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Altres ajuts: ICN2 is funded by CERCA programme, Generalitat de Catalunya. A.R.-M. acknowledges Universitat Autonoma de Barcelona (UAB) for the possibility of performing this work inside the framework of Biotechnology PhD Programme. Introduction: Since the COVID-19 pandemic, some of the routine methods for clinical diagnosis of infectious diseases have become closer to the general population and terms like "PCR" (polymerase chain reaction) and "antigen rapid diagnostic test" (RDT) are not restricted only to the scientific community but now also commonly appear in everyday language. Given the emergency, the pandemic also raised awareness about supply politics and regulation of the market for diagnostic tests [e.g., Emergency Use Authorization (EUA) from the Food and Drug Administration (FDA); or the "Conformité Européenne" marking (CE marking) from the European Union, EU]. PCR and RDT are two major techniques currently used in clinical practice for diagnosis of diseases. On the one hand, PCR is a highly sensitive method, but it relies on expensive equipment and qualified personnel. On the other hand, rapid diagnostic tests, despite being less sensitive, are faster, cheaper, portable, and battery/instrument-free. In this review, we will discuss the advantages and disadvantages of rapid antigen tests and different nucleic acid amplification techniques (NAATs), such as PCR, both as in vitro diagnostic devices. To do so, our review explains the working principle of each method, classifies the different subtypes, and analyzes the impact that the introduction of isothermal amplification methods will have in the diagnostic field. In addition, this review gives an overview of the current available products in the market and the new trends generated as a result of combining the strengths of NAAT and RDT.

Significant levels of infectious diseases caused by pathogenic bacteria are nowadays a worldwide matter, carrying considerable public health care challenges and huge economic concerns. Because of the rapid transmission of these biothreat agents and the outbreak of diseases, a rapid detection of pathogens in early stages is crucial, particularly in low-resources settings. To this aim, we developed for the first time a new sensing approach carried out in a single step for Escherichia coli O157:H7 detection. The detection principle is based on Förster resonance energy transfer using gold nanoclusters as a signal reporter and gold nanoparticles conjugated with antibodies as a quencher. The sensing platform includes an ultraviolet-light-emitting diode to provide the proper excitation and consists of a microtube containing two pieces of fiber glass; one of them is embedded with label-free gold nanoclusters and the other one with gold nanoparticles conjugated with antibodies. Upon the addition of the sample containing bacteria, the florescence of gold nanoclusters is recovered. The assay was evaluated by the naked eye (on/off) and quantitatively with use of a smartphone camera. The biosensor proved to be highly specific and sensitive, achieving a limit of detection as low as 4.0 cfu mL–1. Additionally, recoveries of 110% and 95% were obtained when the platforms in spiked river and tap water, respectively, were evaluated., The ICN2 is funded by the CERCA Programme/Generalitat de Catalunya. The ICN2 is supported by the Severo Ochoa program of the Spanish Ministry of Economy, Industry and Competitiveness (MINECO, gGrant No. SEV-2017-0706). Financial support was obtained under the MINECO Project MAT2017-87202-P. N.A. acknowledges the Food and Drug Laboratory Research Center, Food and Drug Organization of Iran, and Ministry of Science, Research and Technology of Iran for scholarships during this research time. A.S.T. acknowledges Universitat Autònoma de Barcelona for the possibility of carrying out this work inside the framework of its PhD Programme in Biotechnology.

The quantitative detection of different molecular targets is of utmost importance for a variety of human activities, ranging from healthcare to environmental studies. Bioanalytical methods have been developed to solve this and to achieve the quantification of multiple targets from small volume samples. Generally, they can be divided into two different classes: point of care (PoC) and laboratory-based approaches. The former is rapid, low-cost, and user-friendly; however, the majority of the tests are semiquantitative, lacking in specificity and sensitivity. On the contrary, laboratory-based approaches provide high sensitivity and specificity, but the bulkiness of experimental instruments and complicated protocols hamper their use in resource-limited settings. In response, here we propose a smartphone-based device able to support laboratory-based optical techniques directly at the point of care. Specifically, we designed and fabricated a portable microplate reader that supports colorimetric, fluorescence, luminescence, and turbidity analyses. To demonstrate the potential of the device, we characterized its analytical performance by detecting a variety of relevant molecular targets (ranging from antibodies, toxins, drugs, and classic fluorophore dyes) and we showed how the estimated results are comparable to those obtained from a commercial microplate reader. Thanks to its low cost (, ICN2 is funded by CERCA programme, Generalitat de Catalunya. Grant SEV-2017-0706 funded by MCIN/AEI/10.13039/501100011033. The authors acknowledge Consejo Superior de Investigaciones Científicas (CSIC) for the project “COVID19-122” granted in the call “Nuevas ayudas extraordinarias a proyectos de investigación en el marco de las medidas urgentes extraordinarias para hacer frente al impacto económico y social del COVID-19 (Ayudas CSIC-COVID-19)” and the research project INTCATCH 2020, Development and application of novel, integrated tools for monitoring and managing catchments supported by the European Union’s Horizon 2020 research and innovation program (Grant 689341). The authors also acknowledge the project MAT2017-87202-P funded by MCIN/AEI/10.13039/501100011033/and FEDER Una manera de hacer Europa. R.A.-D. acknowledges funding from the European Union Horizon2020 Programme under Grant No. 881603 (Graphene Flagship Core 3). A.I. was supported by PROBIST postdoctoral fellowship funded by the European Research Council (Marie Skłodowska-Curie grant agreement no. 754510).

