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.

据报道，嵌段共聚物 VIPER（用于内体释放的病毒启发聚合物）是一种有前途的新型 DNA 质粒在体外和体内的递送系统。VIPER 由一个用于缩合核酸的聚阳离子片段以及一个在酸性环境中暴露膜裂解肽蜂毒肽以促进内体逃逸的 pH 敏感片段组成。本研究的目的是研究 VIPER/siRNA 复合物特征，并比较它们的体外和体内市售转染试剂和缺乏蜂毒肽的 VIPER 对照版本的性能。VIPER/siRNA 复合物以各种电荷比进行配制和表征，并显示在培养细胞中有效内化。通过流式细胞术和 qRT-PCR 确认目标 mRNA 敲低，并通过活细胞旋转圆盘显微镜监测敲低的动力学，显示在交付后 4 小时开始敲低。与用乱序序列 siRNA 配制的 VIPER 颗粒进行治疗相比，将用序列特异性 siRNA 配制的 VIPER 颗粒气管内滴注到小鼠肺中导致 GAPDH 的明显更有效的敲低。我们还使用 pH 敏感标签证明，与对照复合物相比，VIPER 颗粒经历的酸性环境较少。总之，在体内导致肺内强大的基因沉默（> 75％敲低）。