Study On Mussel-inspired Adhesion/Calcium Phosphate Compoud And Its 3D Printing

Calcium phosphate cement（CPC）has become one of the commonly used bone repair materials due to its good biocompatibility and osteoconductivity.However,the insufficient mechanical strength of CPC limits its clinical application.In addition,traditional CPC bone repair scaffold preparation methods are difficult to construct complex structures and accurately match bone defects.Inspired by the"inorganic/organic"composite structure of natural bones,organic components are usually added to CPC to improve its mechanical properties.However,the low interaction between the organic component and CPC in an aqueous environment,and the low mechanical strength of the organic component itself hinder the improvement of the mechanical properties of the composite CPC scaffold.Inspired by the mussel adhesive protein,this study added a mussel-inspired adhesive（p（DMA-co-MEA）,p DM）into CPC to prepare a mussel-inspired adhesive/calcium phosphate-based bone cement composite CPC scaffold.The strong interaction of p DM with CPC in the water environment and its high strength improve the mechanical properties of the composite CPC scaffold.Secondly,develop p DM/CPC composite slurry suitable for extrusion 3D printing,and fabricate the 3D printed scaffold to meet the requirements of personalized customization;finally evaluate the cell compatibility of the composite CPC scaffold and the 3D printed scaffold.In this study,the composite CPC scaffold was prepared by introducing p DM into CPC by centrifugal drying method.The results showed that as the content of p DM increased,the compressive toughness of the composite CPC scaffold increased;when the mass ratio of p DM to CPC was 0.35:1（w/w）,the compressive strength of the composite CPC scaffold reached the maximum value of 29.71±3.5 MPa,approximately 5 times that of the control group（pure CPC scaffold）.The results of Fourier Infrared Spectroscopy（FTIR）,Raman Spectroscopy（Raman）,and X-ray Photoelectron Spectroscopy（XPS）indicate that there is a hydrogen bond and coordination cross-linking between CPC and p DM;scanning electron microscopy（SEM）observation shows that during the hydration process,the interaction between p DM and CPC particles gradually becomes tighter due to the enhanced interaction;¹H NMR and Raman results show that p DM itself will undergo coordination cross-linking and oxidative cross-linking during the hydration process;X-ray diffraction（XRD）showed that after steam pre-hydration and immersion hydration,the relative content of HA in the composite CPC scaffold was about 70%,and the presence of p DM inhibited the hydration reaction of CPC.The composite CPC powder was prepared by wrapping the p DM on the surface of CPC powder by blending and drying method,and the composite CPC powder was mixed with RO water to prepare a composite CPC slurry suitable for extrusion 3D printing.XPS and FTIR results show that hydrogen bonds are formed between p DM and CPC;as the content of p DM increases,the absolute value of the zeta potential of the powder increases,which is conducive to the dispersion of the powder;as the content of p DM increases,the optimal liquid-solid composite CPC slurry ratio lower,shorter curing time and improved molding performance are beneficial to 3D printing of composite CPC slurry.Raman and XRD data show that during the hydration process,p DM will produce coordination cross-linking between the surface of the CPC and the dissolved Ca²⁺;the presence of p DM inhibits the hydration of the CPC.The composite CPC scaffold and the 3D printed scaffold were co-cultured with bone marrow mesenchymal stem cells for 7 days in vitro.The results of Alamar Blue show that,compared to pure CPC scaffolds,composite CPC scaffolds are more conducive to promoting cell proliferation;there is no significant difference in cell proliferation between3D printed scaffolds and pure CPC scaffolds.A fluorescence microscope was used to photograph human umbilical vein endothelial cells（HUVEC）co-cultured with the composite CPC scaffold and the 3D printed scaffold for 3 days.The results showed that HUVEC can adhere to the composite CPC scaffold and the 3D printed scaffold and then spread.Alkaline phosphatase activity results show that compared with the pure cell group,the alkaline phosphatase activity of the 3D printed scaffold is stronger.However,as the content of p DM in the 3D printed scaffold increased,the alkaline phosphatase activity of the cells was inhibited.To sum up,this research introduces p DM into CPC.Due to the high viscosity of p DM in water and its high toughness,our experiment successfully prepare a composite CPC scaffold with both high toughness and high strength;on this basis,an excellent extrudability and formability 3D printed composite CPC slurry was fabricated;composite CPC scaffold and 3D printed scaffold have excellent cell compatibility.