In vitro degradation, hemolysis and MC3T3-E1 cell adhesion of biodegradable Mg-Zn alloy

In this study a kind of patent binary Mg-6 wt.%Zn magnesium alloy was investigated as degradable biomedical material. The results of in vitro degradation including electrochemical measurements and immersion tests in simulated body fluid (SBF) revealed that zinc could elevate both the corrosion potential and Faraday charge transfer resistance of magnesium and thus improve the corrosion resistance. XRD and EDS analysis proved that the corrosion products on the surface of Mg-Zn contained hydroxyapatite (HA), Mg (OH)(2) and other Mg/Ca phosphates, which could reduce the degradation rate. The degradation process of magnesium alloy and the mechanism of corrosion layer formation were also discussed in this work, i.e. the byproducts of degradation of magnesium, Mg2+ and OH-, reacted with the phosphate and Ca2+ in the SBF, thus the corrosion layer containing HA, Mg(OH)(2) and other magnesium-substituted apatite precipitated in corrosion pits and covered the surface of magnesium alloy. The hemolysis test found that the hemolysis rate of Mg-Zn was 3.4%, which is lower than the safe value of 5% according to ISO 10993-4. For the cell culture experiments, after 2 h incubation the pre-osteoblastic cell MC3T3-E1 was able to adhere and spread on the corrosion layer of Mg-Zn alloy, indicating that despite the fluctuation of pH value of DMEM culture solution, Mg-Zn alloy could still support the earlier adhesion of pre-osteoblastic cells on the surface. Hemolysis and adhesion of cells display good biocompatibility of Mg-Zn alloy in vitro. (C) 2009 Elsevier B.V. All rights reserved.