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 H2O2 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 FeIII/FeII couple. Direct electrochemical activity of HRP was used to detect H2O2 at high sensitivity with a detection limit of 5 nM in an unmediated system.