Department of Chemistry, College of Science, Rikkyo University , 3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo 171-8501, Japan.
School of Chemical Engineering, Fuzhou University , No. 2 Xueyuan Rd, Minhou Country, Fuzhou 350116, People's Republic of China.
Biomacromolecules. 2017 Apr 10;18(4):1281-1292. doi: 10.1021/acs.biomac.7b00016. Epub 2017 Mar 28.
Although poly(l-lactic acid) (PLLA) is reputed to be biodegradable in the human body, its hydrophobic nature lets it persist for ca. 5.5 years. This study demonstrates that biologically safe lactide copolymers, poly(aspartic acid-co-l-lactide) (PAL) and poly(malic acid-co-l-lactide) (PML), dispersed in the PLLA function as detonators (triggers) for its hydrolytic degradation under physiological conditions. The copolymers significantly enhance hydrolysis, and consequently, the degradation rate of PLLA becomes easily tunable by controlling the amounts of PAL and PML. The present study elucidates the effects of uniaxial drawing on the structural development, mechanical properties, and hydrolytic degradation under physiological conditions of PLLA blend films. At initial degradation stages, the mass loss was not affected by uniaxial drawing; however, at late degradation stages, less developed crystals as well as amorphous chains were degradable at low draw ratio (DR), whereas not only highly developed crystals but also the oriented amorphous chains became insensitive to hydrolysis at high DR. Our work provides important molecular level results that demonstrate that biodegradable materials can have superb mechanical properties and also disappear in a required time under physiological conditions.
尽管聚（L-乳酸）（PLLA）在人体中被认为是可生物降解的，但它的疏水性使其大约 5.5 年才能被降解。本研究表明，生物安全的丙交酯共聚物，聚（天冬氨酸-co-L-乳酸）（PAL）和聚（苹果酸-co-L-乳酸）（PML），分散在 PLLA 中，可以在生理条件下作为其水解降解的引爆剂（触发器）。这些共聚物显著增强了水解作用，因此，通过控制 PAL 和 PML 的含量，可以很容易地调节 PLLA 的降解速率。本研究阐明了单向拉伸对 PLLA 共混膜在生理条件下结构发展、力学性能和水解降解的影响。在初始降解阶段，单向拉伸对质量损失没有影响；然而，在后期降解阶段，低拉伸比（DR）下，发育不良的晶体和无定形链可被降解，而在高 DR 下，不仅高度发育的晶体，而且取向的无定形链对水解变得不敏感。我们的工作提供了重要的分子水平结果，表明可生物降解材料可以具有优异的机械性能，并在生理条件下在所需时间内消失。
