Polarity-Sensitive and Membrane-Specific Probe Quantitatively Monitoring Ferroptosis through Fluorescence Lifetime Imaging.

As a new form of regulated cell death, ferroptosis is closely related to various diseases. To interpret this biological behavior and monitor related pathological processes, it is necessary to develop appropriate detection strategies and tools. Considering that ferroptosis is featured with remarkable lipid peroxidation of various cell membranes, it is logical to detect membranes' structural and environmental changes for the direct assessment of ferroptosis. For this sake, we designed novel polarity-sensitive fluorescent probes Mem-C 1 C 18 and Mem-C 18 C 18 , which have superior plasma membrane anchorage, high brightness, and sensitive responses to environmental polarity by changing their fluorescence lifetimes. Mem-C 1 C 18 with much less tendency to aggregate than Mem-C 18 C 18 outperformed the latter in high resolution fluorescence labeling of artificial vesicle membranes and plasma membranes of live cells. Thus, Mem-C 1 C 18 was selected to monitor plasma membranes damaged along ferroptosis process for the first time, in combination with the technique of fluorescence lifetime imaging (FLIM). After treating HeLa cells with Erastin, a typical ferroptosis inducer, the mean fluorescence lifetime of Mem-C 1 C 18 displayed a considerable increase from 3.00 to 4.93 ns, with a 64% increase (corresponding to the polarity parameter Δ f increased from 0.213 to 0.232). Therefore, our idea to utilize a probe to quantitate the changes in polarity of plasma membranes proves to be an effective method in the evaluation of the ferroptosis process.