A novel three-stage continuous sensing platform for H2O2 and cholesterol based on CuFeS2 nanozyme: Theoretical calculation and experimental verification

It is still a challenge to establish a facile and reliable sensing platform with broad linear range. In this work, an innovative substrate concentration-regulated strategy was developed for design of three-stage continuous colorimetric sensing platform for H2O2, vastly broadening the detecting linear range of the sensor. In detail, a novel nanozymes, the hollow CuFeS2 nanospheres with excellent peroxidase-like activity was synthesized, which could catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) by H2O2. Cytotoxicity test toward HUVEC and Hela cells verified the good biocompatibility of CuFeS2, guaranteeing its safety in biological applications. DFT theoretical calculation and experimental results both proved that the H2O2 adsorption capacity of CuFeS2 was higher than that of CuS and FeS. On this basis, a three-stage continuous sensing platform with broad detecting range by adjusting the concentration of TMB was developed. The proposed method was also successfully applied in detecting H2O2 in milk samples. Besides, coupled with cholesterol oxidase (ChOx), a cascade catalyzed colorimetric sensing platform for determining cholesterol had been constructed. Thus, this work not only provides the excellent performance of nanozymes, but also opens up a new avenue for designing sensing platform with extra-wide detecting range.