Cytosine-assisted synthesis of gold nanochains and gold nanoflowers for the construction of a microperoxidase-11 based amperometric biosensor for hydrogen peroxide

A simple method was developed for synthesis of network-like gold nanochains and gold nanoflowers in the presence of cytosine by reduction of tetrachloroauric acid with sodium borohydride and ascorbic acid, respectively. The resulting gold nanocrystals were coated with microperoxidase-11 via electrostatic interactions. Electrodes modified with protein-coated gold nanochains or nanoflowers display well-defined and quasireversible redox peaks and enhanced high electrocatalytic activity toward the reduction of H2O2 that is due to direct electron transfer to the protein. The effects were exploited for the amperometric detection of H2O2 with a linear response from 0.5 μM to 0.13 mM (for the gold nanochains) and from1.0 μM to 0.11 mM (for the gold nanoflowers), respectively. The sensor shows lower detection limit and faster response time than sensors based on the use of spherical gold nanoparticles.