PGLA热降解性能的研究

使用热重分析仪（TG）对聚乙丙交酯（PGLA）与聚乙交酯（PGA）的热降解性能进行测试,并通过Kissinger、Flynn-wan-ozawa和Friedman 3种方法计算其降解过程中的活化能Ea。结果表明,PGLA的热稳定性较PGA更好,3种方法均能较好的分析其降解过程,当使用Flynn-wan-ozawa法拟合时,其线性相关性较好。     

Optimization of Formulation Variables to Increase Antigen Entrapment in PLGA Particles

Efficient antigen entrapment is a key factor in preparation of poly (lactide-co-glycolide) acid (PLGA) vaccine formulations when the antigen is of short supply. This study presents a systematic approach in the testing of formulation variables with the objective to increase antigen entrapment in particles when the antigen stock concentration was low. Some of the experimental variables tested were poly (vinyl) alcohol (PVA) concentration in the inner (W₁) and outer (W₂) aqueous phase, W₁/oil (O) phase ratio and choice of organic solvent. The double emulsion solvent evaporation technique was applied to prepare PLGA particles with sonication as the emulsifying force. To measure antigen entrapment efficiency, the antigen (bovine serum albumin, BSA) was isotope labeled with ¹²⁵iodine (¹²⁵I). Our results demonstrated that a low PVA concentration in the inner aqueous (W₁) phase was beneficial to achieve a high encapsulation efficiency of antigen. On the contrary, in the outer aqueous (W₂) phase, a high PVA concentration favored antigen entrapment. We also demonstrated that decreasing the W₁ to O/polymer ratio contributed to increased entrapment efficiency. Testing different organic solvents (ethyl acetate, dichloromethane and chloroform), either alone or in combination, revealed that using chloroform as solvent resulted in the highest encapsulation of antigen and the highest production yield. Some of the results presented in this work are in disagreement with well-established formulation variables from previous studies.     

125I籽源照射对壳聚糖涂层的聚乙丙交酯载体支架体外降解性能的影响

研究125I籽源持续低剂量率照射对壳聚糖涂层的聚乙丙交酯(Poly(glycolide-co-lactide),PGLA)薄层支架体外降解性能的影响。在离体条件下,模拟人体环境采用磷酸盐缓冲液(Phosphatebufferedsolution,PBS)作为降解介质,125I籽源单粒表观活度为29.6MBq,在薄层支架中5粒125I籽源按一定规律排布。采用质量损耗、弹性回复率测试和扫描电镜观察等方法来评价PGLA薄层支架的体外降解性能。照射后第2周,PGLA薄层支架的质量损耗仅减少了10%左右,弹性保持率维持在60%以上,材料纤维结构保持完好,降解行为不明显;照射第4周时,材料受照剂量最高点处的累积剂量达2.2×103Gy,PGLA薄层支架质量损耗率未超过50%,弹性保持率仍有36%,扫描电镜观察显示,部分材料纤维开始出现裂纹和缝隙,较对照组明显,表明125I籽源持续低剂量率照射4周能使PGLA薄层支架降解速率有所加快,但仍维持了约59%质量和一定的弹性,形态结构保持较好,能有效维持125I籽源的空间分布。     

热拉伸对PGLA(90/10)纤维降解性能的影响

利用热拉伸获得不同性能与结构形态的PGLA(GA/LA摩尔比=90/10)纤维,并进行体外降解实验。在降解过程中,采用DSC、傅里叶红外光谱、扫描电镜等测试手段对PGLA(90/10)纤维的性能与形态变化进行研究。结果表明,热拉伸显著改变PGLA(90/10)纤维的降解特征。     

PGLA纤维成形过程中的结品性能

采用熔融纺丝法纺制聚乙丙交酯（PGLA）纤维,运用X-射线衍射、DSC等方法对PGLA纤维拉伸和定形过程中结晶性能的变化进行测试和研究。实验表明,拉伸比、拉伸温度和定形温度是常用的3个工艺参数,它们对纤维结晶度有着最直接的影响。制备的PGLA纤维具有良好的力学性能,在60℃下拉伸5．5倍,强度达5．2cN／dtex,断裂伸长为24％,可以满足医用缝合线的力学性胄皂要求。     

医用纤维材料PGLA910的直接熔融聚合法研究

分别以D,L-乳酸(D,L-LA)、L-乳酸(L-LA)为原料,与乙醇酸(GA)通过熔融聚合法进行共聚,在催化剂SnCl2用量0.5％(wt)、反应温度165℃、反应压力70Pa、反应时间10h的条件下直接合成了生物降解的医用纤维材料聚乙醇酸-乳酸(90/10)(PGLA 910)。产品用IR、DSC、X-射线衍射等进行了表征,并与乙交酯开环聚合二步法合成的PGLA910进行了比较。直接熔融聚合产品的结晶度接近于二步法,D,L-PGLA910的结晶度和微晶尺寸比L型的大。直接熔融共聚工艺流程短、简单易行、耗时少、成本低,有利于医用纤维材料PGLA910的规模开发。     

熔融聚合法直接合成生物降解材料PGLA50/50

以等摩尔乙醇酸、L-乳酸为原料 ,通过熔融聚合法直接合成生物降解材料聚乙醇酸 -乳酸 (PGLA50 / 50 )。当在 1 65℃、70Pa下熔融聚合 1 0h ,以质量分数为 0 .5 %的氯化亚锡为催化剂时 ,产物特性黏数最高可达 0 .1 993dL/g。