Visualization of intracellular lipid droplets using lipophilic benzothiazole-based push-pull fluorophores at ultralow concentration

In this study we describe the development of new lipophilic and biocompatible benzothiazole-based push-pull fluorophores as potent fluorogenic probes for the specific staining of intracellular lipid droplets (LDs) at ultralow concentration (≤100 nM). These new fluorophores, harboring a D-π-A framework featuring an extended π-conjugated spacer, a lipophilic tertiary amine (D) and hydrophobic aryl groups (A), were prepared by an efficient and practical synthetic route. The photophysical studies of these compounds underlined their high polarity sensitivity, characterized by a strong solvatochromic effect and the large Stokes shifts values (λem 465–630 nm, Δλ up to 6751 cm−1). Finally, the in cellulo investigations of D1 revealed its ability to selectivity accumulate in LDs and to allow their remarkable visualization using confocal fluorescence microscopy.