Construction of a robust polarity sensitive platform and its application for tracking of lipid droplets decrease under oxidative stress in live cells

There are many hydrophilic and hydrophobic organelles and regions in cells, which play important roles in the physiological activities of cells. In this work, we have developed a new polarity sensitive fluorescent platform (DN-NR) to detect cell polarity and lipid droplets (LDs) evolution. DN-NR is composed of the fluorophores dansyl chloride (DN) and a nile red (NR) derivative. DN-NR can detect polarity changes in both green and red detection channels. Moreover, by taking advantage of solvatochromism and the aggregation-caused fluorescence quenching (ACQ) effect of chromophores, DN-NR responds to polarity changes via emission changes in both hydrophobic and hydrophilic environments. DN-NR possesses a strong positive solvatochromism with solvent polarity change, and the response mechanism was further investigated by lifetime measurement and DFT calculation. As proved by co-staining experiments, DN-NR can effectively detect LDs in living HeLa cells, and the LDs evolution was dynamically visualized. Experimental results indicated that oxidative stress induced by H2O2 treatment leads to a sharp decrease of LDs. Therefore, DN-NR has broad prospective applications for biomedical research and diagnosis in LDs tracking and analysis.