Study On The Process And Performance Of Selective Laser Sintered Hydroxyapatite/Polylactic Acid Composite Material

Bone and joint system disease is the most common cause of disability,incapacity to work and poor quality of life,and their treatment often requires the use of implants.Biodegradable biomaterials have gradually become a research hotspot in bone tissue engineering due to their advantages such as better matching of modulus with human bone,and without need for secondary surgery.Polylactic acid(PLA)has been widely used in biomedicine due to its good biodegradability and biocompatibility,but its degradation products show local acidity which is the main reason to limit its use as an implant alone.Hydroxyapatite(HA)is one of the main inorganic components of human bone matrix,which not only has good biocompatibility and bone inductivity,but also its hydrolytic products can neutralize the local acidity of PLA.Therefore,HA/PLA composite materials are widely used as suitable implant systems.However,the traditional HA/PLA composite process methods,such as injection molding and compression molding,are unable to process the complex structure,and various problems such as residual organic solvents are accompanied during processing.Selective Laser Sintering(SLS)technology is a kind of powder bed melting additive manufacturing technology,which stands out in many implant processing methods because of the advantages of personalized preparation of complex parts.Therefore,this paper systematically studies the SLS preparation process of HA/PLA composite materials,which is suitable for the preparation of bone plate and other related parts.Taking into account the reasons for the slow degradation of PLA in vivo and the cause of inflammation,the SLS process of nano-HA/PDLLA(nano-Hydroxyapatite/Poly(D,L-lactic acid))composites was studied to obtain high-performance drug-loaded precursor scaffolds and other related parts.The specific research contents and results are as follows:(1)The particle size of composites prepared by ball milling and S/O/W(Solid-Oil-Water)processes are suitable for SLS process.The results of the process optimization experiments of pure PLA show that the optimal laser energy density range is 0.040?0.075 J/mm~2,within which the tensile strength is greater than 23 MPa and the maximum is up to 27 MPa.XRD results show that during SLS processing,the?crystal shape of PLA changed to?'crystal shape,and with the increase of energy density,the surface columnar crystals will increase and grew.The results of tensile and bending properties show that 10wt%HA is the optimal doping ratio,and the tensile strength and microstructure of the composite were the highest.(2)The water contact angle test results show that the addition of HA can improve the hydrophilic properties of PLA.Vickers hardness results show that HA can increase the overall hardness of HA/PLA composites.Biological performance experiments indicate that the composite has good cell adhesion,and the hydrolysis of the added HA may cause local acid-base imbalance and cytotoxicity.The comparative analysis of mechanical properties of SLS parts and injection parts shows that the tensile strength of SLS parts can reach more than 80%and the bending strength can reach more than 55%of the injection parts,which can meet the strength requirements of bone plate materials.(3)By optimizing the SLS process of nano-HA/PDLLA composite microspheres,the optimal laser energy density range is 0.020?0.030 J/mm~2.The tensile property results show that as the content of nano-HA content from 0wt%to 10wt%,the tensile strength decreases from 1.714 MPa to 1.295 MPa,and the tensile modulus decreases from 7.198 MPa to 6.514MPa.Nano-indentation test results show that nano-HA improves the overall hardness of the samples,thereby ensuring the structural stability before and after drug loading.The dynamic contact angle test shows that after adding nano-HA,the hydrophilic property of the material is improved,which is beneficial to the exchange and transportation of nutrients in the body.(4)Cell adhesion and toxicity tests show that the cell proliferation rate of SLS samples is relatively high,indicating that the SLS process is non-toxic and harmless.The results of degradation experiments show that degradation occurs as a whole,and nano-HA can regulate the degradation rate of composite materials.Physical,chemical,and biological test results indicate that the inherent characteristics of the samples after SLS processing have not changed.Therefore,the current work proves that using this method to form drug-loaded microspheres is feasible,which provides a theoretical basis for the feasibility of this material as a drug-loaded precursor material.Therefore,the current work proves that it is feasible to process nano-HA/PDLLA composite using SLS,which provides a theoretical basis for the feasibility of this material as a drug-loaded precursor material.