UV-Induced Degradation of Microcystin-LR Mediated by a Ratiometric Fluorescence Probe for the Visual Detection of Microcystin-LR

Microcystin-LR (MC-LR), a natural toxin produced by cyanobacteria, poses a significant threat to human health and ecological systems. Rapid and accurate quantification of MC-LR plays a critical role in the early warning systems and environmental risk assessment of eutrophic water bodies. Herein, we identified a unique UV-induced degradation mechanism of MC-LR mediated by a newly developed ratiometric fluorescence probe ASS12 . Under UV irradiation, the probe undergoes a specific reaction with MC-LR, during which its fluorescence color changes sequentially from yellow to red and ultimately to blue within 20 min. This dynamic response enables visual detection of MC-LR by the naked eye and significantly enhances the ratiometric fluorescence signal for MC-LR at the I 465 / I 555 ratio by 77-fold. For the first time, we found that the long alkyl chain and aldehyde group of the probe serve as key molecular recognition sites during MC-LR detection. Furthermore, the ratiometric fluorescence signal of the probe exhibits a strong correlation with the concentration of MC-LR across different regions of plateau lakes, effectively reflecting the spatial distribution patterns of MC-LR within these aquatic environments. Using a multivariate linear parametrization model linking the fluorescence ratio and water quality parameters, the distribution of MC-LR in lakes can be determined. This study provides a valuable theoretical foundation and technical approach for the development of novel MC-LR monitoring tools and the visual assessment of water eutrophication.