Constructing D-π-A-π dye to obtain red-emission fluorescent probe for structured illumination microscopy imaging of lipid droplet dynamics

Lipid droplets (LDs) are dynamic organelles interacting with a variety of intracellular organelles. Tracking intracellular LD dynamics employing synthetic small molecules is crucial for biological studies. Fluorescence imaging in the red and near infrared (NIR) region is more suitable for biological imaging due to its low phototoxicity and high signal-to-noise ratio. However, available LD-dyes in the red region with remarkable environmental sensitivity, selectivity for LDs staining are limited. Here, we constructed a red-emission D-π-A-π type LD-dye LD 688P with higher environmental sensitivity and suitable “calculated log P ” (Clog P ) for LDs dynamic imaging. LD 688P was proved to be highly selective and photostable for tracing LD fusion including multiple consecutive fusions and fusions in a centrosymmetric manner by super-resolution microscopy. We believe that the D-π-A-π skeleton would be an efficient strategy to construct red and even NIR-emission dyes. • A red-emission fluorescent probe for lipid droplets was developed. • A strategy of D-π-A-π to modify the dye conjugation to get red-shifted emission. • Lipid droplets dynamics in living cells were monitored with super-resolution imaging. • Multiple consecutive fusions and fusions in a centrosymmetric manner of LDs were observed.