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In this work, we propose a potentiometric smart sensor for lithium detection in environmental samples based on a screen-printed cell. The graphite screen-printed electrode (GSPE) was first modified by gold and silver nanoparticles to increase the conductivity, and then by an ion-selective membrane, which was directly deposited onto the nanostructured electrode surface. The potentiometric cell, thanks to its small size, was integrated with a portable instrument connected to a smartphone for decentralized analysis. The developed sensor was used in drop- and microflow-configurations and showed a high sensitivity for lithium with a low detection limit (1.6 µM). It was also applied in the analysis of real samples from the industrial recycling of automotive batteries and complex matrices, such as contaminated soils. [ABSTRACT FROM AUTHOR]

In this work, an electrochemical DNA biosensor, based on a dual signal amplified strategy by employing a polyaniline film and gold nanoparticles as a sensor platform and enzyme-linked as a label, for sensitive detection is presented. Firstly, polyaniline film and gold nanoparticles were progressively grown on graphite screen-printed electrode surface via electropolymerization and electrochemical deposition, respectively. The sensor was characterized by scanning electron microscopy (SEM), cyclic voltammetry and impedance measurements. The polyaniline-gold nanocomposite modified electrodes were firstly modified with a mixed monolayer of a 17-mer thiol-tethered DNA probe and a spacer thiol, 6-mercapto-1-hexanol (MCH). An enzyme-amplified detection scheme, based on the coupling of a streptavidin-alkaline phosphatase conjugate and biotinylated target sequences was then applied. The enzyme catalyzed the hydrolysis of the electroinactive α-naphthyl phosphate to α-naphthol; this product is electroactive and has been detected by means of differential pulse voltammetry. In this way, the sensor coupled the unique electrical properties of polyaniline and gold nanoparticles (high surface area, fast heterogeneous electron transfer, chemical stability, and ease of miniaturisation) and enzymatic amplification. A linear response was obtained over a concentration range (0.2-10 nM). A detection limit of 0.1 nM was achieved. [ABSTRACT FROM AUTHOR]

The aim of this work is the preparation of DNA-sensing architectures based on gold nanoparticles (AuNPs) in conjunction with an enzyme-amplified detection to improve the analytical properties of genosensor. In order to assess the utility of study as DNA-sensing devices, a thiolated DNA capture probe sequence was immobilized on the gold nanoparticle modified surface. After labeling of the biotinylated hybrid with a streptavidin-alkaline phosphatase conjugate, the electrochemical detection of the enzymatic product was performed on the surface of a disposable electrode. Two different enzymatic substrates to detect the hybridization event were studied. In the first case, the enzyme catalyzed the hydrolysis of α-naphthyl phosphate; the product is electroactive and has been detected by means of differential pulse voltammetry (DPV). In the second one, the enzyme catalyzed the precipitation of an insoluble and insulating product on the sensing interface. In this case, the electrochemical transduction of the hybridization process was performed by electrochemical impedance spectroscopy (EIS). [ABSTRACT FROM AUTHOR]

In this paper, two simple and sensitive approaches for CA 125 detection are presented by using antibody immobilized on poly-anthranilic acid modified graphite screen-printed electrodes. The first proposed approach is a label-free impedimetric immunosensor. The immunoassay is based on poly-anthranilic acid (PAA) modified graphite screen-printed electrodes with subsequent covalently monoclonal antibody anti-CA 125 immobilization. The modified screen-printed electrodes are used to capture the protein from the sample solutions. A curve calibration by electrochemical impedance spectroscopy (EIS) was obtained. The second approach is based on a sandwich format. The monoclonal anti-CA 125 antibodies immobilized on poly-anthranilic acid modified graphite screen-printed electrodes is used to capture the protein from the sample solution. The sandwich assay is then performed by adding secondary anti-CA 125 antibodies labeled with gold nanoparticles (AuNPs). The antibody-AuNPs captured onto immunosensor surface induced the silver deposition from a silver enhancer solution. The deposited AgNPs could be measured by anodic stripping analysis (ASV) in acid solution. A curve calibration by ASV was obtained. The experimental conditions were examined and were optimized using electrochemical impedance spectroscopy. The performance of both immunosensors in terms of sensitivity, reproducibility and selectivity were studied. [ABSTRACT FROM AUTHOR]

Mercury is one of the most well‐known toxic contaminants of natural and anthropogenic origin in aquatic ecosystems that can bioaccumulate in vegetal and animal organisms. In this work, we propose a smart detection system for Hg(II) ions by square wave anodic stripping voltammetry at nanocomposite graphite screen‐printed electrodes, as an analytical tool to be applied in food quality control. The nanocomposite surfaces were obtained by the modification of screen‐printed graphite electrodes with poly(l‐aspartic acid) and gold nanoparticles and were characterized by means of electrochemical techniques. An exhaustive study of the experimental conditions involved both in the electropolymerization and in the voltammetric stripping measurements was addressed to develop a reliable method capable of measuring Hg(II) concentration in the low μg/L range, both in conventional and drop configurations. The sensor was integrated in a smart setup, comprising a Sensit Smart pocket instrument connected to a smartphone, thus proving its applicability for in situ analysis due to its cost‐effectiveness. The analytical significance of the developed sensor was assessed by detecting Hg(II) in novel food samples. [ABSTRACT FROM AUTHOR]

