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In vitro and in vivo delivery of siRNA via VIPER polymer system to lung cells

Feldmann, Daniel P., Cheng, Yilong, Kandil, Rima, Xie, Yuran, Mohammadi, Mariam, Harz, Hartmann, Sharma, Akhil, Peeler, David J., Moszczynska, Anna, Leonhardt, Heinrich, Pun, Suzie H., Merkel, Olivia M.
Journal of controlled release 2018 v.276 pp. 50-58
cations, composite polymers, cultured cells, flow cytometry, gene silencing, lungs, melittin, messenger RNA, mice, microscopy, plasmids, quantitative polymerase chain reaction, reverse transcriptase polymerase chain reaction, small interfering RNA, transfection
The block copolymer VIPER (virus-inspired polymer for endosomal release) has been reported to be a promising novel delivery system of DNA plasmids both in vitro and in vivo. VIPER is comprised of a polycation segment for condensation of nucleic acids as well as a pH-sensitive segment that exposes the membrane lytic peptide melittin in acidic environments to facilitate endosomal escape. The objective of this study was to investigate VIPER/siRNA polyplex characteristics, and compare their in vitro and in vivo performance with commercially available transfection reagents and a control version of VIPER lacking melittin. VIPER/siRNA polyplexes were formulated and characterized at various charge ratios and shown to be efficiently internalized in cultured cells. Target mRNA knockdown was confirmed by both flow cytometry and qRT-PCR and the kinetics of knockdown was monitored by live cell spinning disk microscopy, revealing knockdown starting by 4 h post-delivery. Intratracheal instillation of VIPER particles formulated with sequence specific siRNA to the lung of mice resulted in a significantly more efficient knockdown of GAPDH compared to treatment with VIPER particles formulated with scrambled sequence siRNA. We also demonstrated using pH-sensitive labels that VIPER particles experience less acidic environments compared to control polyplexes. In summary, VIPER/siRNA polyplexes efficiently deliver siRNA in vivo resulting in robust gene silencing (>75% knockdown) within the lung.