Study on a new prospective coating for improving corrosion resistance of magnesium alloy stents with deformation

Biodegradable magnesium alloy vascular stents need to undergo complex deformation (crimping and expanding) in the body during implantation, which puts forward higher requirements for the protective coating material on stents. In this study, a drug-carrying polymer with larger elongation at break, poly(D,L-lactide-co-ε-caprolactone) (PLCL), was used as a new protective coating for AZ31 magnesium alloy stents to improve the corrosion resistance of the stents with deformations. PLCL coating was prepared on the surface of HF-treated AZ31 block samples by dip coating method to study the corrosion resistance of the alloy without deformation, while the conventional poly(D,L-lactide) (PDLLA) was used as a control. Through electrochemical and immersion tests, it was found that AZ31 samples with PLCL coating exhibited superior corrosion resistance. AZ31 stents with two different coatings prepared by ultrasonic spraying were crimped, expanded and immersed. The surface morphology and degradation behavior of the stents after the above deformation showed that the PLCL coating presented better mechanical adaptability to the stents with deformation, with reduced degradation rate, and especially, the pitting corrosion was inhibited. Meanwhile, the PLCL coating endowed great biocompatibility, which can be a promising protective coating for biodegradable magnesium alloy stents.