Effect of Surface-Modification on In Vitro Corrosion of Biodegradable Magnesium-Based Helical Stent Fabricated by Photo-chemical Etching

Abstract

During the last decade, magnesium and its alloys have been extensively studied to develop a new generation of biodegradable medical implants. The fast degradation rate of pure magnesium and related alloys in the physiological environment poses significant challenges to devices made of these materials for biomedical applications. In this study, we have designed and fabricated biodegradable helical stents made of AZ31 magnesium alloy, and have explored theirs in vitro corrosion behavior in Dulbecco's Modified Eagle's Medium (DMEM). The corrosion rate was significantly reduced by surface modifications of the helical stent, achieved through applying a biocompatible Parylene C polymer coating, or via chemical etching of the devices in inorganic solutions. The corrosion rates of the coated AZ31 Mg helical stents were compared, with uncoated samples used as a control. The results achieved indicated that all tested surface modifications successfully inhibited metal corrosion rates in vitro. Materials coated with Parylene C coating revealed a maximum corrosion rate reduction of 70% to 85% in DMEM solution.

Plasma Electrolytic Oxidation of Az31 Magnesium Stents for Degradation Rate Control

“…Most of these devices have been tested in vitro and in vivo. Details about the device fabrication using photo-chemical etching of biodegradable metal sheets have been previously published by the Cincinnati group [17][18][19]. The starting material was a rectangular sheet of AZ31 (99.9 %) with dimensions 250 mm × 250 mm and a thickness of 250 μm (Goodfellow, Oakdale, PA).…”

“…The photo-chemical etching method transfers a selected pattern of the stent onto the metal sheet followed by chemical etching Fig. 1 [19].…”