The interaction of drugs with DNA has been searched thoroughly giving rise to an endless number of findings of undoubted importance, such as a prompt alert to harmful substances, ability to explain most of the biological mechanisms, or provision of important clues in targeted development of novel chemotherapeutics. The existence of some drugs that induce oxidative damage is an increasing point of concern as they can cause cellular death, aging, and are closely related to the development of many diseases. Because of a direct correlation between the response, strength/ nature of the interaction and the pharmaceutical action of DNA‐targeted drugs, the electrochemical analysis is based on the signals of DNA before and after the interaction with the DNA‐targeted drug. Nowadays, nanoscale materials are used extensively for offering fascinating characteristics that can be used in designing new strategies for drug‐DNA interaction detection. This work presents a review of nanomaterials (NMs) for the study of drug‐nucleic acid interaction. We summarize types of drug‐DNA interactions, electroanalytical techniques for evidencing these interactions and quantification of drug and/or DNA monitoring., The ICN2 is funded by the CERCA programme/Generalitat de Catalunya. ICN2 acknowledges the support of the Spanish MINECO for the Project MAT2017‐87202‐P and through the Severo Ochoa Centers of Excellence Program under Grant SEV2201320295. KDCM thank the CONACyT for the support through the scholarship #817447.

Solid-phase isothermal recombinase polymerase amplification (RPA) offers many benefits over the standard RPA in homogeneous phase in terms of sensitivity, portability, and versatility. However, RPA devices reported to date are limited by the need for heating sources to reach sensitive detection. With the aim of overcoming such limitation, we propose here a label-free highly integrated in situ RPA amplification/detection approach at room temperature that takes advantage of the high sensitivity offered by gold nanoparticle (AuNP)-modified sensing substrates and electrochemical impedance spectroscopic (EIS) detection. Plant disease (Citrus tristeza virus (CTV)) diagnostics was selected as a relevant target for demonstration of the proof-of-concept. RPA assay for amplification of the P20 gene (387-bp) characteristic of CTV was first designed/optimized and tested by standard gel electrophoresis analysis. The optimized RPA conditions were then transferred to the AuNP-modified electrode surface, previously modified with a thiolated forward primer. The in situ-amplified CTV target was investigated by EIS in a Fe(CN6)4–/Fe(CN6)3– red–ox system, being able to quantitatively detect 1000 fg μL–1 of nucleic acid. High selectivity against nonspecific gene sequences characteristic of potential interfering species such as Citrus psorosis virus (CPsV) and Citrus caxicia viroid (CCaV) was demonstrated. Good reproducibility (RSD of 8%) and long-term stability (up to 3 weeks) of the system were also obtained. Overall, with regard to sensitivity, cost, and portability, our approach exhibits better performance than RPA in homogeneous phase, also without the need of heating sources required in other solid-phase approaches., The ICN2 is funded by the CERCA programme/Generalitat de Catalunya. ICN2 acknowledges the support of the Spanish MINECO for the Project MAT2017-87202-P and the Severo Ochoa Centers of Excellence Program under Grant SEV2201320295. M.K. thanks Autonomous University of Barcelona for the opportunity of performing this work inside the framework of Biotechnology PhD Programme.

Point-of-care (PoC) tests are practical and effective diagnostic solutions for major clinical problems, ranging from the monitoring of a pandemic to recurrent or simple measurements. Although, in recent years, a great improvement in the analytical performance of such sensors has been observed, there is still a major issue that has not been properly solved: The ability to perform adequate sample treatments. The main reason is that normally sample treatments require complicated or long procedures not adequate for deployment at the PoC. In response, a sensing platform, called paperbased electrophoretic bioassay (PEB), that combines the key characteristics of a lateral flow assay (LFA) with the sample treatment capabilities of electrophoresis is developed. In particular, the ability of PEB to separate different types of particles and to detect human antibodies in untreated spiked whole blood is demonstrated. Finally, to make the platform suitable for PoC, PEB is coupled with a smartphone that controls the electrophoresis and reads the optical signal generated. It is believed that the PEB platform represents a much-needed solution for the detection of low target concentrations in complex media, solving one of the major limitations of LFA and opening opportunities for point-of-care sensors., We acknowledge financial support from the NACANCEL project PCIN-2016-066 (program Euronanomed 2). This work is also funded by the CERCA Program/Generalitat de Catalunya. The ICN2 is funded by the CERCA program/Generalitat de Catalunya. ICN2 acknowledges the support of the Spanish MINECO for the Project MAT2017-87202-P and through the Severo Ochoa Centers of Excellence Program under Grant SEV2201320295. R.A.-D. acknowledges the financial support from the EU Graphene Flagship Core 3 Project (No. 881603). A.S.-T. acknowledges the Autonomous University of Barcelona (UAB) for the possibility of performing this work inside the framework of Biotechnology Ph.D. Program. C.P. acknowledges Marie Skłodowska-Curie Actions Individual Fellowship, and this project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 795635. We also acknowledge Prof. Artur Xavier Roig from the Veterinary faculty in UAB for providing whole blood.

