Gold–platinum bimetallic nanoclusters with enhanced peroxidase-like activity and their integrated agarose hydrogel-based sensing platform for the colorimetric analysis of glucose levels in serum

This work presents a novel and facile strategy for the fabrication of gold-platinum bimetallic nanoclusters (Au-PtNCs) with adjustable Au/Pt molar ratios by a one-pot synthetic route. It was unexpectedly found that the prepared Au-PtNCs with an optimal Au/Pt molar ratio (1 : 1) could exhibit greatly enhanced peroxidase-like catalytic activity and chemical stability toward harsh conditions due to the synergistic effect of the two atoms, in contrast with pure AuNCs. These prominent advantages render Au-PtNCs capable of sensitive and selective colorimetric detection of glucose by means of a NCs-glucose oxidase (GOx) cascade-catalyzed system using 3,3',5,5'-tetramethylbenzidine (TMB) as a chromogenic substrate. This assay can be used not only for visual detection of glucose by the naked eye but for reliable and convenient quantification in the range from 5 to 55 μM with a detection limit of 2.4 μM. Importantly, to widen the application of point-of-care testing (POCT) of glucose to biomedical diagnosis, an integrated agarose hydrogel-based sensing platform comprising NCs, GOx and TMB was rationally designed. It was demonstrated that this sensing platform could serve as a reagentless and instrument-free platform for direct visualization of glucose with different levels in human serum, as the results were in good accordance with those obtained from a free NC-involved detection system as well as from a commercial blood glucometer.