Ratiometric fluorometric and colorimetric dual-mode sensing of glucose based on gold-platinum bimetallic nanoclusters

The synthesis of highly sensitive and selective luminescent probes provides a vital and efficient approach for diagnosing and preventing clinical diseases. In this work, gold-platinum bimetallic nanoclusters (Au - PtNCsGMP) were synthesized with guanosine monophosphate (GMP) as the capping agent, which possessed strong fluorescent emission at 418 nm, and also exhibited great peroxidase-like mimetic activity. Glucose can be catalyzed to generate H2O2 by glucose oxidase, in the presence of H2O2, o-phenylenediamine (OPD) regarded as a representative non-fluorescent substance was catalyzed by Au-PtNCs-GMP and produced fluorescent 2,3-diaminophenazine (DAP) with an emission wavelength of 560 nm. Furthermore, the colorless OPD was oxidized to yellow DAP with UV-vis absorption peak at 420 nm. The generation of DAP can efficiently quench the fluorescence signal of Au-PtNCs-GMP at 418 nm on account of inner filter effect (IFE). The decrease of Au-PtNCsGMP fluorescence and the increase of DAP fluorescence made it possible to detect glucose via ratiometric fluorometric intensity. Thus, a ratiometric fluorescent and colorimetric dual-mode sensing was achieved for glucose detection. The linear ranges of ratiometric fluorescence method and colorimetric method toward glucose were in the range of 0.01-0.4 mM and 0.05-0.4 mM, with the low limits of detection (LOD) of 7 mu M and 11 mu M, respectively. In addition, this dual-mode sensing method can be used for detecting glucose concentration in real biological samples with satisfying results, which provided a valuable and reliable strategy for glucose-related detections.