A pyridinemalononitrile-based polarity-responsive fluorescent probe for lipid droplet dynamics tracking and nonalcoholic fatty liver disease diagnosis.

Lipid droplets (LDs) are highly dynamic organelles that play crucial roles in various physiology processes, and their excessive accumulation is closely associated with nonalcoholic fatty liver disease (NAFLD). Therefore, the rational design of fluorescent probes for LDs detection is of significant importance. Inspired by dicyanomethylene-4H-pyran-based dyes, we designed and synthesized three pyridine malonitrile-based fluorescence probes (PMs). Among them, PM-3 exhibited a pronounced polarity-dependent fluorescence behavior, displaying strong fluorescence exclusively in low-polarity solvents such as toluene and dioxane. Moreover, PM-3 demonstrated excellent chemical stability and photostability, with an excitation wavelength compatible with the commonly used 488 nm laser. This probe can precisely label LDs and enable real-time monitoring of their dynamic Behavior in living cells. More importantly, PM-3 showed promising performance in distinguishing fatty liver tissue from normal tissue through fluorescence imaging. Taken together, PM-3 serves as a highly effective fluorescent tool for investigating the functional roles in LDs.