A family of push-pull bio-probes for tracking lipid droplets in living cells with the detection of heterogeneity and polarity.

Lipid droplets (LDs) are multi-functional organelles with the storage of lipid and participating in a variety of physiological processes, including membrane transport and signal transduction. The dysfunction of LDs has been reported to be associated with multiple diseases such as obesity, diabetes, atherosclerosis, and cancer in research. Herein, we designed and synthesized a family of push-pull bio-probes (LDP1-LDP4) based on thiophene or 3,4-ethylenedioxythiophene, which is also called EDOT. LDP1-LDP4 showed positive solvatochromic effect from toluene to ethanol and the maximum fluorescence wavelength redshifted to 165 nm. It was found that the four probes showed significant increase in fluorescence intensity from PBS to oil. LDP1-LDP4 displayed excellent biocompatibility and good optical properties and had substantially facilitated to track LDs with detecting heterogeneity. LDP4 was also used to expose the difference in the polarity of LDs and cytoplasm.