Chitosan modified by γ-ray-induced grafting of poly(tributyl-(4-vinylbenzyl)phosphonium) as a biosafe and high-efficiency gene carrier

The development of gene carriers with high delivery efficiency and enough biosafety to replace the current viral vectors and cationic liposomes has long been a key project to achieve the practical application of gene therapy. As an abundant natural polymer, chitosan (CS) possesses incomparably high biocompatibility. However, when it is used as a gene carrier, the gene transfection efficiency is rather disappointing. Herein, we prepared a novel chitosan derivative, poly(tributyl-(4-vinylbenzyl)phosphonium)-grafted CS (CS-P), via γ-ray radiation-induced grafting copolymerization of tributyl-(4-vinylbenzyl)phosphonium in an acidic solution of CS. The CS-P could combine with pEGFP through a complex coacervation method to form pEGFP-loaded CS-P complex particles with a size of about 150 nm and a high positive zeta potential of 41.7 ± 6.1 mV. Agarose gel electrophoresis and an MTT assay show that the pEGFP-loaded CS-P particles have excellent biosafety, superior to pEGFP-loaded unmodified CS particles. In vitro and in vivo gene transfection experiments based on HeLa cells confirmed that pEGFP loaded into CS-P particles exhibits much higher gene transfection efficiency than that loaded into unmodified CS. This work provides not only a new way to modify CS with quaternary phosphonium, but also a useful and feasible way to obtain new CS-based gene vectors with high gene transfection efficiency and biosafety for potentially practical clinic applications.