甲壳素对左旋聚乳酸体内降解性能的影响

Effect of chitin on in vivo degradation of poly-L-lactic acid

目的:探讨甲壳素对左旋聚乳酸体内降解性能的影响。方法:实验于2004-03/12在南方医院动物中心进行。材料的合成及检测在中山大学高分子材料研究所完成。将甲壳素以质量8/100的质量比共混入左旋聚乳酸制成条状,兔右侧脊柱旁背部肌肉内随机植入2条左旋聚乳酸/甲壳素,左侧植入左旋聚乳酸。于术后4,8,12,20,24,26周随机各处死3只兔子,取出植入条作功能测试。定期观察粘均分子量、失重率变化以及大体形态和扫描电镜下的微观形态,评价甲壳素在体内对左旋聚乳酸降解性能的影响。结果:18只兔子均进入结果分析。①大体形态观察结果:聚乳酸降解4周即出现白垩色变化,随着时间的增加,变得不透明,质脆,中间出现孔隙,36周后崩解成颗粒状,且部分溶于水;聚乳酸-甲壳素降解早期即变软,断裂,最后表面出现点窝状缺损。②扫描电镜显示植入前两组材料截面均匀致密,聚乳酸-甲壳素组可见甲壳素颗粒分布于聚乳酸中,结合紧密,随着植入时间的延长,首先于甲壳素颗粒周围出现间隙,然后聚乳酸间出现缝隙;聚乳酸组降解12周材料边缘仍致密,但中间出现孔隙,24周材料结构完全松解。③聚乳酸的粘均分子量在降解的前8周下降较快,半衰期只有4周,12周时降解90%以上;而聚乳酸-甲壳素的粘均分子量半衰期延至20周。④聚乳酸的失重率半衰期为24周,36周时失重61%;聚乳酸-甲壳素的失重率到观察结束时(36周)仍不到25%。结论:甲壳素可明显减慢左旋聚乳酸的降解速率。

AIM： To probe into the effects of chitin on in vivo degradation of poly-L-lactic acid （PLLA）. METHODS： The study was conducted in the Animal Center of Nanfang Hospital between March and December 2004. The synthesis and inspection of materials were accomplished in the Institute of Polymer ScienCe of Sun Yet-set University. The chitin was made into strips by mixing with the PLLA at 8/100, and two strips of PLLA/chltin were implanted in the muscle of back near the right lateral vertebral column of rabbits, and the left side was implanted of the PLLA. Three rabbits that randomly selected each time were executed respectively at 4, 8, 12, 20, 24 and 26 weeks after operation, and the implanted strips were taken out to determine. Thechanges of viscosity-average molecular weight, weightlessness rate, general status and the micro status under scanning electron microscope were observed regularly. The effects of degradation of PLLA on chitin were evaluated. RESULTS： A total of 18 rabbits were involved the analysis of results. ①Ohservation on general status： On the 4th week of degradation, PLLA rods turned to be whitened; and were more and ＂more opaque with the time increasing, which were brittle with ventage appeared in the middle. Thirty-six weeks later, they were broken into granules, and partial could dissolve in the water. The ploylactic acid-chitin were softened and broken in the early stage of degradation, and there were dot-like deficits on the surface at last.②The scanning electron microscope indicated that the cross- sections of materials in both groups before implantation were dense and even, and in the PLLA there were distribution of chitin particles in the PLLA-chitin group, which were densely integrated. With the time increasing, gaps firstly appeared in the periphery of chitin particles, which were then could be found in the PLLA. Those of the PLLA group in the borderline of materials on the 12th week of degradation were still dense, while there were gaps in the middle. The structure of materials were completely loosened on the 24th week.③The degradation of v iscosity-average molecular weight was rapid in the previous 8 weeks, and was only 4 weeks in the half life. The degradation on the 12th week was greater than 90%. While the viscosity-average molecular weight of PLLA-chitin in half llfe was prolonged to 20 weeks. ④ The rate of weightlessness of PLLA in half life was 24 weeks, which was 61% on the 36th week. It was less than 25% at the end of observation （36th week）. CONCLUSION： Chitin can significantly slow the speed of degradation of PLLA.