Protein-mediated sponge-like copper sulfide as an ingenious and efficient peroxidase mimic for colorimetric glucose sensing.

Strenuous efforts have been made to develop nanozymes for achieving the performance of natural enzymes to broaden their application in practice, but the fabrication of high-performance and biocompatible nanozymes facile and versatile approaches has always been a great challenge. Here, sponge-like casein-CuS hybrid has been facilely synthesized in the presence of amphiphilic protein-casein through a simple one-step approach. Casein-CuS hybrid exhibits substrates-dependent peroxidase-like activity. Casein-CuS hybrid exhibits well peroxidase-like activity with 3,3',5,5'-tetramethylbenzidine (TMB) and 1,2-diaminobenzene (OPD) as substrates, and the affinity of OPD towards the hybrid nanozyme is much higher than that of TMB. More importantly, due to the high affinity of OPD and the well biocompatibility of the hybrid nanozyme, a superior enzyme cascade for glucose based on the well cooperative effect of casein-CuS hybrid and glucose oxidase is developed. The proposed glucose sensor exhibits a wide linear range of 0.083 to 75 μM and a detection limit of 5 nM. This suggests the promising utilization of protein-metal hybrid nanozymes as robust and potent peroxidase mimics in the medical, food and environmental detection fields.