A 3,4-dimethoxy-1,8-naphthalimide for lipid droplet imaging in live and fixed cells

Lipid droplets (LDs) are found in most eukaryotic cells and in addition to serving as lipid reservoirs, these highly dynamic organelles play fundamental roles in cell metabolism and growth. The study of LDs and their interactions with other cellular compartments provides new insights into normal cell biology and disease processes such as virus packaging, metabolic disorders, and cancer progression. Here we report the synthesis and comprehensive evaluation of two readily prepared, low molecular weight 3,4-dimethoxy-1,8-naphthalimides, as selective LD stains. The newly synthesised 1,8-naphthalimide derivative (DMN-LD), demonstrated impressive versatility compared to currently available options, by staining LDs in both live and fixed cells, as well as a three-dimensional spheroid, using both single and two-photon excitation. This new imaging agent has the potential to further unravel the complex biology of LDs, which are essential to cell survival, and when altered, underpin many disease states. [Display omitted] •DMN-LD is a solvatochromic fluorescent imaging agent for detection of lipid droplets at low concentrations.•Low molecular weight, readily accessible, non-toxic and bench stable.•Thoroughly characterised using co-localisation, feeding and starving experiments.•Suitable for live and fixed cell imaging applications.•Amenable to two-photon microscopy experiments and imaging in three-dimensional spheroid systems.•Images fundamental lipid droplet behaviours such as homotypic fusion events and interaction with other organelles