Cationic polymer brush grafted-nanodiamond via atom transfer radical polymerization for enhanced gene delivery and bioimaging

A novel cationic nanodiamond-polymer brush was synthesized by 2-bromoisobutyrate-modified nanodiamond (ND) surface-initiated atomic transfer radical polymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA). Elemental analysis, FTIR, HRTEM, TGA and zeta potential analysis were used to confirm the successful synthesis of ND-polymer brushes. It was shown that the ND-brushes were capable of condensing plasmid DNA into stable nanoparticles, protecting DNA from enzyme degradation. Transfection studies demonstrated that the ND-brushes could not only efficiently deliver plasmids into COS-7 cells, but also mediate higher expression than PEI25k with lower cytotoxicity. The green fluorescence of ND-brushes could also be detected by laser scanning confocal microscopy, making the nanodiamond-polymer brushes an excellent multifunctional gene vector with not only high transfection efficiency but allowing for bioimaging.