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., MINECO (Spain) for Project MAT2011-25870 is acknowledged.

Tristeza is one of the destructive diseases of citrus causing by citrus tristeza virus (CTV). Historically, CTV has been associated with serious outbreaks of quick decline of citrus, therefore CTV monitoring is important aspect for avoiding such re-emerging epidemics, which would threat citrus production through the world. In this context, we have designed for the first time a label-free impedimetric biosensor for the detection of nucleic acid of CTV. The sensing platform based on a screen-printed carbon electrode (SPCE) was modified by electrodeposited gold nanoparticles (AuNPs), which allowed to efficiently immobilizing thiolated ssDNA probes as well to enhance the electrode conductivity. The growth of AuNPs was optimized and characterized using scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). We investigated the behavior of thiolated ssDNA probe layer and its hybridization with target DNA onto AuNP surfaces by EIS measurements in Fe(CN6)4-/Fe(CN6)3- red-ox system. The main sensor design aspects such as AuNPs size, probe DNA concentration and immobilization time together with DNA hybridization time were optimized so as to achieve the best performance. Impedance values of DNA hybridization increased with Citrus tristeza-related synthetic DNA concentration, showing a logarithmic relation in the range of 0.1–10 μM. The results also indicate that the biosensor was able to selectively detect CTV nucleic acids in the presence of other non-specific DNAs. Moreover, we have demonstrated the good performance of the system in a real plant sample matrix. In addition, the sensor reproducibility enhanced after the hybridization onto MCH/poly (AT) thiolated DNA probes which was confirmed by intra- and inter-day variability assays., The ICN2 is funded by the CERCA programme/Generalitat de Catalunya. The ICN2 is supported by the Severo Ochoa programme of the Spanish Ministry of Economy, Industry and Competitiveness (MINECO, grant no. SEV-2013-0295). Mohga Khater thanks Autonomous University of Barcelona for the opportunity of performing this work inside the framework of Biotechnology PhD Programme.

Altres ajuts: the ICN2 is funded by the CERCA Programme/Generalitat de Catalunya. The development of paper-based electroanalytical strips as powerful diagnostic tools has gained a lot of attention within the sensor community. In particular, the detection of nucleic acids in complex matrices represents a trending topic, especially when focused toward the development of emerging technologies, such as liquid biopsy. DNA-based biosensors have been largely applied in this direction, and currently, there are two main approaches based on target/probe hybridization reported in the literature, namely Signal ON and Signal OFF. In this technical note, the two approaches are evaluated in combination with paper-based electrodes, using a single strand DNA relative to H1047R (A3140G) missense mutation in exon 20 in breast cancer as the model target. A detailed comparison among the analytical performances, detection protocol, and cost associated with the two systems is provided, highlighting the advantages and drawbacks depending on the application. The present work is aimed to a wide audience, particularly for those in the field of point-of-care, and it is intended to provide the know-how to manage with the design and development stages, and to optimize the platform for the sensing of nucleic acids using a paper-based detection method.

A new paper-based lateral flow immunoassay configuration was engineered and investigated. The assay is intended for the detection of a model protein in human serum, that is, human immunoglobulin G, with the aim to demonstrate a virtually universal protein detection platform. Once the sample is added in the strip, the analyte is selectively captured by antibody-decorated silica beads (Ab-SiO2) onto the conjugate pad and the sample flows by capillarity throughout the strip until reaching the test line, where a sandwich-like immunocomplex takes place due to the presence of antibody-functionalized QDs (Ab-QDs) onto the test line. Eventually, GO is added as a revealing agent and the photoluminescence of those sites protected by the complex Ab-SiO2/Antigen/Ab-QDs will not be quenched, whereas those photoluminescent sites directly exposed are expected to be quenched by GO, including the control line, made of bare QDs, reporting that the assay occurred successfully. Hence, the photoluminescence of the test line is modulated by the formation of sandwich-like immunocomplexes. The proposed device achieves a limit of detection (LOD) of 1.35 ng mL−1 in standard buffer, which is lower when compared with conventional lateral flow technology reported by gold nanoparticles, including other amplification strategies. Moreover, the resulting device was proven useful in human serum analysis, achieving a LOD of 6.30 ng mL−1 in this complex matrix. This low-cost disposable and easy-to-use device will prove valuable for portable and automated diagnostics applications, and can be easily transferred to other analytes such as clinically relevant protein biomarkers., This project was funded by the CERCA Programme / Generalitat de Catalunya. The Nanobiosensors and Bioelectronics Group acknowledges the support from the Generalitat de Catalunya (Grant 2014 SGR 260). ICN2 acknowledges support from the Severo Ochoa Program (MINECO, Grant SEV-2013-0295).

