Study on the Improvement of Transfection Efficiency of Antisense Oligonucleotides and Its in Vivo Anti-tumor Effect by Reduction Responsive Micelle Based on Polyethyleneimine

OBJECTIVE To synthesize a polymer PEI-ss-PEG₂₀₀₀-DSPE containing disulfide bond and to prepare as cationic micelle(P-ss-PD) based on branched polyethyleneimine(PEI). To investigate the ability of P-ss-PD micelle to reduce cytotoxicity and improve the transfection efficiency of antisense oligonucleotide(ASO) in human breast cancer cell lines, and to study the anti-tumor effect of P-ss-PD micelle in nude mice.

METHODS PEI-ss-PEG₂₀₀₀-DSPE was synthesized by grafting PEG₂₀₀₀-DSPE onto branched PEI with disulfide bond as a connecting arm. P-ss-PD micelle was prepared by ethanol injection method and P-ss-PD/ASO nanocomplex was obtained by combining P-ss-PD micelle with ASO. The particle size and zeta potential of P-ss-PD/ASO nanocomplex at various mass ratios were determined by laser particle size analyzer. Agarose gel retardation assay was used to investigate the binding degree of P-ss-PD/ASO nanocomplex and determine the optimal mass ratio. At the same time, the reduction responsive ability of P-ss-PD micelle was investigated. The cytotoxicity of P-ss-PD micelle was detected by CCK8 kit. The transfection efficiency of P-ss-PD micelle was investigated by flow cytometry and high content cell imaging analysis system in MDA-MB-231 cells. The anti-tumor effect of P-ss-PD micelle was investigated by tumor-bearing nude mice models.

RESULTS When the mass ratio was 300∶1, the particle size of P-ss-PD/ASO nanocomplex was the smallest and had a good stability. The average particle size was (58.90 ± 4.08)nm, the average zeta potential was (16.80 ± 1.23)mV, and the morphology was uniform spherical. P-ss-PD/ASO nanocomplex had the reduction responsive ability and could release ASO under highly reductive conditions.In vitro, compared with unmodified branched PEI, the cytotoxicity of P-ss-PD micelle was significantly reduced and the transfection efficiency was significantly increased.In vivo, the tumor growth inhibition rate of P-ss-PD/ASO nanocomplex in tumor-bearing nude mice was more than 50%.

CONCLUSION The P-ss-PD micelle prepared in this study is a kind of low toxicity and high transfection efficiency non-viral vector, which has the characteristics of reduction responsive releasing, and shows a promising application in ASO drug delivery.