats, and components including its advantages and limitation. The use of gold nanoparticles as unique labels and their application for detection of different analytes such as proteins, DNA, mycotoxins, pesticides, and heavy metal detection is thoroughly detailed. Finally, new trends on lateral flow technology involving the use of new strategies and materials for improving its sensitivity are also presented and discussed. © 2014 Elsevier B.V.

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Simple on-plastic/paper inkjet-printed solid-state Ag/AgCl pseudoreference electrode
Da Silva E.T.S.G., Miserere S., Kubota L.T., Merkoçi A. Analytical Chemistry; 86 (21): 10531 - 10534. 2014. 10.1021/ac503029q.

A miniaturized, disposable, and low cost Ag/AgCl pseudoreference electrode based on inkjet printing has been developed. Silver ink was printed and chlorinated with bleach solution. The reference electrodes obtained in this work showed good reproducibility and stability during at least 30 min continuous measurement and even after 30 days storage without special care. Moreover, the strategy used in this work can be useful for large scale production of a solid-state Ag/AgCl pseudoreference electrode with different designs and sizes, facilitating the coupling with different electrical/electrochemical microsensors and biosensors. © 2014 American Chemical Society.

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