Search

A disposable amperometric immunosensor was studied for the rapid detection of carp (Carassius auratus) Vitellogenin (Vtg). The sensor was fabricated based on screen-printed carbon arrays (SPCAs) containing eight carbon working and an integrated carbon counter electrodes. To construct the sensor, a conducting polymer (poly-terthiophene carboxylic acid) was electropolymerized on the surface of working electrodes and the polymer-coated SPCAs was characterized by SEM. Horseradish peroxidase (HRP) and a monoclonal antibody (anti-Vtg) specific to carp Vtg were covalently attached onto the polymer modified SPCAs. The immobilization of HRP and anti-Vtg onto the polymer-coated SPCAs was examined using cyclic voltammetry and quartz crystal microbalance studies. In order to detect the amount of Vtg, glucose oxidase (GOx)-labelled Vtg bound to the sensor surface under competition with the Vtg analyte was quantified amperometrically using glucose as a substrate. The performance of the eight sensors in arrays was evaluated by obtaining the calibration plots for Vtg. The sensor arrays exhibit a linear range of the Vtg concentration from 0.25 to 7.8 ng/ml and the detection limit was determined to be 0.09 ng/ml. Furthermore, the performance of the immunosensor for the determination of Vtg was evaluated by a standard addition method performed in fish serum samples.

Abstract: A new approach for an amperometric array sensor platform employing arrays of sensors in a 24-well cell culture plate format has been developed for simultaneous in vitro determination of nitric oxide (NO) and superoxide free radicals (O2 −) produced by stimulated cells. The work reported focuses on the direct, real-time monitoring of extracellular production of these two analytes, as well as the effects of their interaction. The sensor platform was manufactured by a combination of sputtering gold electrodes and screen-printing carbon electrodes. The O2 − sensor uses covalent immobilization of cytochrome c via a binder, DTSSP (3,3′-dithio-bis(sulphosuccinimidylpropionate) onto the surface of the Au electrodes, whereas the NO sensor system involves an NiTSPc (nickel tetrasulfonated phthalocyanine) film electrodeposited onto the surface of the carbon electrodes and subsequently covered with an external layer of Nafion®. For in vitro demonstration of the platforms as a potential drug-screening system, A172 glioblastoma cells were cultured and transferred into the 24-well arrays. Simultaneous and direct monitoring of NO and O2 − production as a response to chemicals of biomedical relevance was carried out. The results obtained demonstrated that it would be possible to envisage a drug screening platform for compounds designed to be inhibitors of nitric oxide synthase or to have an inhibitory effect on superoxide free radical production. By suitable modification of the electrodes employed it would also be possible to extend the platform to measure alternative species. [Copyright &y& Elsevier]

Four electrode materials: Pt, Au, Pd and glassy carbon (GC), were studied to investigate their suitability as substrates in the development of two different classes of glutamate biosensor. Glutamate oxidase cross-linked onto poly(o-phenylenediamine) was chosen as the type 1 biosensor (PPD/GluOx), incorporating PPD as the permselective element to detect H2O2 directly on the electrode surface at relatively high applied potentials. GluOx and horseradish peroxidase/redox polymer modified electrodes (Os2+PVP/HRP/GluOx) that relied on enzyme-catalysed H2O2 detection at lower applied potentials were used as type 2 biosensors.The voltammetric and amperometric responses to the enzyme signal transduction molecule, H2O2, and the archetypal interference species in biological applications, ascorbic acid, were determined on the bare and PPD/GluOx-modified surfaces. The amperometric responses of these electrodes were stable over several days of continuous recording in phosphate buffered saline (pH 7.4). The sensitivity of the type 1 biosensors to H2O2 and glutamate showed parallel trends with low limits of detection and good linearity at low concentrations: Pt>Au∼Pd≫GC. Type 2 biosensors out-performed the type 1 design for all electrode substrates, except Pt. However, the presence of the permselective PPD membrane in the type 1 biosensors, not feasible in the type 2 design, suggests that Pt/PPD/GluOx might have the best all-round characteristics for glutamate detection in biological media containing interference species such as ascorbic acid. Other points affecting a final choice of substrate should include factors such as mass production issues. [Copyright &y& Elsevier]

A novel voltammetric sensor was developed to selectively determine dopamine (DA) concentration in the presence of ascorbic acid (AA) and 3,4-dihydroxyphenylacetic acid (DOPAC). This sensor utilizes a modified pencil graphite electrode (PGE) coated with a newly synthesized poly (3,4-ethylene dioxythiophene) (PEDOT):poly (styrene sulfonate- co -2-(3-(6-Methyl-4-oxo-1,4-dihydropyrimidin-2-yl) ureido) ethyl methacrylate) (P(SS- co -UPyMA)) composite. The PEDOT:P(SS-co-UPyMA) (PPU) composite was characterized using nuclear magnetic resonance, X-ray photoelectron, and Raman spectroscopies. The PPU-coated PGE was characterized using electrochemical techniques, including cyclic and differential pulse voltammetry. Compared to uncoated, PPU-coated PGE demonstrated improved sensitivity and selectivity for DA. The sensor exhibited a dynamic linear range of 0.1–300 μM for DA, with a detection limit of 44.4 nM (S/N = 3). Additionally, the PPU-coated PGE showed high reproducibility and storage stability for four weeks. To demonstrate its practical applicability, the PPU-coated PGE sensor was used for ex vivo brain slice samples from control and Parkinson's disease model mice. [Display omitted] • Disposable voltametric dopamine sensor based on modified pencil graphite electrode. • Newly synthesized PEDOT:PSS copolymer as electrode modifier. • The dopamine sensor showed a linear range: 0.1–300 μM & LOD: 44.4 nM. • The sensor was used on ex vivo brain samples from Parkinson's disease model mice. [ABSTRACT FROM AUTHOR]

[Display omitted] • A facile single-step method was used to prepare PATT film on ASPE surface. • PATT film was coated on the surface via stable amide linkage. • The prepared PATT@ASPE has a large surface area with excellent electrochemical properties. • PATT@ASPE was used for detecting Hg2+ in different fish muscle samples. Anodized screen-printed electrode (ASPE) was modified by electrochemical polymerization of 5-amino-4H-1,2,4-triazole-3-thiol (ATT) to form a poly-ATT (PATT) film for the selective and sensitive detection of Hg2+ ions by Anodic Stripping Voltammetry (ASV). The porous PATT film was uniformly coated on the surface through disulfide (S S) linkage, free N H, and amide bonds for binding preconcentrated Hg2+ ions. The prepared PATT@ASPE was characterized by cyclic voltammetry, Field-Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM) with Energy Dispersive X-ray spectroscopy (EDS) and Attenuated Total Reflection Infrared Spectroscopy (ATR-IR). Under optimized experimental conditions (0.1 M KCl as supporting electrolyte and preconcentration at –0.1 V for 120 s), PATT@ASPE was successfully used for detecting Hg2+. A linear relationship between the anodic peak current and [Hg2+] was achieved in the concentration range of 0.03 to 245 nM, with a limit of detection (S/N = 3) of 0.005 nM and a calculated sensitivity of 15.0085 µA nM−1 L-1 cm−2. Further, selective detection of Hg2+ was demonstrated in the presence of interfering species such as other heavy metal ions (Pb2+, Cd2+, Cu2+, etc.), organic molecules, other cations, and various anions. The electroanalytical performance of PATT@ASPE exhibited outstanding long-term stability and reproducibility. Finally, PATT@ASPE was successfully applied to measure Hg2+ in fish muscle samples, and the results were validated using inductively coupled plasma-mass spectrometry. [ABSTRACT FROM AUTHOR]