Porous Gold-Nanoparticle−CaCO₃ Hybrid Material:  Preparation, Characterization, and Application for Horseradish Peroxidase Assembly and Direct Electrochemistry

Gold nanoparticles (AuNPs) were assembled on the surface of porous calcium carbonate microspheres (CaCO 3 ) in a neutral aqueous solution through electrostatic interaction. The resulting gold-nanoparticle−CaCO 3 hybrid material (AuNP−CaCO 3 ) was characterized and expected to offer a promising template for enzyme immobilization and biosensor fabrication because of its satisfying biocompatibility and improved properties. It was conjugated with horseradish peroxidase (HRP) to fabricate HRP−AuNP−CaCO 3 bioconjugates, which were then embedded into a silica sol−gel matrix to construct a novel biosensor. Because of the synergic effect of CaCO 3 microspheres and AuNPs, direct electron transfer of HRP was observed at this biosensor. The biosensor exhibited a fast amperometric response to H 2 O 2, with a linear range of 4.0 × 10 - 5 to 8.0 × 10 - 3 mol/L. The detection limit was 1.0 × 10 - 6 mol/L based on S / N = 3.