In Vitro Dynamic Degradation Behavior Of Mg Alloys In The Presence Of Proteins

Magnesium and its alloys have drawn wide attention as new type of degradablebiomaterials due to their excellent mechanical property as well as biocompatibility.However, the unbefitting corrosion degradation behaviour of Mg alloys in physiologicalenvironment inhibits the rapid development as biomedical materials. It is hard tocompletely solve the rapid in vivo bio-corrosion up to now. Therefore it is significant toillustrate the in vitro or in vivo degradation mechanism of Mg alloys. Based on this reason,the investigation about the degradation behaviour of Mg alloys in the flowing simulatedbody fluids with or without albumin has been carried out to make a systematic comparison.In this paper, AZ31and Mg-Ca alloys were used to investige the synergistic influence offlow, protein, and CO₂on the degradation behaviour of biomedical magnesium alloys inphysiological environment. There types of testing simulated body fluids were applied, andthe main results are as follows:Firstly, synergistic influence of flow and albumin on in vitro degradation behaviour ofMg alloys in simulated body fluids was investigated. The results indicate that thedegradation rate of AZ31and Mg-Ca alloys is significantly enhanced with increasing theflowing rate of test solutions. However, in contrast to the results obtained from static tests,the addition of bovine serum albumin can intensify the corrosion attack in dynamic testingconditions.Secondly, the experiments in flowing simulated body fluid with and without fetal bovineserum were also carried out to measure the synergistic effects of flow and serum proteinson the corrosion degradation behavior of Mg alloys. In comparison with the results in statictest solutions, higher corrosion rate was measured through potentiodynamic polarizationtest and weight loss examination in the presence of serum proteins. Moreover, the resultsfrom electrochemical impedance spectra further indicate the adverse influence of serumproteins on the corrosion behavior of AZ31and Mg-Ca alloy under dynamic testingconditions. Finally, synergetic influence of flow, albumin and CO₂on the initial corrosiondegradation behavior of Mg alloy in artificial physiological environment was studied byelectrochemical techniques. The corrosion attack of AZ31and Mg-Ca alloy wasaggravated by the existence of albumin and CO₂. The flow of testing fluids can shift thealbumin from corrosion inhibitor to a corrosion accelerator, resulting in higher corrosionrate. Furthermore, the addition of albumin in CO₂saturated solutions can further aggravatethe corrosion of AZ31and Mg-Ca alloy in static test solutions, while slightly reduce thecorrosion rate in dynamic experiments.Based on the aforementioned experimental results, it is suggested that proteins canprotect the specimen surface from corrosion attack under static test solutions, whileaccelerate corrosion of magnesium alloy under dynamic testing conditions, and moreover,CO₂can accelerate the corrosion rate of magnesium alloy in the initial corrosion stage.