Quercetin@ZIF-90 as a novel antioxidant for label-free colorimetric ATP sensing at neutral pH

Quercetin is a nature polyphenolic flavonoid compound, which act as antioxidant and radical scavengers in cells. However, such activities strongly depend on the intracellular microenvironment, which has become an urgency to develop a more stable method for better use of quercetin. Herein, we report a facile approach to fabricate Quercetin@ZIF-90 (QZ) with a narrow size distribution about 100 nm, the synthesized QZ exhibits considerable antioxidant and radical scavenger ability comparing to bare quercetin. Moreover, the experiment results indicated that QZ was sensitive to adenosine 5′-triphosphate (ATP) and pH, thus QZ was applied as a novel antioxidant for the determination of ATP. In brief, though 3, 3′, 5, 5′-tetramethylbenzidine (TMB) could be oxidized to blue cation radical complex by oxidase-like BSA-MnO 2 nanosheets (MNs) at neutral pH, QZ could sufficiently protect against MNs-induced TMB cation radicals reaction, which means no obvious color change in MNs-TMB system after the addition of QZ. However, ATP could induced collapse of QZ due to the interaction between ATP and Zn 2+ allowing the release of quercetin from ZIF-90 shell, and the inhibition effect to the MNs was weakened, leading to the recovery of blue oxTMB. In this way, a novel “Off-On” colorimetric method for ATP sensing was established, and the method displayed a good linear relationship ranging from 2.0 μ mol L −1 to 80.0 μ mol L −1 . The reported strategy is also capable of ATP sensing in MCF-7 cell lysates, which illustrated our method exhibited high sensitivity and selectivity.