Investigation on magnesium degradation under flow versus static conditions using a novel impedance-driven flow apparatus

This article reports a novel impedance-driven flow apparatus and its applicability for studying magnesium degradation under flow versus static conditions. Magnesium has potential to be an effective biomaterial for use inside the human body due to its biodegradability and biocompatibility. Magnesium undergoes degradation reactions in aqueous solutions such as body fluids, leading to mass loss and pH increase of the surrounding fluid. To compare the degradation process of magnesium under flow versus static conditions, a novel flow apparatus consisting of an impedance pump and a flow chamber was designed and constructed. In addition to low-cost, this apparatus is flexible to be sterilized and assembled, and is small enough for use inside an incubator, making it appealing for measuring and comparing magnesium degradation in vitro under flow versus static conditions. The average flow rate in this flow apparatus was 2.8 ml/s, mimicking the flow rate (2.6 ml/s) in coronary artery. In a simulated body fluid (SBF), magnesium samples lost their mass at a much faster rate under the flow condition than that under the static condition. Starting with a pH of 7.4, the SBF showed a pH increase to 8.5 under the flow condition within 96 h due to the degradation of magnesium, greater than the pH increase under the static condition. The results of this study demonstrated the effects of fluid flow on magnesium degradation using the impedance-driven flow apparatus, providing useful design guidelines for magnesium-based implants that may be exposed to body fluid flow.