AIE Fluorescent Nanozyme-Enabled Ratiometric Sensing Platform for Selective Detection of Ascorbic Acid and Alkaline Phosphatase

Ascorbic acid (AA) and alkaline phosphatase (ALP) are essential biomolecules involved in numerous physiological and pathological processes. However, conventional nanozyme assays based on AA reduction or ALP-mediated AA generation often suffer from interference from coexisting reductants, compromising their selectivity and analytical reliability. Here, we reported a rationally designed fluorescent nanozyme, ZIF-8/Ru@TPE, constructed by anchoring ultrasmall Ru nanoparticles onto ZIF-8 and assembling them with the aggregation-induced emission (AIE) luminogen tetraphenylethylene (TPE). The resulting hybrid exhibited strong intrinsic fluorescence at 445 nm and remarkable peroxidase-like activity. Upon the addition of H₂O₂ and <i>o</i>-phenylenediamine (OPD), ZIF-8/Ru@TPE catalyzed OPD oxidation to form the fluorescent product 2,3-diaminophenazine (DAP), yielding a distinct emission peak at 570 nm while quenching the TPE fluorescence at 445 nm. Notably, AA triggered a self-amplified ratiometric response by simultaneously inhibiting OPD oxidation and generating an additional fluorophore through the reaction of dehydroascorbic acid with OPD, achieving high selectivity over other reductants. Exploiting ALP-catalyzed AA production, this platform was successfully extended to ALP activity determination in serum. This study presents a versatile nanozyme-based ratiometric sensing strategy for selective detection of AA and ALP, offering great potential for accurate bioanalysis in complex samples.