New Trick from Old Dog: Probing the Light-Responsive Oxidase Mimic Activity of Au Nanoclusterzymes for Dual-Channel Biosensing

Although gold nanoclusters have been widely studied as nanoclusterzymes, their practical applications are limited by the requirement of unstable H2O2 when leveraging their typical peroxidase-like activity. Herein, the bovine serum albumin-protected gold nanoclusters (BSA-AuNCs) are found to exhibit visible light-responsive oxidase-like (L-OXD-like) activity, which can oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) to its oxidation state (ox-TMB) without requiring H2O2. The experimental study and theoretical calculation manifest that the photoinduced reactive oxygen species like singlet oxygen (1O2) and superoxide anion (•O2–), as well as part of the photogenerated holes, are found to be contributory to the high L-OXD-like activity. Furthermore, Förster resonance energy transfer and inner filter effects jointly quench the fluorescence of BSA-AuNCs in the oxidized TMB system. This dual-signal response (colorimetric signal from ox-TMB formation and fluorescent signal from fluorescence quenching) forms the basis of a versatile dual-mode biosensing platform. To demonstrate its utility, a proof-of-concept assay for α-glucosidase activity and the inhibitor is established using this photoexcited BSA-AuNC system. This work indicates the promise of BSA-AuNC nanoclusters in applications beyond biosensing that require controllable ROS generation.