Degradation of poly-L-lactide. Part 2: Increased temperature accelerated degradation
Degradation of poly-L-lactide. Part 2: Increased temperature accelerated degradation
复制标题
聚-L-丙交酯的降解。
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
G. Dickson
中科院分区：
文献类型：
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作者：
N. Weir;F. Buchanan;J. Orr;D. Farrar;G. Dickson
摘要聚L丙交酯(PLLA)是一类被认为可生物吸收的聚合物中最重要的成员之一。PLLA的降解是通过聚合物主链中的酯键的水解进行的；然而，在正常的生理环境中，由PLLA制造的整形外科设备完全吸收的时间超过五年。为了评估PLLA在加速时间段内的降解情况，将PLLA颗粒通过压缩模塑处理成拉伸试验样品，然后用环氧乙烷气体(ETO)消毒，并在50°C和70°C的磷酸盐缓冲溶液(PBS)中降解。在回收时，以预定的时间间隔使用程序评估材料的相对分子质量、结晶度、机械强度和热性能。这项研究的结果表明，在50°C和70°C下，体外和体内降解的机制与37°C下观察到的非常相似。所建立的降解模型也证实了在整个降解过程中质量损失、熔融温度和玻璃化转变温度(Tg)与聚合物的相对分子质量的关系。尽管与PLLA的生理降解速度相比，提高温度似乎是加速PLLA降解的合适方法，但人们仍然担心高于聚合物Tg的测试的有效性以及在温度升高时自催化的意义。
Abstract Poly-L-lactide (PLLA) is one of the most significant members of a group of polymers regarded as bioresorbable. The degradation of PLLA proceeds through hydrolysis of the ester linkages in the polymer's backbone; however, the time for the complete resorption of orthopaedic devices manufactured from PLLA is known to be in excess of five years in a normal physiological environment. To evaluate the degradation of PLLA in an accelerated time period, PLLA pellets were processed by compression moulding into tensile test specimens, prior to being sterilized by ethylene oxide gas (EtO) and degraded in a phosphate-buffered solution (PBS) at both 50 °C and 70 °C. On retrieval, at predetermined time intervals, procedures were used to evaluate the material's molecular weight, crystallinity, mechanical strength, and thermal properties. The results from this study suggest that at both 50 °C and 70 °C, degradation proceeds by a very similar mechanism to that observed at 37 °C in vitro and in vivo. The degradation models developed also confirmed the dependence of mass loss, melting temperature, and glass transition temperature (Tg) on the polymer's molecular weight throughout degradation. Although increased temperature appears to be a suitable method for accelerating the degradation of PLLA, relative to its physiological degradation rate, concerns still remain over the validity of testing above the polymer's Tg and the significance of autocatalysis at increased temperatures.