Dual strengthened corrosion control of biodegradable coating on magnesium alloy for vascular stent application

Recently, magnesium alloy vascular stents have aroused great attraction because of their biodegradability and good mechanical properties. However, the rapid degradation of magnesium alloy stents causes their premature collapse in clinical application. So far, there have been few magnesium alloy stent systems that achieved sufficient support time by using biodegradable coating. In this paper, a dual strengthened biodegradable coating on a AZ31b magnesium alloy stent was suggested to achieve stronger adhesion and lower water permeability. The composite coating consisted of a magnesium hydrate - magnesium fluoride (Mg(OH)2-MgF2) inorganic base layer constructed by a simple two-step solution immersion and a graphene oxide - poly(trimethylene carbonate) outer layer prepared by ultrasonic spraying. The biodegradable composite coating modified magnesium alloy exhibited an extremely low corrosion current density of 4.3 × 10−10 A·cm−2, which is five orders of magnitude lower than the unmodified magnesium alloy. In vitro immersion tests revealed that the modification can effectively reduce the corrosion rate of the magnesium alloy stent, and the modified magnesium alloy stent can support at least 8 weeks. Furthermore, in vitro biological experiment revealed the modification of the composite coating improved the biocompatibility and ensured good microenvironment for vascular repair. These results suggest that the biodegradable composite coating has great potential for application in vascular stent.