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In this work, a novel amperometric biosensor for the determination of adenosine triphosphate (ATP) was developed. The biosensor was based on two enzymes (glucose oxidase and hexokinase) that were entrapped in the electrospun nanofibers. The biosensor was prepared by direct electrospinning of the enzymes/polymer mixture on the surface of platinum disc electrodes with subsequent UV cross-linking of the obtained nanofibers. Photocrosslinkable polymer (polyvinyl alcohol containing styrylpyridinium groups, PVA-SbQ) was chosen as matrix, while gold nanoparticles (GNPs) were added to the enzymes/polymer mixture to improve analytical characteristics of the biosensor. For the first time, incorporation of several enzymes in the nanofibers during electrospinning was demonstrated. Composition of the mixture for electrospinning was optimized. The obtained biosensors enabled successful detection of ATP by chronoamperometry, linear range was 25–200 μM. The analytical characteristics of the biosensors were compared with the biosensors prepared by manual drop-casting of the enzymes/polymer/GNP mixture. The biosensor can be also used to detect glucose in samples with known or very low (< 10 μM) ATP concentration; linear range of the glucose determination was 0.01–3 mM. The described approach for one-step electrospinning of several enzymes is fast and simple and can be easily modified for immobilization of other multi-enzyme systems, which opens possibilities to enlarge the range of the targets that can be determined by the biosensors produced using electrospinning. [ABSTRACT FROM AUTHOR]

Polydiacetylene (PDA) inserted in films or in vesicles has received increasing attention due to its property to undergo a blue-to-red colorimetric transition along with a change from non-fluorescent to fluorescent upon application of various stimuli. In this review paper, the principle for the detection of various microorganisms (bacteria, directly detected or detected through the emitted toxins or through their DNA, and viruses) and of antibacterial and antiviral peptides based on these responsive PDA vesicles are detailed. The analytical performances obtained, when vesicles are in suspension or immobilized, are given and compared to those of the responsive vesicles mainly based on the vesicle encapsulation method. Many future challenges are then discussed. [ABSTRACT FROM AUTHOR]

Interleukin-8 (IL-8), a dimeric protein composed of two identical subunits, is overexpressed in different human cancers, among them pancreatic cancers and head and neck cancers. There is a strong demand for monitoring of this biomarker protein for early cancer detection. A new concept of label-free impedimetric immunosensors for IL-8 detection is described in this work. A nanocomposite of gold nanoparticles (AuNPs) decorating a magnetic Fe3O4 core is synthesized using cysteamine as linker, and characterized using TEM and UV-Vis spectrometry. After immobilization of these Fe3O4@Au magnetic nanocomposites on a boron doped diamond (BDD) electrode using a simple magnet, anti-human IL-8 monoclonal antibody is linked to the AuNPs, previously functionalized with thioctic acid. The functionalization of the immunosensor was characterized using two electrochemical techniques: cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), performed in phosphate buffer with ferro/ferricyanide as the redox probe. The EIS technique was used for affinity assays: antibody-Antigen binding. A linear relationship between the increment in the electron transfer resistance (RCT) and the logarithmic value of IL-8 concentration was observed between 0.1 pg/mL and 1000 pg/mL. The limit of detection (LOD) was estimated at 0.03 pg/mL. [ABSTRACT FROM AUTHOR]

Herein, we report the easy and rapid fabrication of water-stable electrospun nanofibers from blends of the photochemically crosslinkable polyvinyl alcohol styrylpyridinium polymer (PVA-SbQ), carboxylated multiwall carbon nanotubes (MWCNT-COOHs) and glucose oxidase (GOx) for electrochemical biosensor application. Different electrospinning parameters including flow rate, applied voltage, distance between tip and collector, polymer concentration and MWCNT-COOHs content in the electrospun solution were tailored to produce PVA-SbQ/MWCNT-COOH nanofibers with minimal beading and enhanced electrical properties. Optimal PVASbQ and MWCNT-COOHs concentrations were 6.7 wt% and 5 wt% with respect to the total solution and polymer mass, respectively. The nanofibers were rendered water insoluble via exposure to UV irradiation for 10 min. The electrochemical properties of electrospun PVA-SbQ/MWCNT-COOH nanofibrous mats were characterized by cyclic voltammetry and electrochemical impedance spectroscopy. Scanning electron microscopy and transmission electron microscopy were used to characterize the morphology of the nanofibers. GOx, used as model enzyme, was further incorporated into the PVA-SbQ/MWCNT-COOH mixture before electrospinning. The obtained biosensor enabled successful detection of glucose by cyclic voltammetry. The resulting novel glucose biosensor revealed very good storage and operational stabilities, a low limit of detection (2 μ M) and a wide linear range (up to at least 4 mM). [ABSTRACT FROM AUTHOR]

The aim of this study was to develop versatile diagnostic tools based on the use of innovative polythiolated probes for the detection of multiple viruses. This approach is compatible with optical enzyme-linked oligosorbent assay (ELOSA) or electrochemical (biosensors) detection methods. The application targeted here concerns the rapid genotypin g of Hepatitis C virus (HCV). HCV genotyping is one of the predictive parameters currently used to define the antiviral treatment strategy and is based on the sequencing of the viral NS5b region. Generic and specific NS5b amplicons were produced by real-time polymease chain reaction (RT-PCR) on HCV(+) human plasma. Original NS5b probes were designed for genotypes 1a/1b, 2a/2b/2c, 3a, and 4a/4d. Robust polythiolated probes were anchored with good efficacy on maleimide-activated microplates (MAM) and gold electrodes. Their grafting on MAM greatly increased the sensitivity of the ELOSA test which was able to detect HCV amplicons with good sensitivity (10 nM) and specificity. Moreover, the direct and real-time electrochemical detection by differential pulse voltammetry enabled a detection limit of 10 fM to be reached with good reproducibility. These innovative polythiolated probes have allowed us to envisage developing flexible, highly sensitive, and easy-to-handle platforms dedicated to the rapid screening and genotyping of a wide range of viral agents. [ABSTRACT FROM AUTHOR]