3D Printing And Performance Study Of Chitosan-based Composite Scaffolds Based On Alkali/urea Dissolution System

Purpose:The preparation of bone biological scaffold is the key in bone tissue engineering.An ideal bone bioscaffold should have appropriate physical and chemical properties such as surface roughness,surface permeability,porous internal structure,suitable mechanical properties and degradability,as well as good biocompatibility,osteoinducibility and osteoconductivity.Magnesium ions can regulate bone metabolism and its immune microenvironment,promote angiogenesis,and facilitate the formation of vascularized bone tissue.Chitosan（CS）is a kind of natural cationic polysaccharide,which has good biocompatibility,degradability,coagulation and antibacterial effect.The discovery of alkali/urea dissolution system further optimized the properties of chitosan,such as excellent mechanical properties,uniform and stable structure,and gelation by simple temperature change.Hydroxyapatite（HA）is the main inorganic component of natural bone,which has good biocompatibility and bone conductivity,and has natural advantages in bone repair and regeneration.The purpose of this study is to dissolve CS by alkali/urea dissolution system,provide Magnesium oxide（MgO）with magnesium ion,add MgO and HA in CS solution to prepare biological ink,and use 3D printing technology to prepare a bone biological scaffold with good osteogenic activity and antibacterial propertyMethods:1.CS was dissolved by alkali/urea dissolution system,and MgO-HA/CS composite scaffolds with different MgO mass fractions（0%,0.25%,0.5%,0.75%and1%）were prepared by 3D printing and freeze-drying technology.2.Scanning electron microscope（SEM）and energy dispersive spectrometer（EDS）was used to observe the surface morphology and energy spectrum analysis of the composite scaffolds.The chemical groups and phases of the composite scaffolds were analyzed by Fourier transform infrared spectroscopy（FT-IR）and X-ray diffraction（XRD）.The physical and chemical properties of the scaffolds were characterized by porosity,water contact Angle,water absorption,compression performance,and degradability.The sustained release of Mgions was detected by Inductively coupled plasma spectroscopy（ICP）.3.The cytocompatibility of the scaffolds was evaluated by cell live/dead staining and CCK-8 assay.The osteogenic activity of the scaffolds was evaluated by alkaline phosphatase（ALP）staining.The plate colony counting method was used to detect the antibacterial property of the scaffolds.Results:1.MgO-HA/CS composite scaffolds with different mass fractions of MgO were successfully prepared.2.The surface of the composite scaffolds was rough,and the internal pores were connected to each other,with a porosity of about 64-69%,a pore diameter of 500-600μm,and a uniform distribution of magnesium ions.The chemical groups and crystal structures of MgO,CS and HA did not change significantly.The water contact Angle of the five groups of scaffolds was less than 30°,and the water absorption rate was155-168%.The composite scaffolds had good hydrophilicity.The elastic modulus was2.99-4.13 MPa,and the compressive strength was 0.30-0.39 MPa,which met the mechanical strength requirements of non-load-bearing bone.The degradation rate of scaffolds gradually increased with the addition of MgO,which could release Mg²⁺for a long time,and the concentration of Mg²⁺remained within the cell tolerance range.3.All the composite scaffolds had good biocompatibility,and the0.5MgO-HA/CS group had the most obvious cell proliferation and osteogenic activity.The antibacterial effect of the composite scaffold was enhanced with the increase of MgO content.Conclusion:In this study,MgO-HA/CS composite scaffolds with different MgO contents were successfully prepared by alkali/urea dissolution system,3D printing technology and freeze-drying technology.The physical and chemical properties,biocompatibility,osteogenic activity and antibacterial property of the five groups of scaffolds were comprehensively evaluated,and the scaffolds with 0.5MgO-HA/CS had the best comprehensive properties.It is a potential bone scaffold material.