2022, Vol. 26 ›› Issue (22): 3498-3504

Mechanical properties and biocompatibility of porous ZnO/hydroxyapatite composites with different porosities

Meng Zengdong1, Zhu Bin2, Zhang Yanan1, Luo Lilin3, Zhang Yuqin2   

Abstract: BACKGROUND: Earlier studies have found that adding zinc oxide to nano-hydroxyapatite and making it porous can significantly improve the apatite-forming ability and simultaneously have good biocompatibility, but the increase in porosity will lead to the deterioration of mechanical properties.
OBJECTIVE: To observe the changes in the microstructure, pore characteristics, mechanical properties, in vitro mineralization and degradation properties of porous zinc oxide/hydroxyapatite composites under different porosities, as well as the cell compatibility of the composites under suitable porosity.
METHODS: The porosity of the composite material was controlled by changing the added amount of pore former (medical grade ammonium bicarbonate). Porous zinc oxide/hydroxyapatite composite materials with different porosities (42%, 51%, 62%) were prepared by spark plasma sintering technology to study the microstructure, pore characteristics, mechanical properties, in vitro mineralization and degradation properties of three kinds of composite materials. Rabbit bone marrow mesenchymal stem cells were inoculated on the surface of porous zinc oxide/hydroxyapatite composite material with appropriate porosity, and cell adhesion and proliferation were observed.
RESULTS AND CONCLUSION:   (1) Scanning electron microscopy showed that with the increase of porosity, the number of pores in the composite material increased significantly; the through-hole structure increased; and microcracks appeared on the surface. The pore size of the composite material was between 0-500 μm. With the increase of porosity, compressive strength and elastic modulus of the composite were reduced; the compressive strength decreased from 148 MPa to 56 MPa; the elastic modulus decreased from 6.5 GPa to 3.5 GPa. (3) In vitro degradation and mineralization experiments showed that with improved composite surface porosity, bone apatite deposition species increased, and the degradation rate was accelerated. (4) Based on the above experimental results, the composite material with the porosity of 42% was selected to be co-cultured with rabbit bone marrow mesenchymal stem cells. The direct contact culture experiment showed that the cells grew and adhered well on the surface of the composite material and inside the void; the composite material extract CCK-8 assay showed that with the extension of culture time, rabbit bone marrow mesenchymal stem cells proliferated rapidly. (5) The results showed that the porous zinc oxide/hydroxyapatite composite material with the porosity of 42% had good mechanical properties, degradation properties and biocompatibility.
Key words: hydroxyapatite, porous, porosity, mechanical properties, apatites, degradation, cell adhesion, cell proliferation