The influence of silane and silane–PMMA coatings on the in vitro biodegradation behavior of AE42 magnesium alloy for cardiovascular stent applications

Abstract

The squeeze-cast alkali pretreated (NaOH, 3 M, 10 days) AE42 Mg alloy is coated with silane as well as silane–polymethylmethacrylate (PMMA) by a sol–gel technique. The detailed microstructural characteristics, adhesion strength and in vitro corrosion behavior using hydrogen evolution, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) of the coatings in simulated body fluid (SBF) under both static and dynamic conditions for 7 days has been systematically investigated. In addition, contact angle, protein adsorption and hemocompatibility of all the specimens have also been studied to establish their significance for cardiovascular stent application. For comparison, the same has also been carried out on the uncoated AE42 alloy. The coated specimens showed improvement in hydrophobicity leading to their corrosion resistance. The results of EIS, pH variation and Mg²⁺ ion release confirm that the silane–PMMA coating has the lowest in vitro biodegradation under both static immersion and dynamic flow conditions. Further, the protein adsorption and hemocompatibility results depict enhanced biocompatibility of the silane–PMMA-coated specimen making it a favorable candidate for biodegradable stent applications.