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Abstract: We report a simple approach for the selectively electrochemical sensing of cysteine (CySH) using β-MnO2 nanowires modified glassy carbon (GC) electrode via a direct and facile electrochemical co-deposition process with chitosan hydrogel. The electrode showed excellent electrocatalytic effect toward cysteine oxidation. A possible reaction mechanism related to the formation of surface complexes was proposed: the –SH group is the reacting group in the reaction between cysteine and MnO2, while the –NH2 group acts as an anchor to stabilize the surface complexes. The electrocatalytic behavior is further developed as a sensitive detection scheme for cysteine by amperometric measurement, which shows a large determination range of 0.5–630μM and a low detection limit of 70nM. Other nineteen amino acids in a 20-fold concentration do not interfere in the detection of cysteine. Furthermore, other biological species containing –SH group or Ssuch as glutathione, cystine, and bovine serum albumin (BSA), show no interferences because of steric hindrance and inactive S/ce:simple-para> [Copyright &y& Elsevier]

Abstract: In this paper, gold nanoparticle–thionine–reduced graphene oxide (GNP–THi–GR) nanocomposites were prepared to design a label-free immunosensor for the sensitive detection of carcinoembryonic antigen (CEA). The nanocomposites with good biocompatibility, excellent redox electrochemical activity and large surface area were coated onto the glassy carbon electrode (GCE) surface and then CEA antibody (anti-CEA) was immobilized on the electrode to construct the immunosensor. The morphologies and electrochemistry of the formed nanocomposites were investigated by using scanning electron microscopy (SEM), ultraviolet–visible (UV–vis) spectrometry, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). CV and differential pulse voltammetry (DPV) studies demonstrated that the formation of antibody–antigen complexes decreased the peak current of THi in the GNP–THi–GR nanocomposites. The decreased currents were proportional to the CEA concentration in the range of 10–500pg/mL with a detection limit of 4pg/mL. The proposed method was simple, fast and inexpensive for the determination of CEA at very low levels. [Copyright &y& Elsevier]

Abstract: Tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)3 2+)–Zirconia–Nafion composite modified glassy carbon disk electrode as a solid-state electrochemiluminescence (ECL) detector is successfully applied to an electrophoretic microchip system with a wall-jet configuration. Pharmaceuticals such as tramadol, lidocaine and ofloxacin were selected to characterize the performance of this microchip capillary electrophoresis (CE)–ECL detection system. Voltammetric and ECL behaviors of immobilized Ru(bpy)3 2+ were investigated in lidocaine system. Influences of the separation electric field to cyclic voltammograms (CVs) of the immobilized Ru(bpy)3 2+ were also investigated. Tramadol, lidocaine and ofloxacin can be baseline separated without any additives. The detection limits (S/N=3) were 2.5×10−5 molL−1 for tramadol, 5.0×10−6 molL−1 for lidocaine, 1.0×10−5 molL−1 for ofloxacin under the sample injection of picoliters, and the linear ranges were from 5.0×10−5 to 2.5×10−3 molL−1 for tramadol, 1.0×10−5 to 1.0×10−3 molL−1 for lidocaine, and 1.0×10−5 to 2.5×10−3 molL−1 for ofloxacin, respectively. [Copyright &y& Elsevier]