Research On The Preparation And Cell Compatibility Of Bioactive Glass Scaffolds For Tissue Engineering

To develop a new type of bone tissue repair material to help the patients repair the defector missing bone tissue and restoration of human hard tissue, the medical academia and thebiomedical materials academia have been trying to solve this problem over the years. In thisstudy, first, the bioactive glasses with curled lamellar structure were prepared by sol-gelmethods, and then the bioactive glass-ceramic scaffolds were produced by in-situsolidification molding process with rapid prototyping techniques. As a result, the bioactiveglass-ceramic scaffolds with regular pore structure have a high mechanical strength andcertain porosity; we also studied the preparation process, the physical and chemical properties,the apatite biomineralization activity and the cytocompatibility between the scaffold andMG-63osteoblasts. The main results as follows:First, the45S5bioactive glass were prepared by conventional melting method, the58Sbioactive glass powders with curled lamellar structure were prepared by sol-gel technologyusing non-ionic block copolymer P123as the template. After immersion in SBF, we foundthat HCA crystals gradually nucleation and growth on the surface，finally covered the wholesurface with the immersion time increased. This indicated that the45S5and58S bioactiveglass have a good bioactivity and in vitro biomineralization.Second, to improve its fluidity and stability, a certain dispersing agent were added into the45S5bioactive glass slurry, then the bioactive glass-ceramic scaffolds were prepared byin-situ solidification molding process with a high mechanical strength and certain porosity,partially crystallized with Na₄Ca₄(Si₆O₁₈) crystals. The μCT results showed that the porosityis about61%which meet to the basic requirements of cancellous bone porosity; thecompressive strength of the scaffold is12.37±1.25MPa also meet to the mechanical strengthof cancellous bone requirements.Third, to test its bioactivity and biomineralization, the bioactive glass scaffolds weresoaked into SBF and observed apatite generated. The results showed that the HCA crystalnucleation and growth on the surface of the scaffold gradually with the immersion time increased, and covered with the whole surface after immersion for14days, it indicated thatthe scaffold had a good biomineralization. The pH value of the SBF were recordedsimultaneously after immersion, it presented a fast-growing trend at first day, then growthslowed, three days later, it reached a relatively stable state at around7.65. The weight loss ofthe scaffold after immersion was tested; it underwent an immediate loss of8-9%during thefirst day, and held this value until7days, then decreased to20.7%on21days. A dynamicequilibrium appeared and thus the scaffold weight was stabilized during1-7days immersion,the reason maybe the scaffold dissolution consistent to the formation of HCA. The ionconcentration of the SBF after the scaffold immersion was also tested; Si ion concentrationshowed a rapid increase and continued to increase slowly after24h of immersion, Si ionrelease mainly controlled by diffusion at early age and slowing down for the formation of theHCA mineralization layer. Ca²⁺ion concentration tends to a stable value after immersion for24h; this maybe due to the formation of apatite and ion dissolution reached a dynamicequilibrium. The concentration of P was gradually decreased with the time increased, thatbecause P was an essential element to generate apatite but it was dissolved from the scaffoldinsufficiently. Finally, we studied the kinetics of Si ion release, found that the release of Si in0-24h period followed to the release of first-order kinetics model and belonged todiffusion-dissolved control process. This Si release process is started due to the scaffold, theSi concentration in solution is almost0at this time, according to the diffusion releasemechanism, the release rate of Si is rapidly at the initial stage, and then tend to be gentlerelease stage.Finally，the effect on cell adhesion and proliferation were discussed between the regularand irregular pore structure using MG-63cells as a model. After one day co-culture, MG-63cells have been found in a large number of pseudopodia and adhered to the scaffold surface bySEM. MTT methods were used to test the proliferation of the cells on the bioactive glassceramic scaffold, and found that the regular porous structure was significantly higher cellactivity than the irregular porous structure, and the difference between two groups isstatistically significant.