Finding fast and reliable ways to detect pathogenic bacteria is crucial for addressing serious public health issues in clinical, environmental, and food settings. Here, we present a novel assay based on the conversion of an electrochemical signal into a more convenient optical readout for the visual detection of Escherichia coli. Electropolymerizing polyaniline (PANI) on an indium tin oxide screen-printed electrode (ITO SPE), we achieved not only the desired electrochromic behavior but also a convenient way to modify the electrode surface with antibodies (taking advantage of the many amine groups of PANI). Applying a constant potential to the PANI-modified ITO SPE induces a change in their oxidation state, which in turn generates a color change on the electrode surface. The presence of E. coli on the electrode surface increases the resistance in the circuit affecting the PANI oxidation states, producing a different electrochromic response. Using this electrochromic sensor, we could measure concentrations of E. coli spanning 4 orders of magnitude with a limit of detection of 102 colony forming unit per 1 mL (CFU mL–1) by the naked eye and 101 CFU mL–1 using ImageJ software. In this work we show that merging the sensitivity of electrochemistry with the user-friendliness of an optical readout can generate a new and powerful class of biosensors, with potentially unlimited applications in a variety of fields., The ICN2 is funded by the CERCA Programme/Generalitat de Catalunya. The ICN2 is supported by the Severo Ochoa program of the Spanish Ministry of Economy, Industry and Competitiveness (MINECO, Grant SEV-2017-0706 and MAT2017-87202-P). C.P. acknowledges Marie Skłodowska-Curie Actions Individual Fellowship (Funding scheme, MSCA-IF-EF-RI; proposal number, 795635). The Iranian authors gratefully acknowledge the Research Council and the Center of Excellence for Nanostructures of the Sharif University of Technology, Tehran, Iran.

The authors describe a test stripe for fluorometric determination of the endocrine disruptor bisphenol A (BPA). Graphene quantum dots (GQDs) were immobilized on molecularly imprinted nanoparticles which then were placed on nitrocellulose paper. The GQDs display blue fluorescence (with excitation/emission peaks at 350/440 nm) which is reduced in the presence of BPA. The test stripe has a 43.9 ± 0.8 μg·L−1 limit of detection in case of water samples. The stripe was applied to the determination of BPA in (spiked) tap water and sea water, and the LODs were found to be 1.8 ± 0.2 μg·L−1 and 4.2 ± 0.5 μg·L−1, respectively. Structural analogs of BPA, such as aminophenol, phenol, hydroquinone and naphthol were found not to interfere., Recep Üzek thanks to TUBITAK for the given scholarship. We acknowledge support from MINECO, Spain for MAT2017-87202-P and Graphene Flagship Core Project 2 (Ref: 785219). ICN2 is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706). This work is also funded by the CERCA Programme / Generalitat de Catalunya.

A new class of nanomaterials called “2D materials” (2DMs) is attracting recently the electrochemical sensing field due to the unique physicochemical properties associated to their chemical structure, formed by ultra‐thin layers. In this review, we summarize the recent advances in the electroanalysis area using 2DMs giving first a brief overview on the structure, synthesis and properties of these materials followed by the analysis of their advantages while used in the development of electrochemical sensors., ICN2 acknowledges support from the Severo Ochoa Program (MINECO, Grant SEV-2013-0295).

Electrochromic effect and molecularly imprinted technology have been used to develop a sensitive and selective electrochromic sensor. The polymeric matrices obtained using the imprinting technology are robust molecular recognition elements and have the potential to mimic natural recognition entities with very high selectivity. The electrochromic behavior of iridium oxide nanoparticles (IrOx NPs) as physicochemical transducer together with a molecularly imprinted polymer (MIP) as recognition layer resulted in a fast and efficient translation of the detection event. The sensor was fabricated using screen-printing technology with indium tin oxide as a transparent working electrode; IrOx NPs where electrodeposited onto the electrode followed by thermal polymerization of polypyrrole in the presence of the analyte (chlorpyrifos). Two different approaches were used to detect and quantify the pesticide: direct visual detection and smartphone imaging. Application of different oxidation potentials for 10 s resulted in color changes directly related to the concentration of the analyte. For smartphone imaging, at fixed potential, the concentration of the analyte was dependent on the color intensity of the electrode. The electrochromic sensor detects a highly toxic compound (chlorpyrifos) with a 100 fM and 1 mM dynamic range. So far, to the best of our knowledge, this is the first work where an electrochromic MIP sensor uses the electrochromic properties of IrOx to detect a certain analyte with high selectivity and sensitivity., This work was supported by the European Commission Programme, H2020-WATER, INTCATCH Project (689341). This work is also funded by the CERCA Programme/Generalitat de Catalunya. ICN2 is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV2013-0295). R.A. acknowledges the financial support from CONACYT (Mexico).

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.

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.

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.

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 309 CFU/mL were obtained in buffer solution, minced beef and tap water samples respectively, with a broad detection range of 102–105 CFU/mL in all cases. Recoveries percentages after spiking of 5 different samples of both minced beef and tap water with 103 and 104 CFU/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.

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., This work was supported by TÜBİTAK (113Z664 and BİDEB-2214-A/1059B141400210) and was produced from a part of E. Zor's Ph.D. thesis. Nanobiosensors and Bioelectronics Group acknowledges the support from MINECO (Spain, MAT2014-52485-P and Severo Ochoa Program, Grant SEV-2013-0295) and Secretaria d′Universitats i Recerca del Departament d′Economia i Coneixement de la Generalitat de Catalunya (2014 SGR 260).

