Mechanical Properties, Degradation Behavior, and Cytocompatibility of Zn-Mg-Graphene Nanoplatelets Composite for Orthopedic-Implant Applications

Zinc (Zn)-based materials reveal inadequate mechanical properties as orthopedic biodegradable implantable materials, which limits their biomedical applications. Herein, Zn-xMg (magnesium) composites (x = 0.5, 1.0, 1.5, and 2.0 wt%) reinforced with 0.2 wt% graphene nanoplatelets (GNP) are obtained via powder metallurgy and hot-pressing sintering. The addition of 0.5-2.0 wt% Mg into Zn-0.2 wt% GNP composite resulted in the formation of Mg2Zn11 and MgZn2 phases without any additional intermetallic carbide phases. The hot-pressing sintered (HPS) Zn-0.5Mg-0.2GNP composite exhibits a compressive yield strength of 169 +/- 18 MPa, an ultimate compressive strength of 270 +/- 39 MPa, a compressive strain of 17 +/- 6%, and a microhardness of 86 +/- 2 HV. Electrochemical corrosion testing reveals that corrosion resistance of HPS Zn-xMg-0.2GNP composites decreases with increasing Mg content, while immersion tests in Hanks' balanced salt solution for 30 d indicate that the degradation rate increases from 0.032 to 0.141 mm y(-1) by increasing Mg content from 0 to 2.0 wt%. In vitro cytotoxicity assessments using SaOS2 human osteoblast cells show >90% viability following exposure over 5 d to 12.5% extract concentrations of all HPS composites. The HPS Zn-0.5Mg-0.2GNP composite exhibits the appropriate material properties for biodegradable bone-implant applications.