Increase in Transgene Expression by Pluronic L64-Mediated Endosomal/Lysosomal Escape through Its Membrane-Disturbing Action

For efficient transgene delivery and expression, internalized nucleic acids should quickly escape from cellular endosomes and lysosomes to avoid enzymatic destruction and degradation. Here, we report a novel strategy for safe and efficient endosomal/lysosomal escape of transgenes mediated by Pluronic L64, a neutral amphiphilic triblock copolymer. L64 enhanced the permeability of biomembranes by structural disturbance and pore formation in a concentration- and time-dependent manner. When applied at optimal concentration, it rapidly reached the endosome/lysosome compartments, where it facilitated escape of the transfection complex from the compartments and dissociation of the complex. Therefore, when applied properly, L64 not only significantly increased polyethylenimine- and liposome-mediated transgene expression, but also decreased the cytotoxicity occasioned by transfection process. Our studies revealed the function and mechanism of neutral amphiphilic triblock copolymer as potent mediator for safe and efficient gene delivery.