A novel electrochemical immunosensor based on hydrogen evolution inhibition by enzymatic copper deposition on platinum nanoparticle-modified electrode

A novel electrochemical immunosensor was developed based on enzymatic deposition of copper onto platinum (Pt) nanoparticle-modified electrode that inhibited the electrocatalytic reduction of protons to hydrogen in acidic medium by Pt. The method was implemented for the determination of a model target, human immunoglobulin G (hIgG), using a microtiter-based sandwiched immunoassay with alkaline phosphatase (ALP)-antibody conjugate as the detection probe. The binding of ALP on the microtiter interface due to the presence of target hIgG catalyzed the hydrolysis of a substrate ascorbic acid 2-phosphatase(AAP), producing a reductive product ascorbic acid that mediated the deposition of copper on a Pt nanoparticle-modified electrode. A negative shift of hydrogen evolution potential was thus obtained at the Pt nanoparticle-modified electrode, which could be determined using linear sweep voltammetry in 0.1 M HCl. The influence of experimental variables including the concentrations of HPtCl6, Cu2+, and AAP as well as the reaction time of enzymatic copper deposition upon the potential shift was investigated. Under optimized conditions, the potential shift was observed to show linear dependency on hIgG concentration over a range from 10 pg mL(-1) to 1.0 mu g mL(-1) with a readily achievable detection limit of 2.0 pg mL(-1). The developed method could be implemented with simple operation, high sensitivity and multiple-sample format, indicating that this technique might hold great promise in various environmental, food, and clinical applications. (C) 2008 Elsevier B.V. All rights reserved.