Mercury-based screen-printed electrodes (SPE) combined with square-wave anodic stripping voltammetry (SWASV) techniques for the analysis of copper, cadmium, lead, and zinc in different water samples have been applied. The detection system has been implemented in a flow cell and different experimental conditions have been tested in view of its application for in-situ monitoring. In particular, an acetate buffer together with a low chloride concentration (0.025 M NaCl) provided best performance and reproducible results. Additionally, the flow system was validated for the first time in terms of limits of detection, linearity, repeatability and recovery. Limits of detection of 2.8 μg L-1, 4.1 μg L-1, and 7.5 μg L-1 for cadmium, lead and copper respectively and repeatabilities lower than 10% (as RSD) were found. Good recoveries have been obtained for the three cations and in particular for copper, even in the presence of zinc. Finally, the method has shown its efficiency for the rapid screening of lead, cadmium and copper contained in both natural waters and wastewater samples. © 2013 Copyright Taylor and Francis Group, LLC., Financial support from CTQ2008-06847-C02-02/TECNO, MAT2008-03079/NAN and WARMER project (FP6-034472) are acknowledged.

This work is supported by theMICINN (Spain) grant for the Spain-Japan International Bilateral PIB2010JP-00278 project. A.L.M. thanks the Generalitat of Catalunya for the FI2010 predoctoral scholarship given. L.H. and J.L. thank the support of the Scientific Grant Agency VEGA of the Slovak Republic (Project 1/0182/11).

Selected Papers from the World Congress on Biosensors., A high sensitive voltammetric method for rapid determination of thrombin spiked in whole blood by taking advantage of both aptamer-based recognition and the use of a nanoporous membrane has been developed. The nanoporous membrane not only acts as platform for the thrombin recognition but also as filter of the micrometric components such as white and red blood cells, consequently minimizing matrix effects. The protocol involves a sandwich format in the inner walls (200nm diameter) of an anodized alumina oxide filter membrane (AAO). The analytical signal, by DPV oxidation of [Fe(CN) 6] 4-, is based on the blockage in the pores which affects the diffusion of [Fe(CN) 6] 4- to the screen-printed carbon electrotransducer (SPCEs) modified with the membrane. By labeling the anti-thrombin IgG with AuNPs followed by silver enhancement a greater passive signal enhancement in comparison to the membrane blockage has been observed. The contribution of both electrostatic/steric effects in this blockage due to the subsequent formation of the aptamer-thrombin complex and the final sandwich assay is investigated. The efficiency of the system is also monitored by microscopic techniques. The resulted biosensing system allows detecting thrombin spiked in whole blood at very low levels (LOD 1.8ngmL -1) which are within the range of clinical interest for the diagnostic of coagulation abnormalities as well as pulmonary metastasis. © 2012 Elsevier B.V., We acknowledge MICINN (Madrid) for the projects PIB2010JP-00278 and IT2009-0092, the E.U.'s support under FP7 contract number 246513“NADINE” and the NATO Science for Peace and Security Programme's support under the project SfP 983807. W.C. acknowledges a Ph.D. scholarship from the Royal Golden Jubilee Project of the Thailand Research Fund.

A disposable immunosensor for Salmonella enterica subsp. enterica serovar Typhimurium LT2 (S) detection using a magneto-immunoassay and gold nanoparticles (AuNPs) as label for electrochemical detection is developed. The immunosensor is based on the use of a screen-printed carbon electrode (SPCE) that incorporates a permanent magnet underneath. Salmonella containing samples (i.e. skimmed milk) have been tested by using anti-Salmonella magnetic beads (MBs-pSAb) as capture phase and sandwiching afterwards with AuNPs modified antibodies (sSAb-AuNPs) detected using differential pulse voltammetry (DPV). A detection limit of 143 cellsmL -1 and a linear range from 10 3 to 10 6 cellsmL -1 of Salmonella was obtained, with a coefficient of variation of about 2.4%. Recoveries of the sensor by spiking skimmed milk with different quantities of Salmonella of about 83% and 94% for 1.5×10 3 and 1.5×10 5 cellsmL -1 were obtained, respectively. This AuNPs detection technology combined with magnetic field application reports a limit of detection lower than the conventional commercial method carried out for comparison purposes in skimmed milk samples. © 2012 Elsevier B.V., We acknowledge MICINN (Madrid) for the projects PIB2010JP- 00278 and IT2009-0092, and the NATO Science for Peace and Security Programme's support under the project SfP 983807 and to the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Brasil for the scholarship given to André Santiago Afonso, grant number 200826/2011-5 and also Torres Quevedo scholarship given to Briza Pérez-López.

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 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., The authors acknowledge EU support under FP7-SME-2012–1 contract number 315653 “POC4PETS.” ICN2 also acknowledges the support of the Spanish MINECO under Project MAT2011–25870 and through the Severo Ochoa Centers of Excellence Program under Grant SEV-2013-0295, and the support from Secretaria d’Universitats i Recerca del Departament d’Economia i Coneixe-ment de la Generalitat de Catalunya (Grant 2014 SGR 260).

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 HO and bio-functionalization with glucose oxidase for glucose detection were achieved by the bioelectrode providing a proof for potential biosensing applications., ICN2 acknowledges support from the Severo Ochoa Program (MINECO, Grant SEV-2013-0295) and MICINN for the Project MAT2011–25870 and Generalitat de Cataluña for SGR support. The Ministry of Higher Education and Scientific Research of Tunisia (MHESR), the UTM University and the LCAE Laboratory are also acknowledged for research and travel funds granted for AR (LR99ES15).

