Zheng Ai-Ping, Wang Jian-Cheng, Lu Wan-Liang, Zhang Xuan, Zhang Hua, Wang Xue-Qing, Zhang Qiang
Department of Pharmaceutics, School of Pharmaceutical Sciences, Peking University, Beijing, China.
J Nanosci Nanotechnol. 2006 Sep-Oct;6(9-10):2936-44. doi: 10.1166/jnn.2006.451.
Thymopentin, a potent immunomodulating drug, was incorporated into pH-sensitive chitosan nanoparticles prepared by ionic gelation of chitosan with tripolyphosphate anions and then coated with Eudragit S100 to improve the stability and the oral bioavailability. Nanoparticles particle size and zeta potential were measured by photo correction spectroscopy and laser Dopper anemometry. Its morphology was examined by environment scan electron microscope. The encapsulation efficiency and the release in vitro were determined by HPLC. Enzymatic stabilization was expressed by the enzymatic degradation of aminopeptidase. Biological activity of TP5 loaded in nanoparticles was assayed by lymphocyte proliferation test in vitro and the immune function (CD4+/CD8+) of irradiated rat in vivo. The results obtained demonstrated that the average sizes of pH-sensitive chitosan nanoparticles were 175.6 +/- 17 nm, the zeta potential was 28.44 +/- 0.5 mV and the encapsulation efficiency was 76.70 +/- 2.6%. The cumulative release percentages of thymopentin from the pH-sensitive nanoparticles were 24.65%, 41.01%, and 81.44% incubated in different medium, 0.1 N HCl, pH 5.0 PBS, and pH 7.4 PBS, respectively. The pH-sensitive chitosan nanoparticles could efficiently protect TP5 from enzymatic degradation and prolong the degradation half-time of TP5 from 1.5 min to 15 min. It was demonstrated from the lymphocyte proliferation test that the nanoparticle-encapsulated TP5 still kept its biological activity. In immunosuppression rats, the lowered T-lymphocyte subsets values were significantly increased and the raised CD4+/CD8+ ratio was evidently reduced. These results indicated that pH-sensitive chitosan nanoparticles may be used as the vector in oral drug delivery system for TP5.
胸腺五肽是一种有效的免疫调节药物，它被载入通过壳聚糖与三聚磷酸阴离子进行离子凝胶化制备的pH敏感壳聚糖纳米粒中，然后用Eudragit S100包衣以提高稳定性和口服生物利用度。通过光校正光谱法和激光多普勒风速测定法测量纳米粒的粒径和zeta电位。用环境扫描电子显微镜检查其形态。通过高效液相色谱法测定包封率和体外释放情况。通过氨肽酶的酶促降解来表示酶稳定性。通过体外淋巴细胞增殖试验和体内照射大鼠的免疫功能（CD4+/CD8+）来测定载入纳米粒中的TP5的生物活性。所获得的结果表明，pH敏感壳聚糖纳米粒的平均粒径为175.6±17nm，zeta电位为28.44±0.5mV，包封率为76.70±2.6%。胸腺五肽从pH敏感纳米粒中的累积释放率分别为：在0.1N HCl、pH 5.0 PBS和pH 7.4 PBS等不同介质中孵育时，依次为24.65%、41.01%和81.44%。pH敏感壳聚糖纳米粒可以有效地保护TP5不被酶促降解，并将TP5的降解半衰期从1.5分钟延长至15分钟。淋巴细胞增殖试验表明，纳米粒包封的TP5仍保持其生物活性。在免疫抑制大鼠中，降低的T淋巴细胞亚群值显著升高，升高的CD4+/CD8+比值明显降低。这些结果表明，pH敏感壳聚糖纳米粒可作为TP5口服给药系统的载体。
