Effective PEGylation method to improve biocompatibility of graphene derivatives

The research on the use of graphene (G) in the biological applications has increased exponentially with emerging concerns regarding its biosafety and potential cytotoxicity. The modification of the surface with biocompatible polymers is a promising approach where poly(ethylene glycol) (PEG) have been extensively used. However, increasing water solubility may not be enough to make G biocompatible since it has different cytotoxicity mechanisms like absorbing cell nutrition on its wide surface area and creating reactive oxygen species through its functional groups. A PEGylation method that uses surface area of graphene oxide (GO) by taking advantage of its solubility in aqueous medium and simultaneously producing reduced GO (rGO) to eliminate the cytotoxicity that comes from functional groups might be a solution to improve biocompatibility and solubility of rGO which is an optimum graphene derivative for biological applications. To have surface PEGylated rGO instead of having edge PEGylated GO; P(PEGMA-co-MMA-co-PMA) copolymers were synthesized and coated on GO via pi-pi interactions through multiple pyrene units in the copolymer. Healed conjugated surface of rGO was used as an advantage to increase the efficiency of PEGylation by in-situ reduction of GO to rGO in the presence of copolymer to obtain biocompatible, water dispersible, highly PEGylated rGO.