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 mol L (2.8 × 10 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., This work was supported by The European Commission Program, FP7-OCEAN, SMS Project (613844). ICN2 acknowledges support from the Severo Ochoa Program (MINECO, Grant SEV-2013-0295). Nanobiosensors and Bioelectronics Group acknowledges Supramolecular NanoChemistry and Materials group (Dr. Carlos Carbonell and Prof. Daniel Maspoch at ICN2) for BET measurements, and the support from Secretaria d’Universitats i Recerca del Departament d’Economia i Coneixement de la Generalitat de Catalunya (2014 SGR 260). L.A.M acknowledges financial support from FAPESP-BEPE (2014/26088-4) project.

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., ICN2 acknowledges support from the Severo Ochoa Program (MINECO, Grant SEV-2013-0295). Authors wish to thank the Secretaria d'Universitats i Recerca del Departament d'Economia i Coneixement de la Generalitat de Catalunya for Grant 2014 SGR 260 support and the MHESR, University of Tunis El-Manar and the LCAE laboratory for research funds and mobility grant awarded to AMM. MEC (Spain) for MAT2011-25870 grant is also acknowledged.

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., We acknowledge the support of the Spanish MINECO under Project MAT2014-52485-P and through the Severo Ochoa Centers of Excellence Program under Grant SEV-2013-0295. The support from Secretaria d'Universitats i Recerca del Departament d'Economia i Coneixement de la Generalitat de Catalunya (Grant 2014 SGR 260) and from the E.C. under FP7-OCEAN 2013.1 contract number 613844 “SMS” are also acknowledged.

The performance of cadmium-selenide/zinc-sulfide (CdSe@ZnS) quantum dots (QDs) and the fluorescent dye Alexa 647 as reporter in an assay designed to detect apolipoprotein E (ApoE) has been compared. The assay is a sandwich immunocomplex microarray that functions via excitation by visible light. ApoE was chosen for its potential as a biomarker for Alzheimer's disease. The two versions of the microarray (QD or Alexa 647) were assessed under the same experimental conditions and then compared to a conventional enzyme-linked immunosorbent assay (ELISA) targeting ApoE. The QDs proved to be highly effective reporters in the microarrays, although their performance strongly varied in function of the excitation wavelength. At 633 nm, the QD microarray gave a limit of detection (LOD) of ~247 pg mL(-1); however, at an excitation wavelength of 532 nm, it provided a LOD of ~62 pg mL(-1), five times more sensitive than that of the Alexa microarray (~307 pg mL(-1)) and seven times more than that of the ELISA (~470 pg mL(-1)). Finally, serial dilutions from a human serum sample were assayed with high sensitivity and acceptable precision and accuracy.

Nanomaterials based sensing systems provide a new class of rapid and low cost detection alternatives with interest in the field of safety and security applications. In this review we report the recent trends in the use of various nanomaterials such as nanoparticles, carbon nanotubes, nanowires and graphene to detect different safety and security related analytes (i.e. microorganisms, toxins, pesticides and explosives). Nanomaterials are used either as modifiers of the electrochemical transducers or as labels with the objective to enhance the electrochemical signal, improve the stability and in general the performance of the detection systems including their cost-efficiency. Most of the developed systems are shown to bring excellent improvements while being used in the laboratory. Their application in real sample and during in-field monitoring still needs a long way while issues such as the reproducibility, stability, mass production capability of the designed devices etc. shouldn’t still yet be resolved.

Surface characterizations of mercury-coated screen-printed electrodes with interest for electrochemical stripping analysis of heavy metals detection are presented. SEM images and microanalysis data of the working electrode surface show a homogeneous distribution of mercury film prior to sensor application in heavy metals detection in seawater. The response stability during the 16 days measuring period in terms of RSD (relative standard deviation) was 33%, 24%, and 7.7% for Cd2+, Pb2+, and Cu2+, respectively. Detection limits lower than 7.0 μg L−1 in a seawater matrix modified with HCl are achieved for the three metals. The microscopic and microanalysis studies revealed some damages of the mercury film after a long period of use (continuous measuring) of the SPE. The decrease of the sensitivity as well as splitting of the peaks is related to the deposition and stripping of heavy metals in mixed mercury and “mercury free” areas. The application of this sensor for a longer period would need the use of a less...

A direct and simple inductively coupled plasma mass spectroscopy (ICP-MS) method for the determination of gold nanoparticles (AuNP) with different particle sizes ranging from 5 to 20 nm and suspended in aqueous solutions is described. The results show no significant difference compared to the determination of the same AuNPs after digestion, as claimed by the literature. The obtained limit of quantification of the method is 0.15 μg/L Au(III) that corresponds to 4.40 × 109 AuNP/L, considering spherical AuNPs 15 nm sized. Spike recovery experiments have shown that the sample matrix is a significant factor influencing the accuracy of the measurement. Spike recoveries from 93% to 95% are found for AuNP samples prepared in trisodium citrate, while for deionized H2O a spike recovery of around 80% was obtained. The sample preparation mode along with the ICP-MS parameters have been optimized and found to be crucial so as to achieve the required accuracy for the direct quantification of AuNP suspensions. The effect of the nanoparticle size upon the ICP-MS signal also was studied, and only significant differences due to the chemical environment and not to the AuNPs size were found.

