Bifunctional Fe@PCN-222 nanozyme-based cascade reaction system: Application in ratiometric fluorescence and colorimetric dual-mode sensing of glucose

This work innovatively integrated the peroxidase-mimicking activity and red emission property of Fe@PCN-222 framework, designed a cascade reaction system for dual-mode glucose sensing. The Fe3+ doping significantly improved the catalytic activity of Fe@PCN-222 that can oxidize the substrate o-phenylenediamine (OPD) to generate diminophenazine (DAP) with emission at 566 nm in the presence of H2O2. Similarly, the Fe@PCN-222 was used to catalyze the colorless TMB to produce blue oxidized TMB (oxTMB) showed absorption at 652 nm. When coupled with glucose oxidase (GOx), the linear ranges of ratiometric fluorescence mode and colorimetric mode for glucose sensing were 1-100 and 10-300 mu M, respectively. And the limits of detection (LOD) of 0.78 and 2.41 mu M for two modes were obtained, respectively. In addition, the practicability of Fe@PCN-222 nanozymebased cascade reaction system for detection of glucose in human serum and saliva samples was successfully investigated. It is of great importance to integrate more functions into one skeleton to achieve dual-mode and optimal-performance sensing for expanding potential applications.