In situ decorating of montmorillonite with ZnMn2O4 nanoparticles with enhanced oxidase-like activity and its application in constructing GSH colorimetric platform

Leaning from nature and taking advantage of nature is a one of important way in scientific research. In this work, as natural clay mineral, montmorillonite (Mt) was used to synthesize ZnMn2O4-Mt nanocomposites, in which ZnMn2O4 nanoparticles uniformly anchored on surface of Mt. Mt. with satisfied lamellar structure and biocompatibility can suppress the agglomeration of ZnMn2O4 nanoparticles, and thus increase its catalytic performance. ZnMn2O4-Mt is demonstrated to possess intrinsic oxidase-like activity, and is able to catalyze the oxidation of colorless 3,3,5,5-tetramethylbenzidine (TMB) into a blue substrate (ox-TMB) in the presence of dissolved oxygen. Kinetic study reveals ZnMn2O4-Mt possesses high affinity toward TMB. Coupled with reducibility of glutathione (GSH), a colorimentric sensing platform for GSH is developed. Interestingly, the linear detection range contains two segments of straight line with different slopes, and the detection limit is 0.52 μM. Catalytic mechanism experiments demonstrates that reactive oxygen species (ROS) produced in catalytic process are singlet oxygen (1O2) and superoxide anion radical (O2−). This method is also successfully applied in detection of GSH in serum samples. Thus, this work not only provides an effective strategy for designing nanozymes, but also proposes a potential detection method for GSH.