Amperometric hydrogen peroxide biosensor based on the immobilization of HRP on DNA–silver nanohybrids and PDDA-protected gold nanoparticles

A novel amperometric hydrogen peroxide biosensor based on the immobilization of horseradish peroxidase (HRP) on DNA–silver nanohybrids (DNA–Ag) and poly(diallyldimethylammonium chloride) (PDDA)-protected gold nanoparticles (PDDA–Au) was successfully fabricated by combining the self-assembly technique with an in situ electrochemical reduction of the DNA–Ag+ complex. The preparation process of modified electrode was characterized with UV–vis absorption spectroscopy, transmission electron microscopy (TEM) and atomic force microscope (AFM). The electrochemical characteristics of the biosensor were studied by cyclic voltammetry and chronoamperometry. Experimental conditions influencing the biosensor performance such as pH, potential were optimized. The resulting biosensor (HRP/DNA–Ag/PDDA–Au/DNA–Ag/Au electrode) showed a linear response to H2O2 over a concentration range from 7.0 μM to 7.8 mM with a detection limit of 2.0 μM (S/N = 3) under optimized conditions. The apparent Michaelis–Menten constant ( K M app ) was evaluated to be 1.3 mM. The sensor exhibited high sensitivity, good accuracy and an acceptable stability.