Functionalization of graphene oxide for RNA delivery

Abstract

Two-dimensional graphene had considered as a good material in various applications owing to its extraordinary and exceptional electronic, thermal, mechanical and chemical properties. In this study, the biological application of graphene oxide (GO) has been explored. As a rapidly developing field, nanotechnology has been used in RNA delivery.

Dispersion of graphene sheets in different media as well as chemical functionalization are the important factors which influence their end applications. Basically, chemical functionalization allows GO to be processed easily and prevents the agglomeration in cell culture media. In addition, the intrinsic properties of graphene are maintained by this method. Hence, the development of chemical functionalization of graphene has been reviewed in this report. In general, covalent and non-covalent modifications are the two main functionalization methods for graphene.

In this research, GO was covalently functionalized with various hydrophilic and biocompatible polymers, including 2kDa polyethylene glycol (PEG), 2kDa polyethylenimine (LMW-PEI), 25kDa polyethylenimine (HMW-PEI), 30kDa Poly-L-Lysine (PLL) and 70kDa polyarginine (PArg) for the loading and delivery of RNA. Two different modifying agents, N-(3-Dimethylaminopropyl)-N’-ethylcarbodiimide (EDC) and potassium hydroxide (KOH), were used to prepare GO composites. EDC was used as carboxyl groups activating reagent in order to prepare GO-PEG, GO-LMW-PEI, GO-HMW-PEI, GO-PLL-EDC and GO-PArg-EDC. On the other hand, GO-PLL-KOH and GO-PArg-KOH were synthesized by using KOH as epoxy group activating reagent. This is the first time that GO was functionalized with PArg.

The formation and composition between GO and polymers were confirmed by Elementary Analysis (EA), Fourier Transform Infrared (FTIR), Thermo-gravimetric Analysis (TGA) and Scan Electron Microscopy (SEM). Other than that, the ζ-potential and particle size of GO composites were measured. From cytotoxicity studies, we found that functionalized GOs were not toxic to cells if the concentration is less than 100µg/ml. Besides that, these functionalized GOs exhibited good aqueous stability and biocompatibility.

In short, owing to its small size, low cost, large specific area, excellent stability and good biocompatibility, GO is a promising new candidates for biological and medical applications, especially RNA delivery.