Bimetallic MOFs-derived four-in-one CeCuOx/C nanozyme and its application for colorimetric detection of cysteine based on oxidase mimics

To address the limitations of natural enzymes, more and more artificial enzymes have been developed. As the most appropriate candidate, metal organic frameworks (MOFs) and MOFs-based derivatives have generated extensive interest due to their remarkable properties and potential applications in enzymes mimicry. In this work, Ce/Cu mixed metal oxides-carbon composite (CeCuO_x/C) was synthesized through a simple oxidation method with bimetallic MOFs CeCu-BTC as precursors. It was found that the prepared CeCuO_x/C possess four different enzyme-like activities, including peroxidase, oxidase, laccase and phosphatase mimetic activities. The kinetics parameters and potential influence factors of enzyme-like activities were studied and CeCuO_x/C exhibited high catalytic activity, excellent stability, and reusability. Additionally, a cysteine detecting method was established via oxidase-like activity of CeCuO_x/C. The linear response to the cysteine was in the range of 50 to 900 μM, and the limit of detection was 3.24 μM. The spiking recoveries were in the range 93.5–100.2 % for cysteine in artificial human urine samples and the relative standard deviations were found within the ranges of 1.2–2.9 %. This work presents a new approach for the design of multi-enzyme mimics and develops the potential of CeCuO_x/C for biological sensing.