Simultaneous monitoring of polarity changes of lipid droplets and lysosomes with two-photon fluorescent probes.

Intracellular polarity is an essential feature of cell physiological state and abnormal polarity changes of various organelles are related to many diseases. Thus, monitoring of polarity changes of multiple subcellular in living cells contributes to understanding different physiological and pathological processes more accurately. However, most of the previous reports on polarity probes mainly monitored the polarity of a single organelle. Therefore, we designed and synthesized two unique polarity-sensitive fluorescent probes LDs-TPFP and Lyso-TPFP, which can be selectively located in lipid droplets (LDs) and lysosomes respectively, to obtain more subcellular information in living cells. Thanks to the strong intramolecular-charge-transfer (ICT) characteristics of probes, the fluorescence intensity and emission wavelength would change with the polarity of the surroundings of cells. Moreover, LDs-TPFP and Lyso-TPFP exhibits large Stokes shift and excellent biocompatibility. Through fluorescence imaging, the probes can effectively distinguish normal cells from cancer cells. In addition, the results of two-photon confocal fluorescence imaging indicated that LDs and lysosomes have discrepant polarity change behaviors under different physiological conditions.