Perylene bisimide-incorporated water-soluble polyurethanes for living cell fluorescence labeling

Abstract Perylene bisimides (PBIs) possess high fluorescence quantum yields, high extinction coefficients, and high chemical and photophysical stability. However, their poor water-solubility limits their potential biomedical applications. In this work, we show a facile one-step condensation method to synthesize PBI-incorporated polyurethanes (HDI-PBI-PEG) from hexamethylene diisocyanate (HDI), PBI, and poly(ethylene glycol) (PEG). Results show that copolymerization greatly improves the solubility of PBIs in polar–organic solvents and water. More importantly, HDI-PBI-PEG shows strong fluorescence in aqueous solutions and low cytotoxicity toward mammalian cells. Various living cells, including L929 cells, macrophages, and skov-3 cells, can internalize HDI-PBI-PEG; the labeled cells show intensive and stable light emission. Furthermore, folic acid-conjugated HDI-PBI-PEG exhibits significantly higher efficiency to label skov-3 cells than normal mammalian cells, thereby showing the possibility of achieving selective cell labeling. These results demonstrate the great potential of using HDI-PBI-PEG as a universal cell-labeling agent.