Efficient targeted pDNA/siRNA delivery with folate-low-molecular-weight polyethyleneimine-modified pullulan as non-viral carrier.

Folate receptor (FR)-mediated gene/short interfering RNA (siRNA) targeting shows advantage for the delivery of gene/siRNA into specific FR-overexpressing cancer cells. In this study, the non-targeted gene vector P-PEI was synthesized by grafting low-molecular-weight (1kDa) branched polyethyleneimine (PEI) to succinylated pullulan, and the targeted gene vector P-PEI-FA was synthesized by coupling the carboxyl of folate (FA) to the amino of PEI. Gel electrophoresis retardation assay demonstrated that both P-PEI and P-PEI-FA can efficiently wrap pDNA and siRNA with electrostatic interaction at N/P ratios higher than 1.56 and can protect pDNA from degradation by DNase I and serum. Compared with PEI/pDNA, P-PEI/pDNA and P-PEI-FA/pDNA showed lower cytotoxicity against different cells. Under serum-containing conditions, compared with Lipofamine 2000/DNA and Lipofamine2000/siRNA, P-PEI-FA/DNA at N/P ratio of 6.25 displayed higher gene transfection efficiency, whereas P-PEI-FA/siRNA at N/P ratio of 12.5 demonstrated better enhanced gene silencing effect. P-PEI-FA/siRNA can also deliver FAM-labeled siRNA to endosomes and escape. Moreover, the gene transfection and silencing effects of P-PEI-FA were higher than those of P-PEI, and were dependent on the dose of FA in FR(+) HeLa cells. Thus, P-PEI-FA can assist DNA or siRNA targeting to FR-overexpressing cells, and the uptake pathway of P-PEI-FA/siRNA was FR-mediated endocytosis. These results indicate that P-PEI-FA is a potential candidate for safe and targeted gene delivery applications.