| Background and ObjectiveCalcium sulfate hemihydrate(α-CSH)has good biocompatibility and osteoconductivity;however,it degrades quickly and lacks osteoinductive and antibacterial properties.The CMCS-Zn has the advantages of broad-spectrum antibacterial,promoting tissue repair and delaying degradation,and the compound also has the potential of zinc to promote bone formation.In this study,zinc carboxymethyl chitosan was compounded with α-CSH,in order to maintain the original characteristics of α-CSH,slow its degradation rate and make it osteoinductive and antibacterial;Novel composite biomaterial with moderate degradation rate,good biocompatibility,antibacterial,osteoinductive and osteoconductive properties.Method1.Preparation,physical and chemical detection and degradation experiments of composite materials.CMCS-Zn and α-CSH were formulated into composite materials with different mass ratios and mixed with deionized water to form a paste to test the setting time and injectability.Then,the composite material paste was made into a certain size bone cement cylinder using a mold.Compressive experiments,X-ray diffraction analysis(XRD),Fourier infrared spectroscopy(FTIR),electron microscope scanning(SEM)to check the strength,structure and characterization of materials,simulated degradation experiments to analyze the degradation performance of materials and measure the pH of the degradation value and Ca2+,Zn2+ion concentration.2.In vitro cell experiments and bacterial experiments to detect biological properties of composite materials.The extracts of experimental materials were prepared to interfere with the growth of BMSCs.CCK-8 detection and scratch healing experiments were used to analyze the proliferation and migration activity of BMSCs cells after intervention;qRT-PCR was used to detect cell alkaline phosphatase/Runx2/osteocalcin/osteosialin gene expression levels;Von Kossa staining experiment Detection of mineralization.The sterile filter paper soaked with the extract of the experimental material was cultured in S.aureus and E.coli plates,respectively,and the antibacterial performance of the material was tested.3.Animal experiments to test the osteogenic effect of composite materials in vivo.A critical animal bone defect model was established and experimental materials were implanted.Use X-ray,Micro CT,and histomorphology to evaluate the overall effect of materials on bone formation.Results1.With the increase of CMCS-Zn content,the solidification time and injectability of composite materials also increased and were higher than α-CSH;compressive strength decreased with the increase of CMCS-Zn content and were lower than α-CSH;XRD and FTIR inspections showed that no new phase was formed after mixing CMCS-Zn with α-CSH in the novel material;SEM scans revealed that the pore structure of the new material before and after degradation was increased compared to α-CSH;the degradation rate of the novel material was slower thanα-CSH,which decreased with the increase of CMCS-Zn;during the degradation of the novel material,the pH was relatively stable and maintained at 6.0-6.2;the release trend of Ca2+was not significantly different from α-CSH,and the release of Zn2+increased with the increase of CMCS-Zn content.2.Detection of cell proliferation by CCK-8 indicated that the cells in each group proliferated well.qRT-PCR showed that the extracts from each group of composite materials could up-regulate cell alkaline phosphatase/Runx2/osteocalcin/osteosialin gene expression levels;the scratch healing rate of the composite material group was better than α-CSH,the 5%group is particularly obvious.The number of mineralized nodules in the composite material group was significantly higher than α-CSH group.The antibacterial ability of the composite material increased with the increase of CMCS-Zn.3.X-ray and Micro CT results revealed good bone defect healing in the novel material group;analysis of the number,volume,and density of new bone trabeculae 4 and 8 weeks after material implantation:5%CMCS-Zn/α-CSH group>10%group>15%group>CSH group.Histomorphological examination shows that the novel material group was more osteogenic.Conclusion1.The novel material has a moderate coagulation time and good injectability;its compressive strength was equivalent to normal cancellous bone;it had a good pore structure;its degradation rate was slower than α-CSH and the release of calcium and zinc ions during the degradation process can promote bone formation.2.The novel material had good biocompatibility and can significantly increase the proliferation and migration activity of BMSCs;it also up-regulated the expression of osteogenic genes and had osteoinductive properties;and it also had strong resistance to Staphylococcus aureus and E.coli.3.The novel material can promote bone repair in bone defect areas more thanα-CSH.The in vivo degradation rate of novel materials was more compatible with bone repair.Among them,5%CMCS-Zn/α-CSH has the most overall repair effect. |
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