Polymeric coated stents

Administration (FDA) approval of SIBS, used as the polymeric coating on the Taxus coronary stent, opened new avenues for polyisobutylene-based TPEs in biomedical engineering. 

Holmes DR, Camrud AR, Jorgenson MA, Edwards WD, Schwartz RS. Polymeric stenting in the porcine coronary artery model differential outcome of exogenous fibrin sleeves versus polyurethane-coated stents. J Am Coll Cardiol 1994 24(2) 525-531. 

Polymeric coating designs in drug-eluting stent... 

When a similar plasma polymerization coating was applied on the surface of a memory-expandable stainless steel stent, whose bare surface has notoriously poor blood compatibility, and implanted in a pig without using any drug to suppress blood coagulation, all five coated samples stayed patent, whereas uncoated stents with drug showed partial to total closure [7]. Such a clear-cut result, i.e., 5 out of 5 patency, has been scarcely seen in any animal experiments, which again seems to indicate the superior biocompatibility of imperturbable surfaces created with LCVD coatings. 

Massey et al. studied the influence of LEE irradiation on plasma polymerized allylamine (Massey et al. 2010) and fluorocarbon (Massey et al. 2008b) coatings for stent applications to simulate irradiation conditions of implanted coated stents in the human body dnring diagnostic exposure to... 

Bioabsorbable polymeric stents can trigger acute or chronic inflammatory responses due to the degradation of the stent. The vascular response to a fully bioabsorbable stent can be more different than that of a metal- or polymer-coated stent. Polymers are listed in Table 7.5. Anti-inflammatory drugs are listed in Table 7.6. 

Bakhshi, R., Darbyshire, A., Evans, J.E., You, Z., Lu, J., Seifalian, A.M., 2011. Polymeric coating of surface modified nitinol stent with POSS-nanocomposite polymer. Colloids and Surfaces B Biointerfaces 86, 93-105. 

The coating materials for stents can be broadly classified into four types inorganic materials, polymers, porous metals, and endothelial cells. In this work, we will focus on polymeric coatings, putting special focus on polyurethanes. The main function of the coating is to reduce the incidence of early and late stage thrombosis and restenosis during stent placement. 

In some cases, the polymeric systems may need to effectively prevent cellular adhesion. In particular, VEGF delivery systems in contact with blood (e.g., polymeric coatings of vascular stents) must prevent unspecific adhesion of... 

A number of randomized clinical trials (RCTs) have investigated stent-based delivery of paclitaxel. These studies utilized a number of different delivery methods, including polymeric sleeves, nonpolymeric drug delivery and from drug-polymer coatings on stents. 

Massey, S., E. Gallino, P. Cloutier et al. 2010. Low-energy electrons and x-ray irradiation effects on plasma-polymerized allylamine bioactive coatings for stents. Polym Degrad Stab 95 153-163. 

The discovery of living cationic polymerization has provided methods and technology for the synthesis of useful block copolymers, especially those based on elastomeric polyisobutylene (Kennedy and Puskas, 2004). It is noteworthy that isobutylene can only be polymerized by a cationic mechanism. One of the most useful thermoplastic elastomers prepared by cationic polymerization is the polystyrene-f -polyisobutylene-(>-polystyrene (SIBS) triblock copolymer. This polymer imbibed with anti-inflammatory dmgs was one of the first polymers used to coat metal stents as a treatment for blocked arteries (Sipos et al., 2005). The SIBS polymers possess an oxidatively stable, elastomeric polyisobutylene center block and exhibit the critical enabling properties for this application including processing, vascular compatibility, and biostability (Faust, 2012). As illustrated below, SIBS polymers can be prepared by sequential monomer addition using a difunctional initiator with titanium tetrachloride in a mixed solvent (methylene chloride/methylcyclohexane) at low temperature (-70 to -90°C) in the presence of a proton trap (2,6-dt-f-butylpyridine). To prevent formation of coupled products formed by intermolecular alkylation, the polymerization is terminated prior to complete consumption of styrene. These SIBS polymers exhibit tensile properties essentially the same as those of... 

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