Bioresorbable drug-eluting magnesium-alloy scaffold: design and feasibility in a porcine coronary model

Abstract

Among three versions of bioresorbable magnesium scaffolds featuring different paclitaxel-elution kinetics, we determined the best-performing scaffold and compared it with established, paclitaxel-eluting, permanent stents TAXUS Liberté and eucaTAX. Drug-elution kinetics in magnesium scaffolds were modulated by varying the composition of their bioresorbable poly(lactide-co-glycolide) coating loaded with paclitaxel. A 50:50 ratio of lactide to glycolide, or an 85:15 ratio and either high- or low-molecular-weight polymer was applied in the "50/50", "85/15H", and "85/15L" scaffolds, respectively. Seventy-three magnesium scaffolds (25 50/50, 24 85/15H, 24 85/15L) and 36 control stents (18 TAXUS Liberté, 18 eucaTAX) were implanted in coronary arteries of 50 Yucatan mini-pigs. Angiography, histomorphometry, and histopathology data were acquired at 28, 90 and 180 days. The best-performing magnesium scaffold, 85/15H, was equivalent to TAXUS Liberté and superior to eucaTAX regarding late luminal loss, intimal area, fibrin score, and endothelialisation. Intimal inflammation score was higher in 85/15H than in the control stents at 28 days, but this effect disappeared at later time points. By selecting suitable paclitaxel-elution kinetics, it was feasible to develop a bioresorbable magnesium scaffold whose efficacy and healing characteristics in a porcine coronary model are comparable with those of established paclitaxel-eluting permanent metallic stents.