Fabrication And Properties Of BMPLGA/NBG-?-TCP Composite Scaffold Materials

In the bone tissue repair engineering,the three-dimensional scaffold material composed of a single component is difficult to meet the requirements of the tissue engineering scaffold material;therefore,the construction of the composite scaffold material is an important direction of bone tissue engineering research.The biodegradable polymer scaffold material has a drawback of lacking of biologically active groups and accumulation of acidic substances in the degradation process,which affects its application in the medical field.Nano-bioactive glass?NBG?and?-calcium phosphate??-TCP?have high biological activity,biocompatibility,and certain cell and gene activation,but their brittleness is not conducive to the formation of materials.The combination of biodegradable polymer materials and inorganic ceramic materials is expected to provide three-dimensional porous scaffold materials with good biocompatibility,good osteoinductive effect,and excellent mechanical properties,breaking through the bottleneck that the natural tissue environment and mechanical strength cannot be taken into account,the research has important significance.In this work D,L-lactic acid and glycolic acid were used as raw materials.The crude lactide and glycolide were obtained by distillation under reduced pressure.The purity of both was purified by ethyl acetate and isopropyl alcohol,respectively.Maleic anhydride-modified poly?lactide-co-glycolide??MPLGA?was obtained by melt copolymerization.The results of infrared spectrum and nuclear magnetic characterization confirmed that maleic anhydride has been successfully introduced into the polymer chain.The results showed that the grafting rate was highest when the amount of maleic anhydride?MAH?was 9%?w/v?and the amount of benzoyl peroxide?BPO?was 0.28%?w/v?.By using N-acylation reaction,MPLGA was further modified with 1,4-butanediamine to obtain BMPLGA,and its hydrophilicity was significantly improved.Nano-bioactive glass?NBG?was prepared by sol-gel method using polyethylene glycol with a molecular weight of 20,000 as a dispersant and characterized by Fourier transform infrared?FT-IR?,X-ray diffraction?XRD?,transmission electron microscopy?TEM?and differential thermal weight?TG/DSC?.The results showed that the prepared NBG was amorphous and its particle size was between 50-100 nm.The nanoscale?-TCP was obtained by the solid-phase reaction method,using Ca?NO₃?₂·4H₂O water solution and?NH₃?₂HPO₄ aqueous solution in accordance with the precipitation reaction of Ca:P mole ratio of 1.5.FT-IR,XRD,TEM and TG/DSC were used for its further characterization.The results show that the particle size is between 100 and 200nm.BMPLGA/NBG-?-TCP composite scaffolds were prepared using room temperature moulding/particle stripping method using 150?m sodium carbonate?Na₂CO₃?as the porogen.The composite scaffolds were characterized by infrared spectroscopy.The effect of content of porogens on the morphology,porosity and compressive strength of the BMPLGA/NBG-?-TCP scaffolds were studied.The results showed that with the increase of the amount of the porogen,the micropores and the porosity of the composite scaffold material gradually increased;however,the compressive strength gradually decreased.Therefore,the porous structure,porosity and compressive strength of the porous scaffold can be controlled by controlling the percentage of the porogen.The BMPLGA/NBG-?-TCP composite scaffolds were soaked in PBS buffer.Changes in the pH,weight loss,water absorption,compressive strength,and morphology of the PBS solution during degradation of the scaffolds were investigated.The results showed that with the degradation of the scaffold material,the weight loss rate and the water absorption rate gradually increased,and the compressive strength of the material gradually decreased.The PBS solution pH rises first and then falls.From the scanning electron microscopy image,it can be seen that as the degradation progresses on the porous wall of the composite scaffold material material,micropores gradually increase.After 25 days,the micropores in the material can reach 50?m,but the scaffold does not collapse.The method of cell culture was used to study the cytotoxicity of BMPLGA by means of cell morphology observation and MTT colorimetry.The results showed that the introduction of maleic anhydride and 1,4-butanediamine was not cytotoxic,and MPLGA and BMPLGA had good biocompatibility.