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Abstract: In this article, an electrochemically direct stripping approach based on silver nanoparticles (AgNPs) labeled with antibody was proposed. To prepare AgNPs labels, glutathione (GSH) was chemically absorbed on the surface of AgNPs through its free thiol groups. Glutaraldehyde was used as a coupling reagent, its two aldehyde groups reacted with the amino group of GSH absorbed on the AgNPs surfaces and the amino groups of antibodies, respectively. The resulting labeled electrochemical active nanoparticles could recognize the proteins specifically via the immobilized antibody. To prove the electrochemical property of labeled AgNPs, human IgG was used as a model protein sample to be immobilized on a screen printed electrode (SPE) and the goat-anti-human IgG labeled AgNPs was added onto the surface of the SPE, followed by differential pulse voltammetric (DPV) method. With the oxidation of AgNPs labels coupled on the electrodes, the concentration of hIgG could be assayed directly and calculated. The dynamic concentration was in the range of 1–1000ng/mL and the detection limit was 0.4ng/mL (S/N =3). In addition, the presented method was also compared to indirect electrochemical stripping detection by dissolving AgNPs labels with nitric acids and the results showed advantages such as lower detection limit, rapidity and simplicity. [Copyright &y& Elsevier]

Abstract: Gold nanofilm, with a nanoporous morphology, was found to have the unique property to catalyze the oxidization of ascorbic acid (AA) and dopamine (DA), resulting in the improved electrochemical behavior of the two species and a negative shift of the oxidization potential of AA for about 300mV. The catalytic oxidization of gold nanofilm to AA is mainly ascribed to its high surface energy, while the enhanced electron transfer ability of DA on the gold nanofilm is attributed to the strong interaction between DA and the electrode surface. Based on the peak separation of DA and AA, selective detection of DA was achieved on the gold nanofilm modified electrode. Differential pulse voltammetry (DPV) techniques and cyclic voltammetry (CV) were used to investigate the electrochemical behavior of AA and DA on the surface of the electrode. Afterwards, the obtained gold nanofilm was applied in selective detection of dopamine (DA) in the presence of ascorbic acid (AA) at near neutral pH by DPV in the optimized conditions. The linear range for DA was 1.5–27.5μM. The electrode also shows good stability during detection. [Copyright &y& Elsevier]