Bimetallic Au-Ag Nanoclusters as a Photo-Responsive Oxidase-Like Nanozyme for Antioxidant Detection and Intracellular...

Bimetallic nanoclusters (NCs) hold promise as catalytic materials, yet their potential as enzyme mimics remains largely unexplored. Here, we report the first demonstration that gold-silver nanoclusters (AuAgNCs) function as photo-responsive oxidase-like nanozymes. Under visible-light irradiation, AuAgNCs catalyze thiamine oxidation via a Type I photosensitization pathway, predominantly generating physiologically relevant peroxyl radicals (ROO•). The AuAgNCs outperform monometallic analogs, achieving enhanced catalytic efficiency with lower K_m and higher v _max than previously reported nanozymes. Utilizing these capabilities, we established a rapid (<6 min), reagent-free platform that enables: (i) selective detection of diverse physiological antioxidants, (ii) quantitative assessment of total antioxidant capacity (TAC) in simulated biofluids and consumer products, and (iii) dynamic tracking of intracellular redox alterations in normal and steatotic hepatocyte models. This versatile platform addresses critical limitations of conventional assays by employing in situ-generated biologically relevant radicals and high specificity for antioxidant detection, while offering mechanistic insight, operational simplicity, and broad applicability. Our findings expand the functional landscape of bimetallic nanoclusters, establishing them as powerful redox-active nanozymes for biomedical diagnostics, antioxidant evaluation, and redox biology.