Sensitive and stable monitoring of heavy metals in seawater using screen-printed electrodes (SPE) is presented. The analytical performance of SPE coupled with square wave anodic stripping voltammetry (SWASV) for the simultaneous determination of Pb and Cd in seawater samples, in the low microgL(-1) range, is evaluated. The stripping response for the heavy metals following 2min deposition was linear over the concentration range examined (10-2000microgL(-1)) with detection limits of 1.8 and 2.9microgL(-1) for Pb and Cd, respectively. The accuracy of the method was validated by analyzing metal contents in different spiked seawater samples and comparing these results to those obtained with the well-established anodic stripping voltammetry using the hanging mercury drop electrode. Moreover, a certified reference material was also used and the results obtained were satisfactory.

We give a general overview on the application of electrochemical analysis to biosensing using nanoparticles (NPs). We describe several examples of applications of voltammetric, potentiometric, conductometric, impedimetric and scanning electrochemical microscope-based methods in NP characterization, detection and quantification. We discuss these examples in terms of sensitivity and selectivity, and other parameters of analytical performance. Using bioassay applications, we discuss the advantages of direct (without previous dissolution) vs. indirect (after dissolution or enhancement) detection of NPs using both voltammetric and potentiometric techniques. In the final part of this review, we describe the use of scanning electrochemical microscopy in characterizing and investigating intrinsic properties of metal and semiconductor NPs. This technique offers a promising approach to future bioanalytical applications, especially for single-molecule detection. The reported electrochemical methods show clear advantages for DNA and protein detection when compared to other techniques, even though application to real samples and development of final market-oriented designs are still awaited.

A novel application of multiwall carbon nanotubes (MWCNT) for biosensor use is presented. β-Cyclodextrin (β-CD) as molecular receptor and MWCNT as enhancer of electron transfer are integrated in a dopamine (DA) electrochemical sensor system. The proposed molecular host–guest recognition based sensor has a high electrochemical sensitivity for the determination of DA. The electrochemical behaviour of DA is investigated by cyclic voltammetry (CV). The response mechanism of the MWCNT/β-CD modified electrode for DA is based on the combination of electrostatic and inclusion interaction of β-CD with DA which is distinguished from the response mechanism of non-modified electrode. The proposed integrated sensor showed improved analytical performance characteristics in catalytic oxidation of DA compared with non-modified electrode: excellent sensitivity, repeatability, stability, selectivity and recovery for the determination of DA. Under optimized conditions linear calibration plots were obtained for amperometric detection of DA over the range 0.01–0.08 mM.

Carbon nanotubes (CNTs) are offering a great promise for developing electrochemical sensors. Distinctive properties of CNTs such as a high surface area, ability to accumulate analyte, minimization of surface fouling and electrocatalytic activity are very attractive for electrochemical sensing. The electrochemical study of a glassy carbon (GC) electrode coated with a matrix based in multiwall carbon nanotubes (MWCNTs), tetrahydrofuran (THF) mixed with poly(vinyl chloride) (PVC) and with a glutaraldehyde (GA) solution (MWCNTs-TPG/GC), for β-Nicotinamide adenine dinucleotide (NADH) detection is discussed in this work using cyclic voltammetry (CV) and chronoamperometry. The used CNTs matrix promotes better the electron transfer of NADH minimizing the fouling effect. The obtained results show remarkable electrochemical and mechanical advantages of MWCNTs-TPG/GC electrode compared to bare glassy carbon electrode with a great promise for future amperometric biosensors applications.

A second generation glucose biosensor was developed by using neutral red (NR) as a mediator and a bismuth film electrode (BiFE) as a transducer along with immobilized glucose oxidase. The linear range was between 0.2 and 2.5 mM, and a correlation coefficient of 0.999 was obtained with this electrode. The standard deviation (at 1 mM glucose for n = 4) and the coefficient of variation were calculated as ±8.07 µM and 3.4%, respectively. The biosensor was used for the determination of glucose in wine samples.

The presented work includes the development of a microbial biosensor based on a carbon-nanotube epoxy composite (CNTEC) platform used as supporting electrode for cell immobilization. For this purpose, cells of Pseudomonas fluorescens were immobilized on the surface of the CNTEC electrode by means of gelatin which was then cross linked with glutaraldehyde. After optimization of experimental parameters like cell amount, pH and temperature, the system was calibrated for glucose. From the calibration graph the linear range was estimated as 0.5 – 4.0 mM with a response time of 100 s. Furthermore, substrate specificity and operational stability were investigated. Finally, the results that were obtained with CNTEC electrodes were compared with conventional graphite epoxy composite electrode (GECE) and as a result, higher current values (2 to 3 folds) were observed with CNTEC microbial biosensor.

The electrochemical properties of gold nanoparticles (AuNPs) have led to their widespread use as DNA labels. This fact has improved the design strategies for the electrochemical detection of DNA through hybridization event monitoring. The reported DNA hybridization detection modes are based on either AuNP detection after dissolving or the direct detection of the AuNP/DNA conjugates anchored onto the genosensor surface. Various enhancement strategies have been reported so as to improve the detection limit. Most are based on catalytic deposition of silver onto AuNP. Other strategies based on the use of AuNPs as carrier/amplifier of other labels will be also revised. The developed techniques are characterized by sensitivities and specificities that enable further applications of the developed DNA sensors in several fields.

