Stable and Biocompatible Monodispersion of C in Water by Peptides.

The lack of solubility in water and the formation of aggregates hamper many opportunities for technological exploitation of C. Here, different peptides were designed and synthesized with the aim of monomolecular dispersion of C in water. Phenylalanines were used as recognizing moieties, able to interact with C 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 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 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. AFM measurements showed that C is monodispersed. Electrospray ionization mass spectrometry determined a stoichiometry of C@(FGGGF). Molecular dynamics simulations showed that the peptides assemble around the C cage, like a candy in its paper wrapper, creating a supramolecular host able to accept C in the cavity. The peptide-wrapped C is fully biocompatible and the C "dark toxicity" is eliminated. C@(FGGGF) 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.