Synthesis of a Red-Emitting Polarity-Sensitive Fluorescent Probe Based on ICT and Visualization for Lipid Droplet Dynamic Processes

Abnormal lipid droplets (LDs) have been recognized as critical factors in many diseases because they are metabolically active and dynamic organelles. Visualization for LD dynamic processes is fundamental for elucidating the relationship of LDs and related diseases. Herein, a red-emitting polarity-sensitive fluorescent probe (TPA-CYP) based on intramolecular charge transfer (ICT) was proposed, which was constructed by employing triphenylamine (TPA) and 2-(5,5-dimethyl-2-cyclohex-1-ylidene)propanedinitrile (CYP) as electron donor and acceptor moiety, respectively. The spectra results underlined the excellent characteristics of TPA-CYP, such as high polarity sensitivity (Δ f = 0.209 to 0.312), strong solvatochromic effect (λ em 595–699 nm), and the large Stokes shifts (174 nm). Moreover, TPA-CYP exhibited a specific ability to target LDs and effectively differentiated cancer cells and normal cells. Surprisingly, TPA-CYP had been successfully applied to dynamic tracking of LDs, not only in inflammation induced by lipopolysaccharide (LPS), the process of oxidative stress, but also in live zebrafish. We believe that TPA-CYP could serve as a powerful tool to gain insight into the dynamics of LDs and to understand and diagnose LD-associated diseases.