Functionalized carbon nanotube-encapsulated magnesium-based nanocomposites with outstanding mechanical and biological properties as load-bearing bone implants

Magnesium (Mg)-based composites have recently been studied as biodegradable material for the fabrication of orthopedic implants. Nevertheless, in physiological environments, proper mechanical properties and sufficient degradation rate are needed. In this paper, zinc (Zn) was uniformly distributed in the magnesium matrix using a ball milling process, and then the composite of Mg-3Zn/xfCNTs (x = 0, 0.2, 0.4, and 0.8 wt%) was successfully fabricated using a combination of semi-powder metallurgy, sintering and extrusion processes for use as a biodegradable load-bearing implant. The influence of functionalized carbon nanotubes (fCNTs) content on compressive strength, corrosion behavior and in vitro bioactivity (apatite formation ability and cytocompatibility) of the composite was investigated. The key toughening mechanisms that resist crack propagation include fCNTs pull-out, grain bridging by fCNTs, Crack branching and crack deflection. Furthermore, electrochemical and in-vitro immersion studies demonstrated that the corrosion behavior of Mg-3Zn composite under high concertation encapsulation was slightly reversed by fCNTs. Furthermore, cell culture investigations revealed that MG-63 cells present high level of cell viability and proliferate, implying that Mg-3Zn/0.4fCNTs composites are cytocompatible. All the findings suggest that the Mg-3Zn/0.4fCNTs composite with outstanding mechanical properties and appropriate corrosion resistance and biocompatibility may be a potential candidate for biodegradable implant application. © 2021 The Authors