A microfluidic electrochemical device for high sensitivity biosensing: detection of nanomolar hydrogen peroxide.

We report herein a simple device for rapid biosensing consisting of a single microfluidic channel made from poly(dimethylsiloxane) (PDMS) coupled to an injector, and incorporating a biocatalytic sensing electrode, reference and counter electrodes. The sensing electrode was a gold wire coated with 5 nm glutathione-decorated gold nanoparticles (AuNPs). Sensitive detection of H(2)O(2) based on direct bioelectrocatalysis by horseradish peroxidase (HRP) was used for evaluation. HRP was covalently linked the glutathione-AuNPs. This electrode presented quasi-reversible cyclic voltammetry peaks at -0.01 V vs Ag/AgCl at pH 6.5 for the HRP heme Fe(III)/Fe(II) couple. Direct electrochemical activity of HRP was used to detect H(2)O(2) at high sensitivity with a detection limit of 5 nM in an unmediated system.