Functionalized graphene oxide mediated nucleic acid delivery

We report a simple preparation of linear polyethylenimine-grafted graphene oxide (LP-GO) conjugates and their efficacy to transfer nucleic acids into the mammalian cells. Graphene oxide (GO), with epoxy functions on its surface, was reacted with different amounts of linear polyethylenimine (IPEI), a non-toxic polymer, to obtain three different positively charged LP-GO conjugates (LP-GO-1 to LP-GO-3), capable of interacting with negatively charged nucleic acids (gel retardation assay) and transporting them efficiently into the cells. The results show that these conjugates not only exhibited considerably higher transfection efficiency but also possessed even better cell viability than IPEI. LP-GO-2, the best system in terms of transfection efficiency, showed improved buffering capacity compared to IPEI and provided sufficient stability to bound DNA against DNase I. Further, LP-GO-2 was used for the sequential delivery of GFP specific siRNA, which resulted in similar to 70% suppression of the target gene expression. Intracellular trafficking using fluorescence microscopy revealed that LP-GO-2 conjugate delivered pDNA in the nucleus within 1 h of exposure. The results indicate the prospect of using these conjugates as efficient carriers of nucleic acids for future gene therapy applications. (C) 2012 Elsevier Ltd. All rights reserved.