Synthesis and characterization of a fullerenol derivative for the development of cell penetration vehicles

Several biological barriers are generally responsible for the limited delivery of cargoes at the cellular level. These barriers include overpassing the plasma membrane, escaping from the endosomes after cellular uptake, and eventually, crossing the nuclear envelope. Fullerenols have unique structural features and possess suitable properties for interaction with the cells. This study aimed to synthesize and characterize a fullerenol derivative with desirable characteristics (size, surface charge, surface functionality, hydrophilicity) to develop cell penetration vehicles. Fullerenol was synthesized from fullerene C₆₀ solubilized in toluene followed by hydroxylation with aqueous hydrogen peroxide in the presence of tetra-n-butylammonium hydroxide (TBAH) as a phase transfer catalyst. The obtained product was purified by a Florisil chromatography column (water as the eluent) followed by dialysis (cellulose membrane dialysis tubing) and freeze-drying (yield 66 %). Subsequently, a silane coupling agent was conjugated on the fullerenol surface to render free amine functional groups for further covalent functionalization with other molecules. Characterization via Scanning Electron Microscopy (SEM), Dynamic light scattering (DLS), FTIR-ATR, Raman, and UV–visible spectroscopies was conducted to evaluate composition, size, morphology, surface functionality, and structural properties. We are currently working on the conjugation of the potent cell-penetrating agents Buforin II (BUFII) and the Outer membrane protein A (OmpA) on the surface of the fullerenol to estimate whether cell penetration and endosome escape are improved with respect to conventional polymeric vehicles and our own previous developments with Iron Oxide Nanoparticles.