Hydrothermal Reduction of Polyethylenimine and Polyethylene Glycol Dual-Functionalized Nanographene Oxide for High-Efficiency Gene Delivery

Abstract

In this study, a physiologically stable dual-polymer-functionalized reduced nanographene oxide (nrGO) conjugate (PEG-nrGO-PEI, RGPP) with high efficiency of gene delivery is successfully synthesized through mixing PEGylated nanographene oxide (PEG-nGO, GP) and polyethylenimine (PEI, 25 kDa) solution under 80 °C for 2 h. This hydrothermal reduction of GP during PEIylation promotes the nucleophilic reaction between the amino moieties of PEI and the epoxy groups (or carboxylic groups) in GP and then forms C-NH- groups (or NH-CO groups) to covalently connect PEI and GP, which makes the RGPP nanocomposite more stable in physiological environments and has superior gene transfection efficiency compared with the nonhydrothermally reduced PEG-nGO/PEI conjugate (GPP) obtained by mixing GP and PEI under 20 °C for 2 h. Moreover, 808 nm laser irradiation (2 W/cm²) for 25 min increases ∼1.5-fold of gene transfection efficiency for RGPP but does not increase the gene transfection efficiency of GPP. Finally, RGPP is also able to efficiently deliver functional plasmid GFP-Bax (pGFP-Bax), exhibiting ∼43% of transfection efficiency in HepG2 cells. Collectively, the RGPP developed here is a highly efficient nanocarrier for gene delivery, and this work encourages further explorations of developing functionalized reduced nano-GO for high-efficiency gene therapy.

Keywords: gene delivery; hydrothermal reduction; nanographene oxide; photothermal effect; polyethylene glycol; polyethylenimine.