Biodegradable DL-PLA Foam Scaffold Material And Its Biological Evaluation

The development of modern medicine has made the dream true reconstructing or regenerating the damaged tissue and organs with artificial materials such as metal, polymer and ceram and so on. Despite their enormous distribution, these materials are foreign body. Permanent implanting material in body has problems about abrasion, property declining and security, et al. Temporary implanting material face several problems: if the mechanical property is matched with the replaced tissue or organs; if the degradation products are compatible and what is its metabolic pathway. The emergence of tissue engineering initiates a new method to regenerate damaged tissue or organs. At present, because of its good mechanical property and good biocompatibility, poly lactide (PLA) has become the most general material for extra cellular (ECM) of tissue engineering. And PLA was permitted to use in treatment as clinical material by FDA of USA.We want to synthesize Poly(D,L-lactic acid) and prepare porous foam scaffold with which.The ring-open polymerization of D,L-lactide was used in our experiment to synthesize poly(D,L-lactic acid). First we synthesize lactide from lactic acid, then yield the poly(D,L-lactic acid) by ring-open polymerization of D,L-lactide with the stannous octoate as the catalyst. The DL-LA and the DL-PLA were characterized by infrared spectroscopy (IR). And many factors in the reaction process were discussed.For example, temperature, dehydration time, dehydration content and the method of purification affect the purity and yield of lactide. The best reaction temperature is 240 ℃, and high vacuum and catalyst are beneficial. Reaction temperature, time, content of catalyst and vacuum level will affect the molecular weight of DL-PLA. The best reaction temperature is 160℃, the best reaction time is 4 hours, and the best catalyst content is 0.2%. At last, the catalyst Sn(Oct)2 is better than SnCl2 2H2O.We use solvent casting/particles leaching method to prepare three-dimension porous scaffold of tissue engineering. At first, the sodium chloride (NaCl) and PLA solution was mixed; secondly the solvent was volatilized, at this time, the NaCl existed in the polymer and took place some space. Then distilled water was used to exchange particles with NaCl to format pore. After the particles leaching, the porous foam scaffold was prepared. The scan electron microscope (SEM) was used to observe the surface pattern of the surface of the scaffold. The relation of content of particles and the porous of the scaffold was discussed. The porosity increased with the raising of the content of the particles, but have nothing with the size of the particles. And we think the pore size of scaffold is not only relation with particle's size, but also with the porogen content and its distribution state.Poly (D,L-lactic acid) was blended with Gly(Ome) in various mass fraction ratios by using solvent-mixing technique. The lactide, poly(D,L-lactic acid) and poly(D,L-lactic acid)/Gly(Ome) blends were characterized by infrared spectroscopy(IR). The result of the hemolysis experiments of DL-PLA and DL-PLA /Gly(Ome) blends showed the percentage of hemolysis of both the two material are less than 5%, which matches the standard of biomaterials. After doing the dynamic coagulation experiment, we draw the curve of the dynamic clotting time, which descended slowly, so we concluded the two material have little effect to coagulation time, even they have some anticoagulate effect. Pyrogen test of DL-PLA demonstrated that the pyrogen of the material meets a criterion.