Baran E T, Ozer N, Hasirci V
University of Minho, Department of Polymer Engineering, Campus de Azurém, 4800-058 Guimarães, Portugal.
J Mater Sci Mater Med. 2002 Dec;13(12):1113-21. doi: 10.1023/a:1021125617828.
In the present study, antileukemic enzyme L-asparaginase (ASNase) was encapsulated into poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanocapsules in order to decrease the immunogenicity and toxicity of the enzyme and to increase its in vivo half life in mice. Nanocapsules were prepared by water-in-oil-in-water approach and each phase was changed systematically. By changing the pH of the w(2) phase to the isolelectric point of L-ASNase, the encapsulation efficiency was increased from 23.7% to 28.0%. Also, modification of ASNase with PEG(2) increased the encapsulation efficiency from 23.7% to 27.9% and protected the enzyme against denaturation. Combination of the various optima enabled a substantial increase in the activity (0.074-0.429 U/mg nanocapsule). The enzyme activity in the blood due to unmodified PHBV nanocapsules dropped to 38% of its initial value 4 h after injection. When the same sample was tested for the enzyme content in the circulation by using the radio-labeled enzyme a much lower enzyme (30% of initial) could be detected after a shorter time (3 h). The PHBV nanocapsules with heparin conjugated on their surface had a longer presence in the circulation than unmodified PHBV nanocapsules. After 6 h, around 50% of the enzyme was still present in the blood. Radioactivity measurements using the same sample showed a sharp decrease in enzyme amount in the circulation in the early stages. However, radioactivity was still detectable at the eighth hour. No adverse effects and symptoms of anaphylaxis were observed upon injection of encapsulated ASNase-PHBV nanocapsules to mice i.v. through the tail vein.
在本研究中，将抗白血病酶L-天冬酰胺酶（ASNase）封装到聚（3-羟基丁酸酯-co-3-羟基戊酸酯）（PHBV）纳米胶囊中，以降低该酶的免疫原性和毒性，并延长其在小鼠体内的半衰期。通过水包油包水法制备纳米胶囊，并系统地改变每个相。通过将w(2)相的pH值改变为L-ASNase的等电点，包封效率从23.7%提高到28.0%。此外，用PEG(2)修饰ASNase可使包封效率从23.7%提高到27.9%，并保护该酶不发生变性。各种最佳条件的组合使活性大幅提高（0.074-0.429 U/mg纳米胶囊）。未修饰的PHBV纳米胶囊注射后4小时，血液中的酶活性降至其初始值的38%。当使用放射性标记的酶对相同样品进行循环中酶含量测试时，在较短时间（3小时）后可检测到低得多的酶（初始值的30%）。表面缀合有肝素的PHBV纳米胶囊在循环中的存在时间比未修饰的PHBV纳米胶囊更长。6小时后，约50%的酶仍存在于血液中。使用相同样品进行的放射性测量显示，循环中酶量在早期阶段急剧下降。然而，在第八小时仍可检测到放射性。通过尾静脉向小鼠静脉注射封装的ASNase-PHBV纳米胶囊后，未观察到过敏反应的不良反应和症状。
