Ruiz J M, Busnel J P, Benoît J P
Laboratoire de Pharmacie Galénique et Biopharmacie, UA CNRS 1218, Université de Paris-Sud, Chatenay-Malabry, France.
Pharm Res. 1990 Sep;7(9):928-34. doi: 10.1023/a:1015945806917.
The phase separation of fractionated poly(DL-lactic acid-co-glycolic acid) copolymers 50/50 was determined by silicone oil addition. Polymer fractionation by preparative size exclusion chromatography afforded five different microsphere batches. Average molecular weight determined the existence, width, and displacement of the "stability window" inside the phase diagrams, and also microsphere characteristics such as core loading and amount released over 6 hr. Further, the gyration and hydrodynamic radii were measured by light scattering. It is concluded that the polymer-solvent affinity is largely modified by the variation of average molecular weights owing to different levels of solubility. The lower the average molecular weight is, the better methylene chloride serves as a solvent for the coating material. However, a paradoxical effect due to an increase in free carboxyl and hydroxyl groups is noticed for polymers of 18,130 and 31,030 SEC (size exclusion chromatography) Mw. For microencapsulation, polymers having an intermediate molecular weight (47,250) were the most appropriate in terms of core loading and release purposes.
通过添加硅油测定了50/50的聚（DL-乳酸-共-乙醇酸）共聚物的相分离。通过制备型尺寸排阻色谱法进行聚合物分级得到了五个不同的微球批次。平均分子量决定了相图中“稳定窗口”的存在、宽度和位移，以及微球特性，如包芯量和6小时内的释放量。此外，通过光散射测量了回转半径和流体动力学半径。得出结论，由于溶解度水平不同，平均分子量的变化极大地改变了聚合物与溶剂的亲和力。平均分子量越低，二氯甲烷作为包衣材料的溶剂效果越好。然而，对于18,130和31,030 SEC（尺寸排阻色谱法）Mw的聚合物，由于游离羧基和羟基的增加，出现了自相矛盾的效应。对于微囊化，就包芯量和释放目的而言，具有中等分子量（47,250）的聚合物是最合适的。
