Direct electrochemistry of horseradish peroxidase immobilized on the layered calcium carbonate–gold nanoparticles inorganic hybrid composite

A mediator-free hydrogen peroxide (H2O2) biosensor was fabricated based on immobilization of horseradish peroxidase (HRP) on layered calcium carbonate–gold nanoparticles (CaCO3–AuNPs) inorganic hybrid composite. The proposed biosensor showed a strong electrocatalytic activity toward the reduction of H2O2, which could be attributed to the favored orientation of HRP in the well-confined surface as well as the high electrical conductivity of the resulting CaCO3–AuNPs inorganic hybrid composite. The hybrid composite was obtained by the adsorption of AuNPs onto the surfaces of layered CaCO3 through electrostatic interaction. The key analytical parameters relative to the biosensor performance such as pH and applied potential were optimized. The developed biosensor also exhibited a fast amperometric response (3 s), a good linear response toward H2O2 over a wide range of concentration from 5.0 × 10−7 to 5.2 × 10−3 M, and a low detection limit of 1.0 × 10−7 M. The facile, inexpensive and reliable sensing platform based on layered CaCO3–AuNPs inorganic hybrid composite should hold a huge potential for the fabrication of more other biosensors.