Studies on solvent induced fluorescence properties of styryl dye, LDS 798, to develop in vitro and in situ assay techniques

The styryl group of dyes has been used in cellular studies for over 50 years because of their solvatochromic and/ or electrochromic properties. Here we report characterization of solubility and solvatochromic properties of a near infra-red amiophenylstyrylquinolinum dye, styryl 11 or LDS 798. We have extended our studies to small unilamellar vesicles, lipid based nanoparticles and live cells. Our cellular studies show that LDS 798 preferentially localizes in mitochondria and its fluorescence lifetime changes with change in mitochondrial membrane potential. We have used this change in lifetime as an early marker for mitochondria-dependent apoptosis. We also found that solvatochromic properties of this dye, used in tandem with fluorescence correlation spectroscopy, can be used to efficiently determine the diffusion coefficient and hence the size of the submicron lipid based particles. This dye has the potential to provide essential information about liposomal structures and mitochondrial potential changes in vitro and in situ respectively.