A Novel method for the preparation of fluorescent C₆₀ poly(amino acid) composites and their biological imaging

Recently, fullerene (C₆₀) and its derivatives have been widely explored for many applications owing to their enriched physical and chemical properties. Specifically, the synthesis and biomedical applications of fluorescent C₆₀ have been extensively investigated previously. However, the preparation of polymer-functionalized fluorescent C₆₀ has not been reported thus far. In this study, water-dispersible fluorescent C₆₀ polymer composites were successfully synthesized through the combination of the thiol-ene click reaction and subsequent ring-opening polymerization. First, 2-aminoethanethiol was introduced on the surface of C₆₀ by the thiol-ene click reaction. The surface of amino group-functionalized C₆₀ (C₆₀-NH₂) was further modified with poly(amino acid)s via ring-open polymerization of GluEG N-carboxyanhydrides (NCAs). The morphology, functional groups, optical properties and biocompatibility were examined by a number of characterization equipment and assays in detail. We demonstrated that the resultant fluorescent C₆₀ poly(amino acid) (C₆₀-GluEG) composites have a small size (about 5 nm), high water dispersibility, intense fluorescence and high photostability. Cell viability results implied that the C₆₀-GluEG composites possess low cytotoxicity. Moreover, these C₆₀-GluEG composites can easily penetrate into live cells, indicating their great potential for biological imaging applications.