Structural effects of amphiphilic protein/gold nanoparticle hybrid based nanozyme on peroxidase-like activity and silver-mediated inhibition†
Abstract
Understanding structure–property correlations of nanozymes is critical in the rational design and fabrication of nanozymes with effective activity and smart multifunction. Here, an amphiphilic protein, β-casein, was chosen as a flexible modifier to fabricate a β-casein–AuNP hybrid nanozyme. The physicochemical properties including protein surface density and particle sizes can be easily controlled by the molar ratio of [precursor]/[protein]. Then, the structure–property correlation of the nanozyme was systematically investigated. Both the surface density of the protein and the nanoparticle size influence the peroxidase-like activity and silver-mediated inhibition. β-Casein–AuNP with a moderate AuNP core size and protein surface density has the lowest apparent Km value of CM–AuNPs with TMB and H2O2, and hence the highest enzyme activity. Furthermore, the silver ion has been found to selectively inhibit the catalytic activity of β-casein–AuNPs due to the capping microenvironment provided by the protein. Since the bound silver ions can be effectively reduced to Ag0 by protein on the AuNP surface, the highest inhibition potency by silver is obtained for a β-casein–AuNP nanozyme with the lowest protein surface density and largest particle size. Importantly, a β-casein–AuNP (4.3 nm) based silver sensor is highly sensitive for sensing silver ions with a wide linear range of 0.1–10 μM, and has a low detection limit of 10 nM. The fundamental understanding of the structure–property relationship of nanozymes could provide guidance in the further development of easily prepared, effective, and low-cost nanozymes and their utilization in numerous areas.