In this work, we report the development of a simple and sensitive sensor based on graphite screen-printed electrodes (GSPEs) modified by a nanocomposite film for dopamine (DA) detection. The sensor was realized by electrodepositing polyaniline (PANI) and gold nanoparticles (AuNPs) onto the graphite working electrode. The sensor surface was fully characterized by means of the cyclic voltammetry (CV) technique using [Fe(CN)6]4−/3− and [Ru(NH3)6]2+/3+ as redox probes. The electrochemical behavior of the nanocomposite sensor towards DA oxidation was assessed by differential pulse voltammetry (DPV) in phosphate buffer saline at physiological pH. The sensor response was found to be linearly related to DA concentration in the range 1–100 μM DA, with a limit of detection of 0.86 μM. The performance of the sensor in terms of reproducibility and selectivity was also studied. Finally, the sensor was successfully applied for a preliminary DA determination in human serum samples. [ABSTRACT FROM AUTHOR]

In this work, we report the design, the development and the characterization of the analytical performances of a colorimetric smartphone-based immunosensor for the detection of cancer antigen 125 (CA125). The immunosensor was based on a sandwich strategy in which the primary antibody was immobilized by spotting onto the 3D nitrocellulose membrane. The immunospots were subsequently incubated with CA125 solutions, followed by the affinity reaction with a secondary antibody labeled with gold nanoparticles (AuNPs). The antibody-AuNPs captured onto immunospots induced the silver deposition from a silver enhancer solution leading to the formation of gold-silver nanoparticles of different grey color spots depending on CA125 concentration. The 8 megapixels smartphone camera was integrated in a home-made dark box and used as transducer of color image acquisition and data handling. The pixel intensity of the captured images was determined by an image processing algorithm. The experimental parameters involved in each step of the immunosensor design were studied and optimized, obtaining a limit of detection of 30 U/mL CA125. The selectivity of the immunoassay was proven against different concentration solutions of Vascular Endothelial Growth Factor (VEGF) antigen as an unspecific protein when a blank signal was obtained for all tested solutions. Finally, preliminary experiments in human serum samples spiked with CA125 protein were also performed. Therefore, the proposed system could represent a powerful point-of-care tool for the next generation technology for detecting and monitoring cancer biomarkers at early stages by taking advantage of nowadays gadgets with enhanced features such as smartphones. [ABSTRACT FROM AUTHOR]

In this paper, we report the development of a sensitive label-free impedimetric biosensor based on the use of affibody as bioreceptor and gold nanostructured screen-printed graphite as a sensor platform for the detection of human epidermal growth factor receptor 2 (HER2). The affisensor is realized by immobilizing a terminal cysteine-modified affibody on gold nanoparticles. The sensor was characterized by electrochemical techniques and scanning electron microscopy (SEM). Furthermore, surface plasmon resonance (SPR) technology was also applied to explore the potential of affibodies as small-molecule discriminating tools. Using optimized experimental conditions, a single-use affisensor showed a good analytical performance for HER2 detection from 0 to 40 μg/L. The estimated limit of detection was 6.0 μg/L. Finally, the realized affisensor was applied to human serum samples. [ABSTRACT FROM AUTHOR]

• Aptamer/mycotoxin interaction investigated by docking study. • Realization of a disposable aptasensor. • Deoxynivalenol detection in useful environmental range. • Application to spiked food samples. This work proposes a voltammetric aptasensor to detect deoxynivalenol (DON) mycotoxin. The development steps of the aptasensor were partnered for the first time to a computational study to gain insights onto the molecular mechanisms involved into the interaction between a thiol-tethered DNA aptamer (80mer-SH) and DON. The exploited docking study allowed to find the binding region of the oligonucleotide sequence and to determine DON preferred orientation. A biotinylated oligonucleotide sequence (20mer-BIO) complementary to the aptamer was chosen to carry out a competitive format. Graphite screen-printed electrodes (GSPEs) were electrochemically modified with polyaniline and gold nanoparticles (AuNPs@PANI) by means of cyclic voltammetry (CV) and worked as a scaffold for the immobilization of the DNA aptamer. Solutions containing increasing concentrations of DON and a fixed amount of 20mer-BIO were dropped onto the aptasensor surface: the resulting hybrids were labeled with an alkaline phosphatase (ALP) conjugate to hydrolyze 1-naphthyl phosphate (1-NPP) substrate into 1-naphthol product, detected by differential pulse voltammetry (DPV). According to its competitive format, the aptasensor response was signal-off in the range 5.0–30.0 ng·mL−1 DON. A detection limit of 3.2 ng·mL−1 was achieved within a 1-hour detection time. Preliminary experiments on maize flour samples spiked with DON yielded good recovery values. [ABSTRACT FROM AUTHOR]