Photophysical characterization and the self-assembly properties of mono- and bis-pyrene derivatives for cell imaging applications

A series of fluorescent mono-(1-4) and bis-pyrene derivatives (5-7) were synthesized and their photo-physical and self-aggregation properties in solution were fully investigated by UV-vis and fluorescence spectroscopies and dynamic light scattering (DLS). While in dilute DMSO mono-pyrene derivatives 1-4 show the characteristic features of monomer emission, bis-pyrene derivatives 5-7 display both monomer and excimer emissions, the latter attributable to a dynamic process. The gelation behaviour of these compounds was also studied, and only mono-pyrene leucine derivative 1 was found to display efficient gelation in aromatic solvents, such as toluene and p-xylene, and in a polar solvent mixture, water/DMSO (4 : 1 v/v). Finally, mono-pyrenes 1-4 showed no apparent cytotoxic impact on A549 and RD cell lines; derivatives 1-5 showed accumulation within both live and fixed cells, and macropinocytosis was found to be the main pathway for 5 to enter into the cells.