Preparation Of Micro/nanostructure HA/PDA/CMCS Bifunctional Composite Scaffold And Its Anti-tumor And Pro-osteogenic Differentiation Properties

Bifunctional bone repair materials with good photothermal effect and excellent osteogenic properties are of great significance for clinical treatment of bone tumors.In this study,the micro-nanostructure hydroxyapatite(HA)was firstly prepared in batches by hydrothermal synthesis.By exploring different hydrothermal conditions,the optimal condition for preparing hydroxyapatite particles with uniform morphology was screened.The micro-nanostructure hydroxyapatite particles were surface-modified with polydopamine(PDA),and then combined with carboxymethyl chitosan(CMCS)as the 3D printing paste;finally,the micro-nanostructure HA/PDA/CMCS bifunctional composite scaffold was fabricated by 3D printing technology.In addition,the therapeutic effect of the composite scaffold in vitro and in vivo on photothermal anti-tumor therapy and the osteogenic differentiation of mouse bone marrow mesenchymal stem cells in vitro were evaluated.The main findings are as follows:The sodium citrate(Ct)was used as a template to prepare micro-nanostructure hydroxyapatite by hydrothermal synthesis.The results show that the calcium ion concentration significantly affects the self-assembly of hydroxyapatite nanocrystals and leads to different morphology of hydroxyapatite particles,including spherical,dumbbell-shaped and two-dimensional plate shape;changing the Ca/Ct molar ratio has less effect on the morphology and polydispersity coefficient of the particles.However,the particle size decreases as the Ca/Ct molar ratio increases.Calcination treatment at 800~1000°C causes the surface of hydroxyapatite to fuse and destroys its original surface micro-nanostructure.The final preferred batch preparation of the HA particles having uniform size and micro-nanostructure is as follows:a calcium ion concentration of 0.2 mol/L,a Ca/Ct molar ratio of 2/5,and no calcination.The orthogonal formula and rheological property characterization were used to explore the most suitable slurry composition formula for 3D printing,and the effects of different distribution ratios and crosslinking time on the mechanical properties of the stents were explored.The results show that dopamine can effectively improve the rheological properties of the slurry and significantly improve the mechanical properties of the scaffolds.The composite scaffolds were irradiated with 808 nm near-infrared laser to explore their photothermal effect.The results show that the dopamine content and laser power density in the scaffold could effectively regulate the photothermal temperature of the scaffold;at a power density of 0.45 W/cm~2,the dopamine-modified composite scaffolds exhibited excellent photothermal effects,while the unmodified composite scaffolds had no photothermal effect.The excellent photothermal properties of the dopamine-modified composite scaffolds can effectively kill tumor cells in vitro and can effectively inhibit the growth of subcutaneous tumors in nude mice.At the same time,the dopamine-modified composite scaffolds can enhance the expression of osteogenic related genes,promote the osteogenic differentiation of mouse bone marrow mesenchymal stem cells,and have good osteogenic properties.In conclusion,the high specific surface area and biological activity of the micro-nanostructure HA can confer high-efficiency stem cell osteogenic differentiation performance on the composite scaffold;the higher near-infrared photothermal conversion efficiency of dopamine gives the composite scaffold a highly efficient photothermal ablation tumor function.