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POSS-Containing Nanocomposite Polymer Coatings
Published in Vikas Mittal, Polymer Nanocomposite Coatings, 2016
Yasmin Farhatnia, Aaron Tan, Alexander M. Seifalian
The most important characteristic of the polymer coating is that it must be biocompatible. For instance, the endeavor stent uses a phosphorylcholine polymer, which is associated with biological membranes. The polymer coating also aids in controlled release of drugs. Polyvinyl pyrrolidone in the endeavor resolute increases the initial drug burst due to its hydrophilicity, thus enhancing the elution rate. Layers of different polymers can also be employed, as seen in the CYPHER stent. It uses a parylene C basecoat, with the next coating made up of polyethylene-co-vinyl acetate, and poly n-butyl methacrylate (PBMA) mixed with sirolimus. A topcoat of drug-free PBMA is then layered to aid in the controlled release of sirolimus.
Durable polymer everolimus-eluting stents: history, current status and future prospects
Published in Expert Review of Medical Devices, 2020
Juan J. Rodríguez-Arias, Luis Ortega-Paz, Salvatore Brugaletta
These new stents use a more biocompatible and thinner polymer; 7.8 μm compared to 13.7 μm in the Cypher stent. The primary layer is composed of a nonerodable polymer made of poly-N-butyl methacrylate (PBMA) and is in charge of the adhesion of the drug coating layer. The reservoir is made of a fluorinated copolymer of vinylidene fluoride and hexafluoropropylene monomers (PVDF-HFP), which contains 100 μg/cm2 of everolimus for all stent sizes with a ratio of 83%/17% for polymer/everolimus respectively and no topcoat. 80% of the drug is released during the first month and the rest during the next four months [32]. (SeeFigure 1) Another characteristic of this material is its high biocompatibility based on a protein-rich layer on the surface with a high albumin to fibrinogen ratio. It also contains a fluorine-rich surface that has been demonstrated to be non-thrombogenic and biocompatible [33,34]. The evolution of percutaneous coronary treatment options can be seen in Figure 3.