In this study a binary Mg-Zn magnesium alloy was researched as a degradable biomedical
material. An Mg-Zn alloy fabricated with high-purity raw materials and using a clean
melting process had very low levels of impurities. After solid solution treatment
and hot working the grain size of the Mg-Zn alloy was finer and a uniform single phase
was gained. The mechanical properties of this Mg-Zn alloy were suitable for implant
applications, i.e. the tensile strength and elongation achieved were approximately
279.5MPa and 18.8%, respectively. The results of in vitro degradation experiments
including electrochemical measurements and immersion tests revealed that the zinc
could elevate the corrosion potential of Mg in simulated body fluid (SBF) and reduce
the degradation rate. The corrosion products on the surface of Mg-Zn were hydroxyapatite
(HA) and other Mg/Ca phosphates in SBF. In addition, the influence caused by in vitro
degradation on mechanical properties was studied, and the results showed that the
bending strength of Mg-Zn alloy dropped sharply in the earlier stage of degradation,
while smoothly during the later period. The in vitro cytotoxicity of Mg-Zn was examined.
The result 0-1 grade revealed that the Mg-Zn alloy was harmless to L-929 cells. For
in vivo experiments, Mg-Zn rods were implanted into the femoral shaft of rabbits.
The radiographs illustrated that the magnesium alloy could be gradually absorbed in
vivo at about 2.32mm/yr degradation rate obtained by weight loss method. Hematoxylin
and eosin (HE) stained section around Mg-Zn rods suggested that there were newly formed
bone surrounding the implant. HE stained tissue (containing heart, liver, kidney and
spleen tissues) and the biochemical measurements, including serum magnesium, serum
creatinine (CREA), blood urea nitrogen (BUN), glutamic-pyruvic transaminase (GPT)
and creatine kinase (CK) proved that the in vivo degradation of Mg-Zn did not harm
the important organs. Moreover, no adverse effects of hydrogen generated by degradation
had been observed and also no negative effects caused by the release of zinc were
detected. These results suggested that the novel Mg-Zn binary alloy had good biocompatibility
in vivo.