Schmitt E A, Flanagan D R, Linhardt R J
Division of Pharmaceutics, College of Pharmacy, University of Iowa, Iowa City 52242.
J Pharm Sci. 1993 Mar;82(3):326-9. doi: 10.1002/jps.2600820322.
Poly(D,L-lactide-co-glycolide, 50:50) samples of similar molecular weight were obtained from three commercial sources and were characterized by gel permeation chromatography, differential scanning calorimetry, X-ray powder diffraction, viscometry, and proton nuclear magnetic resonance spectroscopy. Pellets were prepared by melt-pressing spray-dried polymer with a 4-mm standard concave punch and die set and a thermostated holder of original design. Amaranth (5% w/w) was incorporated in pellets used for release studies. Degradation and release studies were conducted at 37 degrees C in pH 7.2 phosphate buffered saline. The molecular weights of all polymers were found to decrease continuously after exposure to phosphate buffered saline. All polymers showed two distinct regions of molecular weight decrease. Mass loss experiments for all polymers resulted in sigmoidal curves typical of polymers undergoing bulk hydrolysis. The onset of mass loss (defined as 10% mass loss) was found to differ by as much as 6 days among the three polymers studied. The release studies showed an initial burst of release followed by a period of 15-25 days during which little or no dye was released. A second phase of release followed, lasting approximately 10 days, until all dye was released. The time at which release began slightly preceded the onset of mass loss.
从三个商业来源获得了分子量相似的聚（D，L-丙交酯-共-乙交酯，50:50）样品，并通过凝胶渗透色谱法、差示扫描量热法、X射线粉末衍射法、粘度测定法和质子核磁共振光谱法对其进行了表征。通过使用4毫米标准凹形冲头和模具以及原始设计的恒温支架对喷雾干燥的聚合物进行熔融压制来制备粒料。将苋菜红（5%w/w）加入用于释放研究的粒料中。在37℃的pH 7.2磷酸盐缓冲盐水中进行降解和释放研究。发现所有聚合物在暴露于磷酸盐缓冲盐水后分子量持续下降。所有聚合物均显示出两个不同的分子量下降区域。所有聚合物的质量损失实验均得到了典型的聚合物本体水解的S形曲线。在所研究的三种聚合物中，质量损失的起始点（定义为10%质量损失）相差多达6天。释放研究表明，最初有一个释放突增期，随后是15 - 25天的时间段，在此期间几乎没有或没有染料释放。接着是第二阶段的释放，持续约10天，直到所有染料都被释放。释放开始的时间略早于质量损失的起始点。
