Rapid colorimetric detection of H2O2 in living cells and its upstream series of molecules based on oxidase-like activity of CoMnO3 nanofibers

Most studies on nanozymes in recent years have focused on enhancing their catalytic activity and synthesizing directly, although this task is still complicated. Bimetallic oxides are particularly desirable due to their mixed valence and structural properties. In this study, bimetallic oxide nanofibers (CoMnO3 NFs) were prepared using a quick and effective hydrothermal synthesis technique, and exhibited outstanding oxidase-like activity. The catalytic activity of CoMnO3 NFs displayed an inhibitory response on exposure to H2O2, which was applied in detecting H2O2 and its upstream molecules (glucose and uric acid). Based on this, a straightforward, affordable, and accurate colorimetric approach was developed by combining with 3,3′,5,5′-tetramethylbenzidine. Employing the oxidase activity rather than the traditional peroxidase activity to detect H2O2 drastically reduces the detection time. This method was also successfully used for in situ quantitative monitoring of intracellular H2O2, as well as detecting uric acid and glucose levels in human serum. Moreover, a smartphone-assisted colorimetric sensing system built on self-developed software was developed, enabling the on-site detection of H2O2 without laboratory instruments. This study established theoretical support for the valid design of bimetallic oxide nanozyme activity and might guide the development of detection systems for accurately analyzing biomarkers in foods and biochemical products.