Structural Design And Biological Applicability Of PLA Porous Scaffolds

Tissue engineering porous scaffolds simulate the structure of extracellular matrix,and replace the function of tissue in specific damaged tissues to provide a temporary growth environment for cells and new tissues.In the process of tissue engineering,the material’s design and three-dimensional structure’s construction of tissue engineering scaffolds have always been the focus and difficulty of various researches.Polylactic acid is one of the most widely used green macromolecules for the preparation of biological scaffolds.It has good biocompatibility and degradability.It is degraded into carbon dioxide and water in the body and is non-toxic and harmless to human body.In this paper,polylactic acid(PLA)porous materials with multilevel structure were prepared by phase separation and template spinning,aiming at the problems of low porosity,poor cell adhesion and penetration growth.In order to meet the antibacterial requirements of tracheal stent materials,novel molecular structures such as graphene and ionic liquid were designed to achieve the synergistic antibacterial function of porous materials.The specific research content of this paper is as follows:(1)The open-porous scaffolds were prepared by non-solvent phase separation with stereocomplex polylactic acid(sc-PLA)/polyadipic acid/butyl terephthalate(PBAT)as matrix,investigated the effects on the porous structure and performance of the scaffolds by the stereotactic effect,water-oil ratio and the content of PBAT.The results show that the stereotactic effect of PLA is beneficial to the formation of more regular porous structure;The higher the value of water-oil ratio,the larger the pore diameter and the higher the porosity of the prepared scaffolds;However,when the water-oil ratio is higher than 0.8:1,demulsification will occur and the pore wall of the material will fracture.Therefore,when the water-oil ratio is 0.7:1-0.8:1,the material has a high porosity and the pore structure is the most complete;At the same time,with the increase of PBAT content,the pore diameter and porosity of the material decrease at the same time,and the fracture elongation increases.(2)Using copper mesh with different structures to replace the traditional spinning image screen,multilevel structure electrospinning tissue engineering membranes based on sc-PLA and natural collagen were prepared.The formation mechanism of multilevel structure,the effect of the introduction of collagen and stereotactic effect on scaffold structure and biological properties were discussed.The study shows that:The introduction of multilevel structure can improve the elongation and fracture strength at the same time;The introduction of collagen greatly improved the hydrophilicity of spinning materials;In the process of cell culture in vitro,it was found that fibroblasts can only grow on the surface of random fibrous membranes,but can achieve penetration growth in multi-structure spinning.The composite tissue-engineered trachea scaffold was prepared by combining the electrospinning membranes with the 3D-printed skeleton of polylactic acid and transplanted into rabbits.The conclusion was obtained that multilevel structure electrospinning membranes can promote tissue growth.(3)As a nanocomposite for modifying L-poly(lactic acid),GO-g-PLLA was synthesized by ring-opening polymerization of lactide.Studies have shown that when the content of nanoparticles is less than 2%,the crystallinity of the material system increases with the increase of GO or GO-g-PLLA,indicating that they can be used as heterogeneous nucleating agents of PLLA;With L-lactic acid as the matrix and GO-g-PLLA as the nanofiller material,a multilevel structure electrospinning membranes with controllable morphology was prepared by template electrospinning method,and it was found that fibroblasts could achieve penetration on it;The antibacterial effect of fibrous membranes were evaluated by two methods of antibacterial quantification and morphological observation.The results showed that PLLA/GO and PLLA/GO-g-PLLA fibrous membranes had significant antibacterial activity against escherichia coli and staphylococcus aureus.(4)Imidazole ionic liquids are synthesized by substitution reaction,and ionic liquid functionalized graphene oxide nanoparticles(GO-g-IL)were synthesized by condensation reaction.With sc-PLA as the matrix and GO or GO-g-IL as the nanofillers,three different multilevel structure electrospinning membranes were prepared by template electrospinning method.The antibacterial electrospinning membranes were combined with the 3D-printed TPU skeleton to prepare the composite tracheal scaffolds.Studies have shown that sc-PLA has almost no antibacterial ability,while sc-PLA/GO has certain antibacterial ability,sc-PLA/GO-g-PLLA electrospinning membranes has the best antibacterial effect and achieves the synergistic antibacterial effect.