Stable and Biocompatible Monodispersion of C₆₀ in Water by Peptides

Abstract

The lack of solubility in water and the formation of aggregates hamper many opportunities for technological exploitation of C60. Here, different peptides were designed and synthesized with the aim of monomolecular dispersion of C60 in water. Phenylalanines were used as recognizing moieties, able to interact with C60 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 C60 was obtained with the FGGGF peptidic nanotweezer at a pH of 12. A full characterization of this adduct was carried out. The peptides disperse C60 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 C60. AFM measurements showed that C60 is monodispersed. Electrospray ionization mass spectrometry determined a stoichiometry of C60@(FGGGF)4. Molecular dynamics simulations showed that the peptides assemble around the C60 cage, like a candy in its paper wrapper, creating a supramolecular host able to accept C60 in the cavity. The peptide-wrapped C60 is fully biocompatible and the C60 “dark toxicity” is eliminated. C60@(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.

Dissecting the Supramolecular Dispersion of Fullerenes by Proteins/Peptides: Amino Acid Ranking and Driving Forces for Binding to C60

“…If we consider the extended π-system of the fullerene, it is not surprising that aromatic amino acids such as tryptophan, tyrosine, phenylalanine, and histidine interacted the most with it ( Figure 3 ) [ 20 , 24 , 33 , 34 , 35 , 39 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 ]. In particular, Trp exhibited the largest value of binding energy among the twenty proteinogenic amino acids.…”

“…Supramolecular approaches can preserve these properties [ 19 ]. Recently, it was demonstrated that it is possible to use peptides [ 20 ] and proteins [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ] as supramolecular hosts for the non-covalent dispersion of fullerenes [ 21 ]. Different proteins, such as albumins [ 22 , 23 ], lysozyme [ 23 , 24 , 25 , 26 ], pepsin [ 27 ], trypsin [ 27 ], or natural protein surfactants [ 28 ] were used for the mono-molecular dispersion of pristine fullerenes in a physiological environment.…”

“…Detailed knowledge about the formation of complexes of peptides/proteins with C 60 can advance bio-based applications of fullerenes [ 35 ]. For instance, inhibitors can be developed by increasing the peptide/fullerene binding [ 32 , 36 , 37 , 38 ], the antioxidant properties of fullerenes can be enhanced by protein interaction [ 39 ], and fullerenes’ ability to generate ROS under irradiation can be tuned [ 20 , 23 , 25 , 26 , 40 ].…”

A Bio‐Conjugated Fullerene as a Subcellular‐Targeted and Multifaceted Phototheranostic Agent

“…[ 45–47 ] Proteins and peptides can be used as biocompatible hosts for fullerenes, allowing the dispersion of fullerenes as single molecules in physiological environments to prevent aggregation phenomena. [ 48–53 ] In particular, lysozyme binds and disperses C 60 in water, and the resulting C 60 @lysozyme complex is still photoactive, generating significant quantities of ROS upon visible light irradiation, while remaining biocompatible in dark conditions. [ 48 ] It was shown that irradiation of C 60 @lysozyme with visible light significantly reduced the viability of HeLa cells in vitro, making it a candidate for PDT.…”

Spiky Gold Nanoparticles for the Photothermal Eradication of Colon Cancer Cells

“…The interaction with proteins may affect the photophysical properties of photosensitizers, [ 56 , 57 , 58 , 59 , 60 , 61 ] so we evaluated the BGNP performances in a physiological-like conditions, investigating the possible effects of the biomolecular corona during laser the irradiation/heating process [ 44 ]. We repeated the irradiation experiment for the FBS-dispersed BGNPs, using the highest concentration of BGNPs (0.25 mM Au 0 BGNPs).…”