Triphenylamine-derived fluorescent probe: Synthesis and lipid droplet polarity imaging analysis

Lipid droplets are important parts of cells. They store lipids. They also help control cell balance. Notably, there exists a strong correlation between lipid droplet polarity and the progression of NAFLD. Accordingly, tracking variations in lipid droplet polarity permits the staged assessment of NAFLD. In this study, we picked triphenylamine as the electron donor. We used thiophene as the π-bridge. We also chose benzofuran as the electron acceptor. On this basis, a novel fluorescent probe (MDN) with a typical D-π-A architecture was rationally designed and synthesized for polarity detection. Specifically, the MDN probe showed special fluorescence when the environment was less polar. It had high sensitivity and good selectivity. Meanwhile, MDN had a big Stokes shift of 70 nm and its maximum fluorescence emission wavelength was over 600 nm in the test, which possess excellent optical properties Confocal imaging showed that the MDN probe matched well with intracellular structures. Also, the ClogP value of MDN was 10.876, indicating its favorable capability for lipid droplet targeting. Another study demonstrated that MDN can be used to monitor the changes of intracellular polarity. The experimental results verified that lipid droplet accumulation in liver tissues was significantly higher than that in other organs, accompanied by intense fluorescence signals. In summary, the polarity-responsive probe developed in this work possesses excellent targeting capability toward lipid droplets.