Preparation And Properties Of Hydroxyapatite And Polylactic Acid Composites

Nano-hydroxyapatite(nHA)has a large surface energy and is unevenly dispersed in polylactic acid(PLA),which leads to agglomeration and affects the comprehensive properties of hydroxyapatite/polylactic acid(HA/PLA)composites.Therefore,different kinds of hydrophilic modifiers were selected to surface-modify nHA to improve the dispersibility of nHA in HA/PLA composites.By analyzing the modification effect of hydrophilic modifiers such as dopamine(DA),polyethylene glycol(PEG)and chitosan(CS),the DA with good bioactivity and oxidizable self-polymerization was selected as Hydrophilic modifier of HA.Infrared analysis of modified HA revealed the characteristic functional groups of polydopamine(PDA).Simultaneously,the particle size of the modified HA increased significantly,indicating that the hydrophilic modifier DA oxidized and self-polymerized to form PDA to achieve the coating modification of HA.When the amount of DA is 6 wt%,good dispersion of HA in PLA can be achieved.HA/PLA composites should have a high porosity when used in the field of bone tissue engineering.Therefore,it is necessary to prepare a HA/PLA porous composites by a pore-forming method.In this experiment,anhydrous ethanol was used as a porogen to prepare a porous composites.Since HA has a high solubility in anhydrous ethanol,and simultaneously,anhydrous ethanol is a poor solvent for PLA,phase separation can be induced to achieve pore formation of the composites and good dispersion of HA in the matrix.Anhydrous ethanol has the characteristics of fast evaporation,high efficiency and non-toxicity.The obtained porous composites has good pore structure morphology and the porosity is up to 49.91%,but the ratio of HA to PLA is not more than 4:10.Porous composites need to meet the performance requirements of bone tissue engineering for composites,especially mechanical properties.Therefore,porous composites need to be reinforced.Degummed silk fiber(DSF)was selected as the reinforcing material.Simultaneously,DA modified DSF reduced silver ions to generate nano silver particles(Ag NPs)in situ,and imparted antibacterial activity toDSF to obtain antibacterial degummed silk fiber(ADSF).Modified nHA as a filler,ethanol as a porogen,and ADSF as a reinforcing material to prepare ADSF/nHA/PLA porous composites.The ADSF/nHA/PLA porous composites has good pore structure and porosity up to 75.8%,which is beneficial to cell adhesion,proliferation and differentiation.ADSF has a good interfacial interaction with the matrix,and the compressive strength is up to 9.9 MPa.Simultaneously,with the increase of the content of nHA,the mineralized crystal layer on the surface of ADSF/nHA/PLA porous composites is more perfect,and the osteogenesis ability of the composites is improved.The introduction of ADSF had no significant effect on the proliferation of MC3T3-E1 cells,while the OD value of the bacterial solution containing the porous composites was significantly reduced,showing good antibacterial activity.