Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871, Japan.
J Biomater Sci Polym Ed. 2010;21(3):315-28. doi: 10.1163/156856209X418519.
The efficient cytoplasmic delivery of therapeutic agents is especially important for the induction of a maximal therapeutic effect. Previously, we reported that 200-nm-sized nanoparticles composed of hydrophobically-modified poly(gamma-glutamic acid) (gamma-PGA) showed great potential as protein carriers. Moreover, protein-encapsulated hydrophobic gamma-PGA (gamma-hPGA) nanoparticles efficiently delivered loaded proteins from the endosomes to the cytoplasm in dendritic cells, but the mechanism of the nanoparticle translocation into the cytoplasm remains to be elucidated. In this study, we examined how polymer composition, hydrophobic modification, size, conformation and surface properties of the amphiphilic nanoparticles are related to functional membrane-disruptive activities. To evaluate their potential applications as membrane-disruptive nanoparticles, the nanoparticles were characterized with respect to their hemolytic activity against erythrocytes as a function of pH. The pH-dependent conformation changes of the nanoparticles were studied by Fourier transform infrared (FT-IR) spectroscopy. The gamma-hPGA nanoparticles showed hemolytic activity with decreasing pH from 7 to 5.5, and were membrane-inactive at physiological pH. This activity was dependent on the hydrophobicity of gamma-PGA. The mechanism responsible for the pH-dependent hemolysis by the nanoparticles involved a conformational change of gamma-hPGA and corresponding increase in the surface hydrophobicity. We conclude that gamma-hPGA nanoparticles have significant potential as membrane-disruptive carriers. These results have important implications for the design of endosome-disruptive nanoparticles as drug, protein and DNA delivery systems.
治疗剂的有效细胞质传递对于诱导最大治疗效果尤为重要。以前，我们报道了由疏水性修饰的聚（γ-谷氨酸）（γ-PGA）组成的 200nm 大小的纳米颗粒作为蛋白质载体具有很大的潜力。此外，蛋白质包封的疏水性γ-PGA（γ-hPGA）纳米颗粒可有效地将负载的蛋白质从树突状细胞的内体递送到细胞质中，但纳米颗粒向细胞质的转移机制仍有待阐明。在这项研究中，我们研究了聚合物组成、疏水性修饰、大小、构象和两亲性纳米颗粒的表面性质如何与功能膜破坏活性相关。为了评估它们作为膜破坏纳米颗粒的潜在应用，研究了纳米颗粒对红细胞的溶血活性与 pH 的关系。通过傅里叶变换红外（FT-IR）光谱研究了纳米颗粒的 pH 依赖性构象变化。γ-hPGA 纳米颗粒在 pH 从 7 降低至 5.5 时表现出溶血活性，并且在生理 pH 下是非活性的。这种活性取决于 γ-PGA 的疏水性。纳米颗粒引起 pH 依赖性溶血的机制涉及γ-hPGA 的构象变化和相应的表面疏水性增加。我们得出结论，γ-hPGA 纳米颗粒作为膜破坏载体具有很大的潜力。这些结果对于设计作为药物、蛋白质和 DNA 递送系统的内体破坏纳米颗粒具有重要意义。
