Arylidene-Imidazolones with Three Electron-Donating Substituents as Fluorogenic Dyes for Lipid Droplets of Living Cells

Objective: A pair of fluorogenic dyes with three electron-donating groups, based on arylideneimidazolones, is presented. Methods: The formation of imines of the corresponding aldehydes with the subsequent [3 + 2] cycloaddition was used for the synthesis of arylidene-imidazolones. The optical properties of the new compounds were studied. The fluorescence microscopy was used for imaging lipid droplets of the living cells, labeled by the dyes. Results and Discussion: We discovered that a pair of the proposed substances is characterized by a significant bathochromic shift of the absorption and emission maxima, as well as by a noticeable variation of the position of the emission maximum depending on the properties of the environment. We demonstrated that (Z)-5-(3,5-bis(dimethylamino)-4-(ethylamino)benzylidene)-2,3-dimethyl-3,5-dihydro-4H-imidazol-4-one can stain lipid droplets in HeLa Kyoto and Huh 7.5 cell lines. Conclusions: We designed a new selective fluorogenic dye based on arylidene-imidazolones and showed that it can be applicable for lipid droplets labeling in living cells.