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 IC10 (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.

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., This work was supported by MINECO, (Spain, BIO2013-49464-EXP). ICN2 acknowledges support from the Severo Ochoa Program (MINECO, Grant SEV-2013-0295).

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., The authors acknowledge support of the Spanish MINECO under Project MAT2011−25870 and through the Severo Ochoa Centers of Excellence Program under Grant SEV-2013-0295. L.R. also acknowledges Universitat Autònoma de Barcelona for her predoctoral grant

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 4 nm) PBNPs, protected by polyvinylpyrrolidone, exhibited a well-defined and reproducible redox behavior and were successfully applied for the voltammetric evaluation of the nanochannels (20 nm 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 200 µg mL−1 to 34 pg human IgG mL−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 50 ng mL−1 is with great interest to study relevant functions that this protein exerts in normal tissues and cancer., We acknowledge MINECO (Madrid) for the project MAT2011-25870, the EU's support under FP7 contract number 246513 “NADINE”. Marisol Espinoza-Castañeda acknowledges to Ministerio de Educación del Programa de Formación de Profesorado UniversitarioAP2010-5942. The authors also wish to thank Fundació Privada Cellex.

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., We acknowledge the E.U.’s support under FP7-SME-2012-1 contract number 315653 ‘‘POC4PETS’’. ICN2 also acknowledges support of the Spanish MINECO under Project MAT2011-25870 and through the Severo Ochoa Centers of Excellence Program under Grant SEV-2013-0295.

This report studies the electrochemical response of wall-jet detector for microchip electrophoresis (microCE). It shows that in wall-jet configuration, the electrochemical detector operates in coulometric mode and that there is an influence of detection potential upon peak width and therefore upon the resolution of solutes. Upon raising the detection potential from +0.3 to +0.9 V, the resolution between model analytes, dopamine and catechol, increases from 0.63 to 2.90. The reasons for this behavior originate in wall-jet detector design and in its typically significant higher detector volume than the volume of injected sample. The conversion efficiency of the wall-jet electrochemical detection cell was found to be 97.4% for dopamine and 98.0% for catechol. The paper brings deeper understanding of operations of wall-jet electrochemical detectors for microchip devices, and it explains previously reported significantly sharper peaks when electrocatalytic electrodes (i.e., palladium and carbon nanotube) were used in microCE-electrochemistry wall-jet detector.

The modification of a graphite–epoxy composite electrode (GECE) with bacterial cells along with an analytical application are presented. Pseudomonas putida DSM 50026 was used as a biological component and the measurement was based on the respiratory activity of the cells. The optimization of working conditions of resulting biosensor (including pH and temperature) was conducted and the limit of detection was calculated as 7 μM phenol based on the signal to noise ratio. Then the system was applied for xenobiotic detection. Resulting sample signals were found to be very similar with the standard solutions having the same concentration while the recoveries of the spiked samples were close to 100%.

This overview covers important aspects of microfluidic chip platforms as new materials for electrochemical (EC) sensing. It describes important trends in constructing detectors and their electronics on microfluidic chip platforms, the importance of selecting appropriate detector materials, and the different detection modes in on-chip amperometry, conductometry and potentiometry. We pay particular attention to the latest developments and to the fundamental issues of on-chip EC detection. We also discuss important applications of microfluidic chip platforms in genomic, security and environmental applications.

A new rigid graphite-epoxy composite electrode for electrochemical detection in microchip electrophoresis is described. The end-column wall-jet detection design relying on tubular rigid composite working electrode shows favorably low noise level and high signal-to-noise ratio when compared to glassy carbon detector. The performance of rigid graphite-epoxy composite detector was compared to glassy carbon detector using dopamine and catechol as model analytes. The various parameters of the microchip electrophoresis-rigid graphite-epoxy composite detector were optimized.

This work describes a voltammetric electronic tongue, in which the quantitative information contained in voltammograms obtained from amperometric sensors is firstly extracted employing the discrete wavelet transform (DWT) and then processed employing artificial neural networks (ANNs). The analytical case studied is the direct determination of the oxidizable aminoacids tryptophan, cysteine and tyrosine, and its application in the direct measurement of these amino acids in animal feed samples. A conventional voltammetry cell with a Pt working electrode is the experimental set-up and differential pulse voltammetry the selected technique. Due to the complexity of the obtained signals, the DWT pre-treatment was needed in order to eliminate noise components and compress voltammograms by selecting and extracting significant information. The ANN was subsequently used to model the system departing from the reduced information, and obtaining the concentrations of the considered species. Best results were obtained when using two hidden layers in a backpropagation neural network trained with the Bayesian regularization algorithm.

A new SWCNT modified gold detector for microchip capillary electrophoresis–electrochemistry is described. SWCNT modified gold electrode displays greatly improved sensitivity and separation resolution compared to bare gold electrode, reflecting the electrocatalytic activity of SWCNT. The SWCNT/Au electrode exhibits low background noise levels. Parameters such as separation voltage and detection potential of the microchip electrophoresis–electrochemistry with SWCNT modified gold electrode were optimized.