The role of hydrophobicity in the disruption of erythrocyte membrane by nanoparticles composed of hydrophobically modified poly(γ-glutamic acid).

Polymeric nanoparticles (NPs) prepared from biocompatible polymers have been studied extensively as carriers for the targeted and controlled delivery of antigens to develop safe and effective vaccines. Especially, the endosomal escape of antigens is essential for the induction of antigen-specific potent immune responses, and the NPs which can control the endosomal escape are urgently required. It has been reported that the hydrophobicity of polymers affected the interactions between the polymer and the membranes, but there have no reports about investigating the effect of the hydrophobicity of the NPs on the membrane disruptive property. In this study, we evaluated the effect of hydrophobicity of NPs on the membrane disruptive property for the first time. We prepared NPs composed of amphiphilic poly(γ-glutamic acid) (γ-PGA) with various grafting degrees of hydrophobic backbone (43-71%), and evaluated the membrane disruptive property. These NPs showed membrane disruptive activity only at the endosomal pH range, and this activity was dependent on the hydrophobicity of γ-PGA. The dependency of the membrane disruptive property on the hydrophobicity of NPs was due to the surface hydrophobicity of them. Our results could provide a guideline for the rational design of amphiphilic polymers as nanoparticle-based vaccine carriers.