An enzyme-free self-cascade catalytic dual-read biosensor for noninvasive detection of glucose based on oxidase-mimic Fe-MOF

Metal-organic framework (MOF) materials have attracted much attention in the glucose detection owing to their high porosity and diverse catalytic sites. In this study, we synthesized Fe-MOF material with both glucose oxidase (GOD) activity and peroxidase (POD)-like activity. Mechanistically, Fe-MOF with GOD activity catalyze decomposition of glucose into H₂O₂ and gluconic acid, which self-cascade catalysis catalyze H₂O₂ decomposition to yield hydroxyl radical (•OH) by means of POD activity. •OH can oxidize the chromogenic substrate o-phenylenediamine (OPD) to yellow product 2,3-diaminophenazine (DAP), which causes strong absorption of the UV visible spectrum at 450 nm. Concurrently, a distinct fluorescence emission peak emerges at 565 nm and the intrinsic fluorescence of Fe-MOF at 465 nm exhibits fluorescence resonance energy transfer (FRET)-mediated quenching. Therefore, a dual-read biosensor for the quantification of glucose was proposed based on Fe-MOF with the aid of colorimetric and ratiometric fluorescence signals of I₅₆₅/I₄₆₅. The LOD was as low as 0.71 μM and 0.69 μM, respectively. Satisfactory recovery and low relative standard deviation were achieved in real human saliva samples.