Structure And Performance Optimization Of Porous Scaffolds Composited Highly Dispersed Nano-Hydroxyapatite With Polylactic Acid

With the increasing global aging,osteoporosis in middle and old age has become one of the important global health science issues.The development of an artificial bone repair scaffold that can induce self-repair and promote bone regeneration in the human body in a clinical setting is crucial for the repair of osteoporotic bone defects.As a completely biodegradable and environmentally friendly material,polylactic acid（PLA）is widely used in the field of bone tissue engineering for its good biocompatibility,ease of processing and molding,and good mechanical properties.Hydroxyapatite（HA）is a major inorganic component of human and animal bones,and its compounding with PLA confers osteoinductive and osteoconductive properties to PLA.And strontium（Sr）element has the function of promoting osteogenesis and inhibiting bone resorption,which can impart good biological properties to HA by functional ion doping.In this study,a variety of modifiers were used to modify the surface of HA nanoparticles to improve their dispersibility.The HA/PLA porous composite scaffolds were prepared using a combined solution blending-vacuum drying method,and the microporous structure of the porous scaffolds was tuned by controlling the experimental conditions.Analytical test methods such as X-ray diffraction,Fourier transform infrared spectroscopy,field emission scanning electron microscopy,and universal testing machine were used to focus on the physical phase composition,microscopic morphology,compressive strength,and thermal stability of HA/PLA porous composite scaffolds.In addition,the in vitro degradation properties of the porous composite scaffolds with Sr ion-doped HA were investigated and their biological properties were characterized.It was shown that the surface modification of HA by four substances,KH-560,S A,C16TAB and PEG,all alleviated the agglomeration phenomenon of HA to different degrees.Among them,PEG-HA showed comprehensive comparative advantages,with the modified HA particles having larger zeta potential at pH 7,smaller agglomerate particle size in water,and the longest complete settling time in 1,4-dioxane organic solvent.The compressive strength of the prepared porous composite scaffold materials showed a trend of increasing and then decreasing with the increase of HA mass fraction.The compressive strength peaked when the HA addition mass fraction was 10%.After changing the pre-freezing temperature to optimize the structure of the porous scaffold,the pore size of the scaffold became smaller and smaller as the pre-freezing temperature decreased,which made the overall density of the scaffold become larger,so that the compressive strength it could withstand also became larger.Under the same prefreezing temperature,the compressive strength of the bracket still shows a trend of increasing and then decreasing with the increase of HA mass fraction.The pore size of the scaffolds prepared at the pre-freezing temperature of-196℃ was 5-10 μm,and the compressive strength of the 10wt%-PEG-HA/PLA scaffolds reached 2.03 MPa,which was the highest value among the tested materials.In addition,the surface contact angles of the composites all gradually decreased with the increase of HA content,and the effect of surface modification substances was not obvious.Overall,Sr²⁺doping improved the in vitro degradation weight loss rate of the scaffolds.During in vitro degradation,Sr-PEG-HA/PLA composite scaffolds slowly released Sr²⁺and did not cause a significant change in buffer pH.In vitro cell culture assays showed that the prepared composite scaffold materials were non-cytotoxic,with 7%-Sr-PEG-HA/PLA exhibiting the most pronounced promotion of mBMSCs cell proliferation.