^(32)P放射性活度对^(32)P-磷酸铬-聚L-乳酸缓释粒子降解特性影响的初步研究

Effect of the radioactivity of ^(32)P on the biodegradable characteristics of ^(32)P-chromic phosphate-poly(L-lactide) seeds

目的:探讨不同放射性比活度32P对32P-磷酸铬-聚L-乳酸[32P-chromic phosphate-poly(L-lactide),32P-CP-PLLA]缓释粒子体内外溶蚀降解、放射性释出特性的影响。方法:将放射性比活度呈倍比增加的32P-CP-PLLA缓释粒子(记为S1-5)分别置于胎牛血清、生理盐水和右旋糖酐中(分别记为X、Y、Z组),另取S1-5型32P-CP-PLLA粒子分别植入肝癌HepG2实体瘤内,分别测定不同时间点粒子溶蚀降解失重率、放射性释出率及电镜下超微结构变化。结果:在胎牛血清(无菌环境下)、生理盐水及右旋糖酐中,相同时间点S1-5粒子放射性释出率增加,以32 d及其以后尤为显著,且相同时间点粒子放射性释出率增加呈一定的倍数关系;粒子肝癌内植入后,粒子降解失重率和放射性释出率随粒子放射性活度增加呈一致性增加,随时间变化的趋势同体外实验;胎牛血清(一般环境)中,粒子放射性释出较体内外其它组均快,差异以64 d显著,电镜下可见粒子内菌体存在。结论:32P作为一种纯β射线发射体,可能是32P-CP-PLLA粒子体内外降解和放射性释出的主要调节因素,而细菌或相关产物可能也是影响其降解的因素之一。

Objective：To investigate the influence of 32P on the biodegradation and radioactivity release rate of 32P-chromic phosphate-poly（L-lactide）（32P-CP-PLLA） seed.Methods：32P-CP-PLLA seeds with increased radioactivity and specific radioactivity were prepared（noted as S1-5） and their biodegradation,weight loss,radioactivity release rate and ultrastructure changes were investigated in different releasing medium such as fetal bovine serum,saline and dextran（noted as X,Y,Z）,and after intratumor implantion.Results：32P-CP-PLLA seeds with increasing radioactivity were demonstrated increased radiation release rate at same time points,especially since day 32 and the increase seems corresponding with the change of the radioactivity of seed.And the increase of biodegradational weight loss matched with the increase of radiation release rate after intratumor implantation.The radiation release rate was much faster in the fetal bovine serum（sterile environment） than that in other medium and in vivo,and bacteria were found in the seeds by electron microscope.Conclusion： 32P may serve as one important modulator of the biodegradation and radiation release rate of 32P-CP-PLLA seed,and bacteria with possible secreting matters may also influence the biodegradation of PLLA.