A Novel Flavonol-based Fluorescent Probe for Detecting GSH Exhaustion in Polystyrene Microplastic-Induced Liver Injury.

Polystyrene microplastics (PS-MPs, <5 mm) are ubiquitous contaminants that accumulate in the liver through dietary exposure, leading to hepatocellular damage. However, the dynamic changes in glutathione (GSH) under PS-MPs exposure and its underlying mechanisms in liver injury remain poorly understood. In this study, we harnessed the tunable excited-state intramolecular proton transfer (ESIPT) properties of natural flavonols to develop a GSH-activated flavonol probe, BQ-N. Structurally, BQ-N incorporates a 2,4-dinitrobenzenesulfonyl (DNBS) moiety as a fluorescence-quenching group, enabling selective fluorescence restoration through a thiol-mediated nucleophilic substitution reaction. The BQ-N probe was successfully employed for real-time monitoring of GSH in living cells and in a mouse model of liver injury induced by PS-MPs exposure. Further mechanistic studies revealed that PS-MPs exposure downregulates the expression of Glutathione Peroxidase 4 (GPX4) and ferritin, while upregulating the expression of oxidative stress-related proteins heme oxygenase-1 (HO-1) and quinone oxidoreductase 1 (NQO1). These findings suggest that PS-MPs may mediate liver injury by activating the ferroptosis pathway through interference with GSH metabolism and redox balance. In summary, the BQ-N probe enables real-time visual monitoring of GSH via fluorescence imaging at both the cellular level and in isolated animal organs and provides an effective early detection tool for PS-MP-induced liver injury. Furthermore, it reveals partial molecular mechanisms of microplastic hepatotoxicity from the perspective of the GSH-ferroptosis axis, offering new insights for integrating environmental pollutant health risk assessment with molecular imaging technology.