Tiny but mighty! N,N-dimethyl-4-(5-nitrothiophen-2-yl)aniline, a push-pull fluorescent dye for lipid droplet imaging

Lipid droplets (LDs) are ubiquitous cellular organelles with a neutral lipid core containing triacylglycerols and cholesteryl esters surrounded by phospholipids. Recent findings indicate that LDs are intricately linked to diseases, such as cancer and neurological disorders, in addition to their roles in cellular senescence and immune responses. Herein, we describe a simple yet robust push-pull molecule, N,N-dimethyl-4-(5-nitrothiophen-2-yl) aniline (NiTA), as a versatile LD fluorescent probe. NiTA showed an absorption spectrum with a substantial bathochromic shift and a fluorescence spectrum with excellent solvatochromism. Leveraging the remarkable photophysical features of NiTA, we stained LDs in major immune cells, including T and B cells, and macrophages, and monitored the changes in LDs under oxidative and starvation conditions. Furthermore, we demonstrated the applicability of NiTA for visualizing the organization of medaka fish (Oryzias latipes) embryos during development. We expect the small yet powerful NiTA to be utilized in various applications, including fluorescence mapping to observe LD numbers, morphology, and polarity changes in animals and cells.