Antibacterial Modification Of Hydroxyapatite By Gadolinium And Its Composite Bone Tissue Engineering Materials

With the aging of the global population and the frequent occurrence of accidents,orthopedic diseases have become very common diseases,making bone tissue engineering materials become one of the most in clinical demand.Clinically,bone tissue engineering materials often bring about postoperative infection and rejection problems.Therefore,the ideal bone tissue engineering materials should possess certain antibacterial properties and biological activity.In this paper,the antibacterial properties of 14 rare earth oxides were compared through their antibacterial rates.Gadolinium（Gd）,a rare earth element with good antibacterial properties against both Gram-negative bacteria Escherichia coli（E.coil）and gram-positive bacteria Staphylococcus epidermoides（S.epi）was selected as the antibacterial phase.In order to prepare bioactive bone tissue engineering materials,hydroxyapatite（HA）prepared by chemical synthesis method was used as the bio-phase.According to the properties that Ca²⁺can be replaced by Gd³⁺in HA lattice,Gd³⁺was added to HA lattice for its antibacterial modification during the chemical synthesis process.According to the atomic ratio Gd³⁺/(Ca²⁺+Gd³⁺),the doping ratio of Gd=0.05,0.075,0.1,samples were written as Gd_x-HA（X=0.05,0.075,0.1）.XRD,TEM and XPS tests proved that Gd was successfully incorporated into HA lattice and formed Gd-HA interstitial solid solution.After the preparation of Gd-HA sample,as bone tissue engineering it was studied in this paper.First,Gd-HA biological coatings were prepared on the surface of Ti substrate by liquid flame spraying.In the study of Gd-HA biological coatings,XRD test showed that the high temperature process of flame spraying caused a certain degree of decomposition and lattice change of Gd-HA.SEM and 3D profile observed the surface morphology of the coatings.Microhardness test showed the coatings possess good mechanical properties.The antibacterial and bacterial adhesion experiments of Gd-HA coatings on E.Coil and Staphylococcus proved the material possess good antibacterial properties.The proliferation test of osteoblasts indicated the coatings have good biocompatibility and are conducive to the growth and proliferation of cells.Moreover,the antibacterial and cell proliferation promotion ability of the coatings were improved with the increase content of Gd.The other used form was to prepare three-dimensional bone filler Agarose/Gd-HA by compounding Agarose（AG）.SEM test showed the Agarose/Gd-HA have porous and complete three-dimensional structure.The expansion rate and water retention tests showed the addition of Gd-HA reduced the expansion rate of biomolecular AG and improved its water retention.Mechanical properties testing（compressive strength,compressive stress,elastic modulus）showed the fillers possess certain mechanical properties that can meet certain biological applications.In the evaluation of antibacterial performance and biological activity of the fillers,it was found Agarose/Gd-HA material possess well antibacterial performance in antibacterial and bacterial adhesion experiments on E.Coil and Staphylococcus.CCK-8 test and cell adhesion characterization of osteoblasts indicated the fillers possess biocompatibility and was conducive to the growth and proliferation of cells.Alizarin red staining experiment of osteoblasts proved the fillers can promote the differentiation of osteoblasts.The antibacterial performance and biological activity of Agarose/Gd-HA fillers enhanced with the increase content of Gd in the range of 5%-10%.The research work of this paper mainly explored the antibacterial properties of rare earth elements and successfully prepared Gd-HA materials with both antibacterial properties and biological activities.Based on this,Gd-HA as biological coatings on the surface of implant material and Agarose/Gd-HA as 3D bone fillers were studied.The results revealed Gd-HA materials possess good antibacterial performance and biological activity,and are promising bone tissue engineering materials.Above studies also provide feasible basis and ideas for the exploration of new antibacterial agents,modification and development of bone tissue engineering materials.