低聚左旋聚乳酸的降解性能研究

Study on the degradation property of poly-L-lactic acid

目的研究自制低聚左旋聚乳酸(poly-L-lacticacid,PLLA)在体内、体外的降解性。方法通过PBS溶液体外水解试验和动物体内植入试验,定期观察试样的形态、失重率、分子量和弯曲强度的变化,评价自制左旋聚乳酸的降解性能。结果体外降解的pH值前12周基本维持稳定,12周后虽明显下降,但降幅最大不超过0.8个单位;两组的粘均分子量在前12周下降较快,达50%以上,其后降解减慢,24周粘均分子量降解90%以上(剩余约3kDa);失重率前12周则基本没变化,其后迅速增加,体外降解36周时失重率为32%,体内降解24周时失重率接近25%,36周时达61%;弯曲强度4周时只维持1/3左右,8周时体外组不到初始1/4,体内组多已断裂;体内降解36周后材料崩解成颗粒状,部分溶解于水,体外组外形保持完整,但质脆易碎。结论自制PLLA的体内、体外降解速度无显著性差异,符合简单水解的规律,作为骨修复材料,机械性能的维持有待提高。

Objective To study the degradation properties of poly-L-lactic acid (PLLA) in vitro and in vivo. Methods A hydrolysis test was performed in PBS in vitro, and PLLA rods were implanted in 18 rabbits' bodies for in vivo study. Degradation was studied via mass loss ratio, molecular weight changes, tensile testing, and visual observation. Results The pH in vitro mainteined stable in 12 weeks, and significantly decreased after 12 weeks with a decrease less than 0.8 unit. The molecular weight decreased by 50% in 12 weeks and by 90% 24 weeks. The mass-loss stayed stable in 12 weeks, and subseqnently increased significantly. The mass-loss ratio at 36 weeks was 32% in vitro with brittle rods and 61% in vivo with fragments. The mechanical strength sharply decreased by 1/3 in 4 weeks and in by 1/4 8 weeks. Conclusion Both in vitro and in vivo, degradation proceeds at the same rate and follows the general sequence of hydrolysis.