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.

Bioabsorbable zinc ion induced biphasic cellular responses in vascular smooth muscle cells

“…However, the main drawbacks of conventional Mg alloys are insufficient mechanical strength and rapid corrosion accompanied with hydrogen gas evolution, pH increase, and premature loss of mechanical integrity 5 . Previous studies on surface treatment 6 and element alloying 7 of Mg for stent application showed that these two methods enhanced the performance of Mg and its alloys at some degree but not sufficiently. More sophisticated efforts are in need to fully overcome such weaknesses of Mg materials.…”

Comparison of dextran‐based sirolimus‐eluting stents and PLA‐based sirolimus‐eluting stents in vitro and in vivo

“…(b)]. It has been reported that the dextran layer serves as both a matrix and a reservoir . Even though dextran is water‐soluble, it might initially affect the surrounding cells such as endothelial cells, and it may affect various biological cascades.…”

“…It has been reported that the dextran layer serves as both a matrix and a reservoir. 36 Even though dextran is water-soluble, it might initially affect the surrounding cells such as endothelial cells, and it may affect various biological cascades. Another study explored the effects of dextran on endothelial progenitor cells, and found that dextran could increase the expression of endothelial marker genes and endothelial cell-related transcription factor genes.…”

Advances in Antibacterial Functionalized Coatings on Mg and Its Alloys for Medical Use—A Review

“…They demonstrated that such a three-layer hybrid coating was useful to improve the vascular biocompatibility of Mg stent materials. In their study, biodegradable and nontoxic polymers, dextran, and polyglutamic acid (PGA) were used to fabricate protective coatings on Mg alloy AZ31 [45]. For the three-layer design, the first and third dextran layers served as the matrix and reservoir, and the middle PGA layer was used as the rate-controlling material.…”