Stable and Biocompatible Monodispersion of C 60 in Water by Peptides

The lack of solubility in water and the formation of aggregates hamper many opportunities for technological exploitation of C 60 . Here, different peptides were designed and synthesized with the aim of monomolecular dispersion of C 60 in water. Phenylalanines were used as recognizing moieties, able to interact with C 60 through π-π stacking, while a varying number of glycines were used as spacers, to connect the two terminal phenylalanines. The best performance in the dispersion of C 60 was obtained with the FGGGF peptidic nanotweezer at a pH of 12. A full characterization of this adduct was carried out. The peptides disperse C 60 in water with high efficiency, and the solutions are stable for months both in pure water and in physiological environments. NMR measurements demonstrated the ability of the peptides to interact with C 60 . AFM measurements showed that C 60 is monodispersed. Electrospray ionization mass spectrometry determined a stoichiometry of C 60 @(FGGGF) 4 . Molecular dynamics simulations showed that the peptides assemble around the C 60 cage, like a candy in its paper wrapper, creating a supramolecular host able to accept C 60 in the cavity. The peptide-wrapped C 60 is fully biocompatible and the C 60 "dark toxicity" is eliminated. C 60 @(FGGGF) 4 shows visible light-induced reactive oxygen species (ROS) generation at physiological saline concentrations and reduction of the HeLa cell viability in response to visible light irradiation.