Surface Modification And Biomimetic Mineralization Of Cellulose Biomass Template Scaffolds

The existing scaffolds for bone tissue engineering often have some shortcomings such as poor mechanical properties and insufficient bone imitation structure.In order to solve these problems,three kinds of phosphorylated cellulose/hydroxyapatite（HAp）composite scaffolds were prepared based on bottom-up and top-down approaches from the perspectives of pore size structure,functional modification,biomimetic mineralization and biocompatibility.The morphology,structure,mineralization effect and biocompatibility of the scaffolds before and after phosphoric acid modification were characterized and analyzed.In this paper,based on the bottom-up approach,sodium carboxymethyl cellulose/chitosan（CMC/CS）gel scaffolds with three-dimensional interconnected porous structures were prepared by electrostatic interaction and chemical cross-linking.The scaffolds with different pore structure,porosity and mechanical properties could be obtained by adjusting the proportion of the two substances.Subsequently,the phosphorylated scaffolds were obtained through sodium periodate oxidation and alendronate condensation reaction,and finally bionic mineralization was carried out in simulated body fluids.The phosphorylated composite scaffold CC-5-P-HAP can improve the mineralization ability,and HAp nanoparticles deposited on the surface are more regular and uniform.The Ca/P of CC-5-P-HAp is 1.34,which is closer to the composition of natural bone apatite.Cytotoxicity test showed that all the scaffolds were non-toxic and had good biocompatibility,which could promote cell proliferation and improve cell metabolic activity.The results show that the（bis）phosphonate-modified sodium carboxymethyl cellulose/chitosan/hydroxyapatite has a certain application potential in bone tissue engineering.In order to better simulate the layered porous structure of bone,the wood sponge and sugarcane stem sponge scaffolds were prepared based on the top-down approach after delignification with basa wood and sugarcane cellulose template.The two scaffolds retain the radial and longitudinal anisotropic porous tubular structure and mechanical properties of wood and sugarcane respectively,which can better simulate the natural bone structure and improve the porosity and cellulose accessibility.The porosity and mechanical properties of the scaffold could be adjusted by controlling the delignification time.Then the wood sponge was modified with esterified phosphoric acid,and the cane stem sponge was modified with ALN condensation phosphoric acid,so that anionic phosphate groups were introduced onto the surface of the scaffolds.Finally,the biomimetic mineralization was carried out in simulated body fluid to obtain the phosphorylated wood sponge/HAp composite scaffolds and the phosphorylated cane stem sponge/HAp composite scaffolds.The comparison of unmodified and modified composite scaffolds shows that the phosphate groups introduced by ALN modification and esterification modification improved the mineralization capacity of the scaffold.Phosphate groups provide more coordination sites for Ca²⁺complexation and promotes HAp nucleation and growth.The content of HAp deposited on the surface of phosphoric acid modified scaffold material is higher.The Ca/P of DW-5-P-HAP is 1.26,and the Ca/P of DS-4-P-HAP is 1.29.Meanwhile,the morphology,composition and crystallinity of DS-4-P-HAP scaffold material are closer to natural hydroxyapatite.Cytotoxicity tests showed that the two mineralized sponge scaffolds had good biocompatibility before and after phosphorylation.In conclusion,the phosphorylated wood sponge/HAp composite scaffolds and the phosphorylated cane stem sponge/HAp composite scaffolds are of great significance for improving the degree of bone imitating,mechanical properties and biological activity of scaffolds and preparing high performance bone repair scaffolds.