Preparation Of Biodegradable Polymeric Porous Scaffolds And Their Biocompatibility Research

Biodegradable polymeric porous scaffold is one of the important research directions in the tissue engineering fields and plays a vital role in tissue engineering. Synthetic biodegradable polymers have well-controlled ability and have wide applications in tissue engineering. However, the poor hydrophilicity and lack of intergrin binding sites for cell attachment greatly limit cell growth on this kind of scaffolds. Hence, how to fabricate biodegradable porous scaffolds with good biocompatibility has become a hot topic in this field.The fibrous scaffolds fabricated by electrospinning could mimic the structure of extracellular matrix(ECM). Detailed investigation was conducted to improve the biocompatibility of the fibrous scaffolds. First, based on electrospinning, solution blending and freeze drying technique were combined to fabricate PPC/gelatin composite nanofibrous scaffolds, thermoplastic polyurethane(TPU)/graphene oxide(GO) small-diamter vascular scaffolds and the layered structured scaffolds with micro/nano fibers composed of PPC microfibers and chitosan nanofibers, respectively. There was severe phase separation between gelatin and PPC matrix at high loading of gelatin. Small amount of acetic acid was added into the electrospun solution to enhance the solubility of gelatin in the electrospu solution. The loaded acetic acid could improve the interaction between PPC and gelatin and make the electrospinning process of PPC/gelatin solution more easily. The added gelatin improved the hydrophilicy and cell biocompatibility of composite scaffolds greatly; TPU/GO small-diameter vascular scaffolds with different GO loading were prepared by home-made rotating collecting device. The effect of GO on the morphology, hydrophilicity and mechanical properties of TPU/GO was investigated in detail. 3T3 mouse fibroblast cell and human umbilical vein endothelial cells were used as cell models to investigate the loading content of GO on the cell growth, and it was found that lower content of GO was favorable for cell growth but higher content of GO result in cell death; Highly orientated PPC microfibrous scaffolds were prepared by adjusting the solvent composition and improving the collecting device. The chitosan nanofibers were introduced into the prepared PPC microfibrous scaffolds by freeze drying. The obtained scaffolds not only showed the micro/nano layered structure, but also contained the biocompatible chitosan on the surface, which enhanced the hydrophilicity and provide a suitable environment for cell growth.Secondly, the shish-kebab structured scaffolds were fabricated by combing electrospinning and induced polymer crystallization on the surface of the electrospun nanofibers to further mimic the microstructure of collagen fibrils in ECM not only on the structure but also on the function. The nanofibers were used as shish to induce the polymer molecules in the dilute solution to crystallize on the surface to form kebabs with periodic distance. The influence of compositions of shish and kebab solution on the morphology of shish-kebab structure was investigated, respectively. The shish-kebab structure prepared by using polycaprolactone(PCL)/nano-hydroxyapatite(n HA) composite nanofibers as shish had good biomimetic ability and were favorable for the MG63 cell growth. Compared with 77% aqueous acetic acid, PCL had lower solubility in pentyl acetate and the prepared kebab solution using pentyl acetate as solvent was good for the formation of regular kebabs. Chemically grafted matrigel onto the shish-kebab structured scaffolds could improve the hydrophilicity and biocompatibility of the scaffolds. Focused on the shortcomings of solution blending the chemical grafting, a new method to prepare the scaffolds was developed by decorating PCL nanofibers with chitosan-polycaprolactone copolymers. During the surface decoration, the PCL chains in the copolymers could spontaneously crystallize on the surface of PCL nanofibers and formed regular kebabs with periodic distance, while the chitosan backbones were exposed due to the repulsion of PCL nanofibers. The prepared fibrous scaffolds not only showed unique nanotopography endowed by shish-kebab structure, but also contained chitosan rich in cell binding sites. The prepared scaffolds developed by the proposed method showed good hydrophilicity, biomimic ability, cell biocompatibility and bone formation ability.As for electrospinning, the fabricated nanofibrous scaffolds lack integrity and it is difficult to produce three dimensional porous scaffolds using this method. While, the preparation process of thermally induced phase separation always involved toxic solvents. Therefore, a new technique was developed to combine the extrusion foaming, leaching and freeze drying to prepare the three dimensional bi-modal PCL porous scaffolds with chitosan nanofibers by optimizing the materials’ compositions and processing parameters. This technique could provide a new method to produce biocompatible, interconnected 3D porous scaffolds in scale-up.