Multicolor colorimetric visual detection of Staphylococcus aureus based on Fe3O4–Ag–MnO2 composites nano-oxidative mimetic enzyme

Novel Fe3O4–Ag–MnO2 composites were successfully synthesized. It was noteworthy that the obtained Fe3O4–Ag–MnO2 composites were found to possess three types of enzyme-mimicking activities, including peroxidase-like, catalase-like and oxidase-like activities. Taking advantage of the oxidase properties of Fe3O4–Ag–MnO2, the direct oxidation of TMB could be catalyzed to generate blue oxidation products without H2O2. The oxidase-like activity of Fe3O4–Ag–MnO2 were carefully studied. Based on the Fe3O4–Ag–MnO2-TMB system, a fast, sensitive and intuitive multicolor colorimetric method for Staphylococcus aureus (S. aureus) detection was established under the optimized conditions. The proposed method allows the detection of S. aureus with a detection limit of 3.7 cfu mL−1 and a linear range of 10–106 cfu mL−1. This new colorimetric method has been successfully proved to be applicable to the detection S. aureus of food samples.