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Long-Term In Virto Hydrolytic Degradation Behavior and Mechanism of Biodegradable Poly(L-lactic acid)

可生物降解聚L-乳酸的长期体外水解降解行为及机理

基本信息

批准号：
16500291
负责人：
TSUJI Hideto
金额：
$ 2.3万
依托单位：
Toyohashi University of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

The purpose of this project is to elucidate the long-term in vitro hydrolytic degradation behavior and mechanism of PLLA crystalline residues (extended chain crystallites). For this purpose, PLLA crystalline residues were prepared by crystallization of PLLA films and subsequent accelerated hydrolytic degradation at 97℃ for 40 hours and the obtained crystalline residues were hydrolytically degraded at different conditions at pH 7.4 and different temperatures of 37, 50, 70, and 97℃ up to 512 days, at 37℃ at different pH of-0.9, 0.2, 7.4,11.7, and 12.8, and at pH8.6 and 37℃ in the presence of proteinase K. Also, the hydrolytic degradation behavior of L-lactic acid copolymers of poly(L-lactide-co-glycolide) (81:19) [P(LLA-GA)], poly(L-lactide-ε-caprolactone) (77/23) [P(LLA-CL)],and poly(L-lactide-co-D-lactide)] (77:23) (98.8:1.2) [P(LLA-DLA)] and their crystalline residues formed during hydrolytic degradation was monitored. The formation and hydrolytic degradation of the crystalline residu … More es were traced by gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The following results were obtained. (1) For all conditions, the crystalline residues are hydrolytically degraded linearly with degradation time from the chain terminals at the folding surface; (2) The activation energy for hydrolytic degradation (ΔE_h) of the crystalline residues at pH 7.4 was estimated to be 75.2 kJ mol^<-1>. This is much higher than 50.9 kJ mol^<-1> of ΔE_h reported for PLLA in the melt and indicates that higher hydrolytic degradation-resistance of the crystalline residues; (3) Acidic and alkaline conditions as well as high temperature enhanced the hydrolytic degradation of the crystalline residues, whereas proteinase K has no catalytic effect, revealing that the insignificant enzymatic activity of proteinase K for the PLLA chains neighboring on the crystalline regions. (4) The crystalline residues were formed and hydrolytically degraded in P(LLA-GA) and P(LLA-CL) films within the periods of 24 weeks, whereas in the case of PLLA and P(LLA-DLA) (98.8:1.2) films, neither formation nor hydrolytic degradation of crystalline residues took place within the degradation period of 50 weeks. Less

本课题旨在阐明PLLA晶体残基（延伸链晶体）的长期体外水解降解行为及其机理。为此，将PLLA薄膜结晶后，在97℃下加速水解降解40小时，制备出PLLA晶体残基，并在pH 7.4、37、50、70、97℃等不同条件下水解降解512天，在37℃、不同pH值（0.9、0.2、7.4、11.7、12.8）下水解降解，在pH8.6、37℃、蛋白酶k存在下水解降解。对聚（l -乳酸-co-glycolide）（81:19） [P(LLA-GA)]、聚（l -乳酸-ε-己内酯）（77/23）[P(LLA-CL)]和聚（l -乳酸-co- d -乳酸）](77:23)(98.8:1.2)[P(LLA-DLA)]的l -乳酸共聚物的水解降解行为及其在水解降解过程中形成的结晶残基进行了监测。通过凝胶渗透色谱（GPC）和差示扫描量热法（DSC）对结晶残渣的形成和水解降解进行了跟踪。得到了以下结果：(1)在所有条件下，晶体残基在折叠表面的链端随降解时间呈线性水解降解；(2)在pH 7.4条件下，结晶残基水解降解的活化能（ΔE_h）估计为75.2 kJ mol^<-1>。这远远高于熔体中PLLA的50.9 kJ mol^<-1> ΔE_h，表明结晶残留物具有更高的抗水解降解性；(3)酸性和碱性条件以及高温均能促进结晶残基的水解降解，而蛋白酶K则没有催化作用，说明蛋白酶K对邻近结晶区域的PLLA链的酶活性不显著。(4)在P（LLA-GA）和P（LLA-CL）薄膜中，晶体残基在24周内形成并水解降解，而在PLLA和P(LLA-DLA)（98.8:1.2）薄膜中，晶体残基在50周内既没有形成也没有水解降解。少