Fabrication And Characterization Of Zn-based Porous Scaffolds For Bone Tissue Engineering Application And Its Surface Modification

Recently,zinc and its alloys are attracting intens ive interest as promising biodegradable biomaterials.Their moderate degradation rate makes them a better potential candidate for porous scaffolds than Mg-based alloys.In present study,hot pressing sintering(HPS)was innovatively adopted to manufacture Na Cl templates with high compacting dens ity.And then,open porous pure Zn and Zn-3wt.%Cu scaffolds were achieved by infiltration casting process.The pore structure,compressive properties and degradation behavior as well as cytocompatibility of the prepared Zn-based scaffolds were systematically investigated to evaluate its potential for bone tissue engineering application.The results showed that the prepared Zn-based scaffolds with the two different porosities both present open porous structure and decent interconnectivity as well as a homogeneous pore distribution among 3D space.The scaffolds with the porosity of about 74%showed enhanced interconnectivity and thinner pore wall,however,the scaffolds with the porosity of about 68%showed higher yield stress and larger specific surface area.The addition of 3wt.%Cu not only improved the yield stress by 1 fold,but also accelerated the degradation rate by 4-6 folds,comparing to pure Zn scaffolds.In general,the Zn-based scaffolds prepared here possess excellent interconnectivity and similar mechanical properties to that of cancellous bone as well as moderate degradation rate,which makes them potential candidates for bone tissue engineering scaffolds.However,the relative higher in vitro cytotoxicity of the Zn-based scaffolds remains to be a tough problem,which should be settled urgently to meet the requirements of the tissue engineering scaffold.In order to improve the biocompatibility of the Zn-based scaffolds,we successfully prepared Mg-P and Ca-P bioactive coatings on the surface of the porous pure Zn scaffold.The two coatings both adhere tightly to the Zn substrate and the thickness of the Mg-P and Ca-P coatings are 10?m and 30?m leading to a porosity reduction of 5%and 20%,respectively.Even though,the coated scaffolds still maintain the open porous structure similar to that of naked scaffolds.The coated scaffolds present enhanced yield stress,significantly decreased releasing rate of Zn²⁺and hugely improved cytocompatibility.Particularly,the thicker Ca-P coating showed better cytocompatibility than the thinner Mg-P coating,and the Ca-P coated scaffolds could provide a suitable surface environment for the cell adhesion and proliferation even cultured for a long period.