Thiolated DAB Dendrimers-Gold Nanoparticles as Self-Assembled Layers for the Direct Electrochemistry of HRP

Abstract

In this work, three generations of a thiolated DAB dendrimer have been used as bonding-layer between electrodeposited and colloidal gold nanoparticles of several sizes to develop electrocatalytic self-assembled layers for the covalent immobilization and direct electrochemistry of horseradish peroxidase (HRP). This study covers the kinetic, electrochemical and analytical characterization of all the prepared biosensors with the aim of developing the best electrocatalytic basis for future oxidase-peroxidase bienzymatic biosensors or biosensors based on the HRP inhibition. The best results were obtained with the dendrimer of third generation and 16 nm colloidal gold nanoparticles, which showed a homogeneous electron transfer rate constant of 422 s−1. This self-assembled monolayer was the most efficient to contact with the HRP active centre and allowed to determine hydrogen peroxide at an applied potential −0.3 V in three linear ranges of 0.4-200; 200–700 and 700–4000 μM with high sensitivities of 590; 441 and 303 μA mM−1 cm−2 respectively, low detection limit of 20 nM and fast response. The obtained apparent overall rate and Michaelis-Menten constants for this optimal biosensor were 0.047 A M−1 and 1.16 mM respectively. This last one, is significantly lower than the intrinsic K'M revealing the very high enzymatic efficiency of the developed devices.