Preparation And Properties Of PLLGC/NBAG-β-TCP Porous Scaffold Material

The bone tissue engineering composite scaffold can combine the characteristics of various materials to make up for the lack of performance of each other.Its construction is one of the research hotspots in the field of bone tissue engineering.Aliphatic alpha hydroxy acid biomedical degradable polymers have good biocompatibility,but their application range is limited due to the lack of bioactive groups and the accumulation of acidic degrading substances.Nanobioactive glass(NBAG)andβ-calcium phosphate(β-TCP)have high bioactivity,osseointegration strength and osteogenic induction ability,but their brittleness is too large to facilitate processing.Based on the research status at home and abroad,this paper intends to combineα-hydroxy acid polymer with NBAG andβ-TCP to obtain a new bone tissue engineering scaffold material with good biocompatibility,strong osteogenic induction and excellent mechanical properties.L-lactic acid and glycolic acid were used as raw materials to prepare L-lactide and glycolide by vacuum distillation.The two monomers were then purified and mixed withε-caprolactone to prepare PLLGC by melt polymerization using stannous octoate as a catalyst.The products were analyzed by infrared spectroscopy and nuclear magnetic resonance spectroscopy.The results show that the L-lactide and glycolide have relatively high purity,and the weight average molecular weight of the ternary copolymer PLLGC obtained by polymerization reached 1.2×10~5 Da.Nano-bioglass was prepared by sol-gel method combined with freeze-drying.Nano-scaleβ-calcium phosphate was prepared by solid-phase reaction precipitation method,and modified by aminopropyltriethoxysilane.The corresponding products were analyzed by FTIR,XRD,TG-DSC,SEM and EDS.The results show that the prepared NBAG is amorphous andβ-TCP has a good degree of crystallization.The size of the two nanoparticles is between 100 and 200 nm,and the N element is successfully introduced on the surface.The PLLGC porous scaffolds were prepared by thermal phase separation method.The morphology of the PLLGC was observed by SEM.The effects of PLLGC concentration and freezing temperature on the morphology and pore structure of the porous scaffolds were studied.It was found that porous scaffolds have good morphology and suitable pore size with the concentration of PLLGC is 10wt%and the freezing temperature is-30°C.The effects of polymer concentration and freezing temperature on its porosity and compressive strength show that the higher the polymer concentration,the lower the porosity of the scaffold material and the higher the compressive strength.The lower the freezing temperature,the lower the porosity of the scaffold material and the greater the compressive strength.The PLLGC/NBAG-β-TCP composite scaffold material was prepared by solution blending-freeze drying method.The scaffolds were observed by SEM.The results show that the prepared scaffolds have interpenetrating pore structures,NBAG andβ-TCP are evenly distributed on the pore walls.The effects of inorganic content and freezing temperature on the porosity and compressive strength of composite scaffolds were studied.The results show that as the inorganic content increases,the porosity of composite scaffolds decreases,and the compressive strength increases first and then decreases.When the inorganic content is 10 wt%,the compressive strength reaches the maximum;The effect of freezing temperature on the porosity and compressive strength of composite scaffolds is consistent with that of PLLGC scaffolds.The degradation of PLLGC porous scaffold and PLLGC/NBAG-β-TCP composite scaffold in PBS buffer was investigated.The results showed that during the degradation process,both scaffold materials decreased the pH value of PBS buffer,and their weight loss rate and water absorption rate increased gradually,but the weight loss rate and water absorption of PLLGC/NBAG-β-TCP composite scaffold materials are always higher than that of the PLLGC scaffold material.In addition,the compressive strength of the two scaffold materials is gradually decreased,but the composite scaffold material always maintains a higher compressive strength;after one month of degradation,the pore structure of the two scaffold materials is more pronounced than before the degradation,and the pores are more loose.In vitro cell biology experiments were performed on PLLGC scaffolds and PLLGC/NB-AG-β-TCP composite scaffolds using adipose stem cells.The morphology of the cells inoculated on the scaffold was investigated by SEM.The cell adhesion and proliferation were qualitatively examined by confocal fluorescence microscopy.The cell proliferation was observed by CCK-8 method and the cell proliferation curve was obtained.The results showed that the inoculated cells increased with the increase of culture time,and the two scaffold materials had good biocompatibility,but the PLLGC/NBAG-β-TCP composite scaffold had better biocompatibility.