Mn Single-Atom Nanozymes with Superior Loading Capability and Superb Superoxide Dismutase-like Activity for Bioassay

Single-atom nanozymes (SANs) with highly exposed active sites and remarkable catalytic activity have shown noteworthy practicability in heterogeneous catalysis-based bioassay. Nevertheless, most of them were reported with peroxidase-like activity and ordinary loading capability. It is still a challenge to prepare high-loading SANs with desirable superoxide dismutase (SOD)-like activity. In this work, Mn SAN was successfully confined in the frameworks of Prussian blue analogues formed on Ti3C2 MXene sheets with the assistance of massive surfactants, which show a superior loading efficiency of 13.5 wt % (typically <2.0 wt %). The prepared Mn SAN exhibits desirable superoxide radical anion elimination capability because of its SOD-like activity. Moreover, due to the wide-spectrum absorption behavior of the carriers, Mn SAN shows a synergistically quenching efficiency up to 98.89% on the emission of the reactive oxygen species-mediated chemiluminescent (CL) system. Inspired by these features, a CL quenching method was developed on a lateral flow test strip platform by utilizing Mn SAN as a signal quencher and acetamiprid as a model analyte. The method for detecting acetamiprid shows a detection range of 1.0-10,000 pg mL-1 and a limit of detection of 0.3 pg mL-1. Its accuracy has been validated by detecting acetamiprid in medicinal herbs with acceptable recoveries. This work opens an avenue for preparing SANs with a surfactant-assisted protocol and pioneers the study of SANs with SOD-like activity in bioassay.