Preparation And Characterization Of PDLLA/HA Scaffolds

As a result of axonal damage and the formation of scar tissue, cystic space, physical gap, functional deficits are induced by trauma to the nervous system injury. Autologous nerve grafting repair materials usually have the disadvantage of donor shortage. Therefore, bioengineering scaffolds should be undoubtedly the most ideally alternative materials for the nerve regeneration. Besides of good biocompatibility, none toxicity, scaffolds should also have good mechanical properties, pores direction, pores distribution and micro-structure, which may play an important impact on whether they are suitable for its bridging role and whether they can promote tissue repair and regeneration. In this research, a way to fabricate tubular scaffolds with membrane was found. The scaffolds have highly orientated pores from inside to outside, and uniform small pores. A solution casting method and a unidirectional temperature gradient combine with thermal-induced phase separation method were used to get porous structure. In order to promote cell attchment, proliferation, directional migration, orientated and stability of axon growth, as well as to achieve effective control of the degradation time of the scaffold, HA/PDLLA scaffolds were prepared and applied.In this dissertation, gelatin microspheres were prepared by micro-emulsion/ freeze-dried technique. Gelatin microspheres and salt particles were used as porogen. Homogeneous mixture of HA and PDLLA were poured into molds with porogen particles. Porous tubular scaffolds were then prepared by leaching out porogen particles. By a unidirectional temperature gradient and cooling temperature control, scaffolds were fabricated with suitable mechanical properties and uniform pores.The chemical structure of the scaffold was observed by Fourier Transform Infrared Spectroscope (FTIR). Results show that HA was excellently induced into the scaffold and the porogen particles have little effects on chemical structure. The morphology of the scaffold was observed by SEM. The results show that the porosity, pores size and pores shape can be effectively controlled by the porogen particles. The pores distribution and pore diameter can be controlled by using different molds and cooling method. It is indicated that the surface of scaffolds have uniform circular pores, and the pores distribute from inside to outside with an orientation. The mechanical properties of the scaffold were observed by Electron Universal Testing Machine. The compressive strength can reach to 0.55 MPa and compressive modulus is up to 6.81 MPa, which will basically meet the requirements of the mechanical properties in nerve repairment. The determination of mass loss rate changing with time was observed by vitro degradation. Degradation time was controlled by changing the porous of the film. And the effects of HA on the scaffolds degradation was evaluated by comparing different scaffolds. Considering the various factors which have an effect on the scaffolds, the most suitable scaffolds that meet the clinical demands were obtained.