Tetra-functional multilayer coatings for cardiovascular stent materials

Functional coatings have been of great interest in enhancing the performance of implants in recent years. Here, for the first time, preparation and characterization of a tetra-functional coating is reported, exhibiting anticorrosion, antibacterial, biocompatible, and anticoagulant behaviors. Poly(2-ethyl-2-oxazoline)-copolyethyleneimine (PEOX-co-PEI) stabilized silver nanoparticles (AgNPs) and heparin were used to prepare the multifunctional multilayers. The coatings were deposited on nitinol and 316 L stainless steel substrates, the most used materials in coronary stents, via layer-by-layer (LbL) technique. Corrosion current density values obtained from Tafel plots are 1.61 x 10-9 A/cm2 and 6.79 x 10-8A/cm2 for coated and uncoated 316 L substrate, respectively. Similarly, the corrosion current density values shifted from 1.00 x 10-8A/cm2 for uncoated nitinol to 4.77 x 10-10A/cm2 after coating. Contact killing method against gram-positive (Staphylococcus aureus) and gram-negative (Pseudomonas aeruginosa) bacterial species concluded that the presence of the coating on the surfaces of the materials reduces the number of the survived colonies (in CFU/mL) for more than 99.9%independent of the underlying metal within 3 hours of incubation time. Prepared coatings demonstrated above 90% relative viability compared to the positive control in MTT assay using human umbilical vein endothelial cells (HUVEC), indicating no cytotoxic effect on adjacent healthy cells. The coagulation assay also exhibited a 50% reduction in the coagulation rate after coating compared to the bare substrates, confirming the antithrombogenicity of the coatings.