Coated metal stents

Kuiper KK, Robinson KA, Chronos NA, etal. Phosphorylcholine-coated metallic stents in rabbit iliac and porcine coronary arteries. Scand Cardiovasc J 1998 32(5) 261-268. 

Strecker EP Gabelmann A, Boos I, et al. Effect on intimal hyperplasia of dexamethasone released from coated metal stents compared with non-coated stents in canine femoral arteries. Cardiovasc Intervent Radiol 1998 21 487-496,... 

Yuan J, Gao R, Shi R, et al. Intravascular local gene transfer mediated by protein-coated metallic stent, Chin Med J (Engl) 2001 I 14(10) 1043-1045. 

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... 

According to ACC/AHA 2007 guidelines, clopidogrel is indicated for up to 12 months in NSTE ACS patients, with a minimum treatment duration of 1 month after placement of a bare-metal stent and 12 months after placement of a sirolimus- or paclitaxel-coated stent. 

A new trend in the delivery of medicines is to employ a device component. This may be an implantable pump for insulin, a metallic stent coated with a drug, or unit capable of rapidly vaporizing a discrete dose for inhalation. Such products are regulated by the FDA as "combination" products and may be reviewed by multiple Centers within the Agency, which may require additional levels of documentation to support the product design. 

Lambert T Dev V Rechavia E, Forrester J, Litvak p Eigler N. Localized arterial wall drug delivery from a polymer-coated removable metallic stent kinetics, distribution, and bioactivity offorskolin. Circulation 1994 90 1003-101 I. 

Schurmann K, Vorwerk D, Uppenkamp R, et al. Iliac arteries plain and heparin-coated Dacron-covered stent-grafts compared with noncovered metal stents-an experimental study. Radiology 1997 203(l) 55-63. 

See color plate) Effect of animal model and implant site on biologic response to polyurethane-coated stents. Comparable biologic responses to a bare-metal stent... 

B) in the rat subcutaneous model at 28 days. Dramatically different biological response to a bare-metal stent (C) and polyurethane-coated stent (D low magnification image) and (E high magnification image) in the porcine coronary artery model at 28 days. 

Galli et al. (63,64) demonstrated that primary stenting of AMI with PC-coated stent leads to excellent short- and midterm clinical outcomes and a low restenosis, despite a reduced heparin therapy. As in other studies, the reported restenosis rate using the BiodivYsio stent in the small vessels is lower than that using any other metallic stents (46,47, 49,64-68). 

Nevertheless, neointimal proliferation was not completely abolished by estradiol-eluting stents. It is possible that drug dosing, absorption, and elution kinetics, may have influenced our results and partially limited the antiproliferative effects of estradiol, Estradiol elution from hand -loaded PC-coated stents is only carried out within the first 24-hour interval. Nonetheless, the amount of intimal hyperplasia detected by IVUS in the present study compares favorably with bare metal stents (36), suggesting an antirestenotic effect of estradiol in spite of the suboptimal stent elution. 

Assessment of biologic/device combination product functionality needs to include all of the testing typically performed on bare metal stents (BMS). In the case of our antibody-coated stent model the BMS have been previously approved by CDRH, allowing some of the BMS data to be cross-referenced and not repeated when the effect of the antibody coating on the functionality of the device is considered negligible. These judgments must be made on a case-by-case basis and should be confirmed with the Office for Device Evaluation. 

Raina, T., Arnold, N., Moore, H., et al. 152 Stem cell coated metallic coronary stents show accelerated strut coverage without excessive neointimal proliferation in a porcine model. Heart 100, A88-A89 (2014)... 

Strecker, E.-P., Gabelmann, A., Boos, I., Lucas, C., Xu, Z., Haberstroh, J., Freudenberg, N., Strieker, H., Longer, M., and Betz, E., Effect on intimal hyperplasia of dexamethasone released from coated metal starts compared with non-coated stents in canine femoral arteries, Cardiovasc. Intervent. Radiol., 1998 21(6) 487-4%. 

In the periphery, the siroUmus-coated cordis self-expandable stent (SIROCCO) trial, a randomized, donble-bhnd study comparing sirolimus eluting stents to nitinol bare metal stents in patients with chronic limb ischemia caused by superficial femoral artery occlusions or stenoses, reported no difference between drag elntmg and bare metal stents. Both stent types improved the arterial brachial indices and claudication symptoms, and both stent types demonstrated similarly low restenosis rates (22.9% for sirolimus eluting stents vs 21.1% for nitinol bare metal stents p>0.05)... 

Tissue engineering Nerve regeneration Mimicking blood vessels Drug release applications Coating of metallic stents Surgical glue... 

Theoretically, reduced thrombogenicity of metallic stents and heart valve components might be achieved by thin film polymer coatings, although the clinical effectiveness of this strategy has not been demonstrated. Thus, chronic systemic anticoagulation is generally employed in patients with prosthetic heart valves (with metallic components) and stents. 

DESs have been the most recent breakthrough in stent technology. DESs consist of a metal stent covered with a thin polymer coating designed to improve vascular compatibility and elute antiproliferative agents. Drugs such as sirolimus (rapamycin) and paclitaxel serve to reduce restenosis by reducing hyperplasia caused by smooth muscle cell proliferation [37, 38]. 

Metallic stents have an established place in the management of patients with esophageal cancer. Stents provide better relief of dysphagia than all of other palliative methods available. Complications as a result of stenting remain a problem and the search goes on for better devices. Coated devices may offer the solution in the future. 

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