The Study On M-MgO/PLLA Composites Crystallization And Degradation Properties In Vivo And In Vitro

Poly(L-lactide)(PLLA) has attracted wide attention due to its biodegradability and biocompatibility,and get the FDA certificate. There are two critical shortcomings that restrict its applications including severe inflammatory response and relatively poor mechanical properties, because of the molecular chain structure. The crystallization ability of PLLA is poor, and the initial degradation rate rapidly causes loss of mechanical properties.The researches show that inorganic nanoparticles as a kind of heterogeneous nucleating agent can effectively improve the crystallization ability of PLLA, at the same time, the polarity of nanoparticles can also increase the hydrophilicity of PLLA. Therefore, to improve PLLA crystallization, regulate the hydrolytic behavior and biological activity by the introduction of magnesium oxid has important research value.In this paper, we prepared magnesium oxide nanoparticles and whiskers with high aspect ratio by chemical method. The nanoparticles were modified with malic acid and oligo-polylactic copolymer, and the whiskers were surface modified with stearic acid. This study focuses on the effect of the magnesium oxide nanoparticles before and after modified on the poly(L-lacticacid) composites crystallization kinetics, mechanical properties and composite materials degradation properties in vivo and in vitro. Research indicates that:1. Only 0.5wt.% of magnesium oxide nanoparticles can effectively improve the crystallization properties of poly-L-lactic acid, heterogeneous nucleation of magnesium oxide nanoparticles significantly, greatly increased the rate of crystallization of poly-L-lactic acid material and the relative degree of crystallinity. The grain refinement, tensile strength and elongation at break showed multiple growth. Further increase in the concentration of nano particles of magnesium oxide on the crystallization process of poly lactic acid still has a promoting effect, but excessive concentrations against nanometer magnesia particles dispersed homogeneously, the improvement of the structure of poly lactic acid, and the relative crystallinity reduced accordingly.2. The good dispersion property of modified MgO nanoparticles makes the nucleation site of poly lactic acid significantly increased, and the crystallization rate of poly lactic acid was significantly promoted. Crystal particles uniformly refined, poly lactic acid spherulites growth is not perfect, the crystallinity decreased, but the mechanical properties were optimized, elongation at break and tensile strength improved significantly.3. Magnesium oxide additives can effectively control the degradation behavior in vivo and in vitro of PLLA, counteract acidity in the degradation intermediate of. Improve the hydrophilicity of PLLA, accelerate the initial degradation rate. But as the degradation of the extension of time, the magnesium oxide whisker can effectively inhibit the degradation of PLLA autocatalytic effect.4. MgO/PLLA composites had no toxicity to cells, and even had a little preliminary effect on cell proliferation. The addition of magnesium oxide whisker can improve the biocompatibility of the poly lactic acid, and promote the formation of the new bone.