Sirolimus-eluting dextran and polyglutamic acid hybrid coatings on AZ31 for stent applications

Abstract

Magnesium (Mg)-based cardiovascular stents are promising candidate as the next generation of novel stents. Clinical studies have revealed encouraging outcomes, but late restenosis and thrombogenesis still largely exist. Blood and vascular biocompatible coatings with drug-eluting features could be the solution to such problems. Objective This study was to investigate the feasibility of a three-layer hybrid coating on Mg alloy AZ31 with sirolimus-eluting feature for cardiovascular stent application. Materials and methods The first and third layers were low molecular weight dextran loaded with sirolimus, and the second layer was polyglutamic acid (PGA) to control sirolimus release. The hybrid coating was verified by scanning electron microscope (SEM). DC polarization and immersion tests were used to evaluate corrosion rate of the materials. Indirect cell viability and cell proliferation tests were performed by culturing cells with extract solutions of AZ31 samples. Blood compatibility was assessed using hemolysis assay. Results Coated samples had an enhanced corrosion resistance than that of uncoated controls, more PGA slower corrosion. Sirolimus had a burst release for the initial ∼3 days and then a slower release until reached a plateau. The PGA thickness was able to control the sirolimus release, the thicker of PGA the slower release. The overall cell viability was extract concentration-dependent, and improved by the hybrid coatings. Cell proliferation was correlated to coating thickness and was inhibited by sirolimus. In addition, all coated AZ31 samples were non-hemolytic. Conclusion Results demonstrated that such a three-layer hybrid coating may be useful to improve the vascular biocompatibility of Mg stent materials.