Heparin-Loaded Composite Coatings on Porous Stent from Pure Magnesium for Biomedical Applications

Challenges associated with drug-releasing stents used in percutaneous transluminal coronary angioplasty (PTCA) encompass allergic reactions, prolonged endothelial dysfunction, and delayed stent clotting. Although absorbable stents made from magnesium alloys seem promising, fast in vivo degradation and poor biocompatibility remain major challenges. In this study, zirconia (ZrO₂) layers were used as the foundational coat, while calcium phosphate (CaP) served as the surface layer on unalloyed magnesium specimens. Consequently, the corrosion current density was decreased to 3.86, from 13.3 μA/cm². Moreover, a heparin-controlled release mechanism was created by co-depositing CaP, gelatin (Gel), and heparin (Hep) on the specimens coated with CaP/ZrO₂, thereby boosting magnesium's blood compatibility and prolonging the heparin-releasing time. Techniques like X-ray diffractometry (XRD), focused ion beam (FIB) system, toluidine blue testing, UV-visible spectrometry, field emission scanning electron microscopy (FESEM), and surrogate tests for endothelial cell viability were employed to examine the heparin-infused coatings. The drug content rose to 484.19 ± 19.26 μg/cm² in multi-layered coatings (CaP-Gel-Hep/CaP-Hep/CaP/ZrO₂) from 243.56 ± 55.18 μg/cm² in a single layer (CaP-Hep), with the controlled release spanning beyond 28 days. Also, cellular viability assessments indicated enhanced biocompatibility of the coated samples relative to those without coatings. This suggests the potential of magnesium samples after coating ZrO₂ and CaP with Gel as candidates for porous biodegradable stents or even scaffolds in biomedical applications.