Optimizing Polycaprolactone Coating on We43 Magnesium Alloy for Biodegradable Stent Applications: A Comprehensive Study Using Dual Solvents, Ultrasonic Atomization Spray, and Anodization Techniques

WE43 magnesium-based alloy is modified and investigated for biodegradable gene-eluting stent applications as it is an ideal engineering material with good mechanical properties and offers better biocompatibility compared to aluminium/zinc (AZ) alloys. In this work, polycaprolactone (PCL) is coated on WE43 using two different solvents via ultrasonic atomization spray coating. For better adhesion of this PCL to the surface, anodization was performed on WE43 to increase bonding strength. Spray coating parameters such as solution concentration, number of spray passes, atomizing power, etc., were optimized for best coating performance. Characterizations on the coatings showed that both acetone and dichloromethane are suitable for spray coating PCL, but acetone is slightly better, and it is also safer and easier to use. The porous microstructure of oxides formed by anodization increased the bonding adhesion between PCL and WE43. PCL covering these oxides led to enhanced anticorrosion properties as this hydrophobic polymer decreased the water uptake and increased the corrosion resistance. This significantly enhanced corrosion resistance also maintains the mechanical properties of the WE43 as the mass loss decreased by a factor of four times after PCL coating, helping to keep the mechanical integrity of WE43. Having the oxide layer beneath PCL coating prevented it from peeling off. Subsequent in vitro cell viability results showed that the PCL layer enhanced the viability of HAoEC cells.