Shah Nihar M, Pool Michael D, Metters Andrew T
Department of Bioengineering and Department of Chemical and Biomolecular Engineering, Clemson University, Clemson, South Carolina 29634, USA.
Biomacromolecules. 2006 Nov;7(11):3171-7. doi: 10.1021/bm060339z.
Triblock copolymers of functionalized poly(lactic acid)-b-poly(ethylene glycol)-b-poly(lactic acid) (PLA-b-PEG-b-PLA) have been widely investigated as precursors for fabricating resorbable polymeric drug delivery vehicles and tissue engineering scaffolds. Previous studies show degradation and erosion behavior of PLA-b-PEG-b-PLA hydrogels to rely on macromer chemistry as well as structural characteristics of the cross-linked networks. In this research, the degradation kinetics of diacrylated PLA-b-PEG-b-PLA copolymers as soluble macromers and cross-linked gels are directly compared as a function of macromer concentration, buffer pH, and ionic strength. The pseudo first-order rate constants for degradation of soluble macromers increase with water concentration and show a minimum at intermediate pH values, but are insensitive to ionic strength. The degradation rate constants for covalently cross-linked gels display a greater sensitivity to local water concentration and a minimum at lower pH values than corresponding soluble macromers. In addition, ionic strength significantly affects the rate of gel degradation due to the direct correlation between the degree of network ionization and gel water content.
功能化聚乳酸- b -聚乙二醇- b -聚乳酸（PLA - b - PEG - b - PLA）三嵌段共聚物作为制备可吸收聚合物药物递送载体和组织工程支架的前体已被广泛研究。先前的研究表明，PLA - b - PEG - b - PLA水凝胶的降解和侵蚀行为依赖于大分子单体化学以及交联网络的结构特征。在本研究中，直接比较了作为可溶性大分子单体和交联凝胶的双丙烯酸化PLA - b - PEG - b - PLA共聚物的降解动力学，作为大分子单体浓度、缓冲液pH值和离子强度的函数。可溶性大分子单体降解的伪一级速率常数随水浓度增加而增加，在中间pH值时出现最小值，但对离子强度不敏感。共价交联凝胶的降解速率常数对局部水浓度的敏感性更高，且在比相应可溶性大分子单体更低的pH值时出现最小值。此外，由于网络电离程度与凝胶含水量之间的直接相关性，离子强度显著影响凝胶的降解速率。
