Akagi Takami, Higashi Mariko, Kaneko Tatsuo, Kida Toshiyuki, Akashi Mitsuru
Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871, Japan.
Biomacromolecules. 2006 Jan;7(1):297-303. doi: 10.1021/bm050657i.
Amphiphilic graft copolymers consisting of poly(gamma-glutamic acid) (gamma-PGA) as the hydrophilic backbone and L-phenylalanine ethylester (L-PAE) as the hydrophobic side chain were synthesized by grafting L-PAE to gamma-PGA. The nanoparticles were prepared by a precipitation method, and about 200 nm-sized nanoparticles were obtained due to their amphiphilic properties. The hydrolytic and enzymatic degradation of these gamma-PGA nanoparticles was studied by gel permeation chromatography (GPC), scanning electron microscopy (SEM), dynamic light scattering (DLS) and (1)H NMR measurements. The hydrolysis ratio of gamma-PGA and these hydrophobic derivatives was found to decrease upon increasing the hydrophobicity of the gamma-PGA derivates. The pH had an effect on the hydrolytic degradation of the polymer. The hydrolysis of the polymer could be accelerated by alkaline conditions. The degradation of the gamma-PGA backbone by gamma-glutamyl transpeptidase (gamma-GTP) resulted in a dramatic change in nanoparticle morphology. With increasing time, the gamma-PGA nanoparticles began to decrease in size and finally disappeared completely. Moreover, the gamma-PGA nanoparticles were degraded by four different enzymes (Pronase E, protease, cathepsin B and lipase) with different degradation patterns. The enzymatic degradation of the nanoparticles occurred via the hydrolysis of gamma-PGA as the main chain and L-PAE as the side chain. In the case of the enzymatic degradation of gamma-PGA nanoparticles with Pronase E, the size of the nanoparticles increased during the initial degradation stage and decreased gradually when the degradation time was extended. Nanoparticles composed of biodegradable amphiphilic gamma-PGA with reactive function groups can undergo further modification and are expected to have a variety of potential pharmaceutical and biomedical applications, such as drug and vaccine carriers.
通过将L-苯丙氨酸乙酯（L-PAE）接枝到聚（γ-谷氨酸）（γ-PGA）上，合成了以聚（γ-谷氨酸）（γ-PGA）为亲水性主链、L-苯丙氨酸乙酯（L-PAE）为疏水性侧链的两亲性接枝共聚物。采用沉淀法制备纳米颗粒，由于其两亲性，获得了尺寸约为200 nm的纳米颗粒。通过凝胶渗透色谱（GPC）、扫描电子显微镜（SEM）、动态光散射（DLS）和（1）H NMR测量研究了这些γ-PGA纳米颗粒的水解和酶促降解。发现随着γ-PGA衍生物疏水性的增加，γ-PGA及其疏水性衍生物的水解率降低。pH值对聚合物的水解降解有影响。碱性条件可加速聚合物的水解。γ-谷氨酰转肽酶（γ-GTP）对γ-PGA主链的降解导致纳米颗粒形态发生显著变化。随着时间的增加，γ-PGA纳米颗粒尺寸开始减小，最终完全消失。此外，γ-PGA纳米颗粒被四种不同的酶（链霉蛋白酶E、蛋白酶、组织蛋白酶B和脂肪酶）以不同的降解模式降解。纳米颗粒的酶促降解是通过γ-PGA作为主链和L-PAE作为侧链的水解发生的。在用链霉蛋白酶E酶促降解γ-PGA纳米颗粒的情况下，纳米颗粒尺寸在初始降解阶段增加，降解时间延长时逐渐减小。由具有反应性功能基团的可生物降解两亲性γ-PGA组成的纳米颗粒可以进行进一步修饰，有望具有多种潜在的药物和生物医学应用，如药物和疫苗载体。
