Biodegradable stents

However, permanent metallic implants have some drawbacks that limit their more widespread use. These limitations include long-term endothelial dysfunction, delayed re-endothelialization, thrombogenicity, permanent physical irritation, chronic inflammatory local reactions, mismatches in mechanical behavior between stented and non-stented vessel areas, inability to adapt to growth in young patients, and, importantly, non-permissive or disadvantageous characteristics for later surgical revascularization. 

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Schmidmaier G, Stemberger A, Alt E, Gawaz M, Schomig A, Time release characteristics of a biodegradable stent coating... 

Alt E, Beilharz C, Preter G, et al. Biodegradable stent coating with polylactic acid, hirudin and prostacyclin reduces restenosis [abstr], J Am Coll Cardiol 1997 29 238A. 

Yamawaki T Shimokawa H, Kozai T et al. Intramural delivery of a specific tyrosine kinase inhibitor with biodegradable stent suppresses the restenotic change of the coronary artery in pigs in vivo. J Am Coll Cardiol I 998 32 780-786. 

Landau C, Willard JE, Clagett GR et al. Biodegradable stents function as vehicles for vascular delivery of recombinant adenovirus vectors [abstr]. Circulation 1995 92(8) l-670. 

Biodegradable polymers, such as poly(L-lactic acid) (PLLA) and PLGA are suitable for drug-delivery applications due to their non-toxicity and adjustable biodegradability [25, 26]. PLGA and PLLA films have been used for the treatment of periodontal disease [27], glaucoma [28] and cancer [29], and as a component of biodegradable stents [30, 31]. 

Unverdorben, M. et al. Apolyhydroxybutyrate biodegradable stent preliminary experience in the rabbit. Cardiovasc Intervent Radiol. 2002,25(2), 127-132. 

Q. Guo, P.T. Knight, P.T. Mather, Tailored drug release from biodegradable stent coatings based on hybrid polyurethanes, J. Control. Release 137 (2009) 224-233. 

T. Tsuji, The influence of biodegradation of the biodegradable stent on vessel in long-term period serial intravascular ultrasound analysis of the Igaki-Tamai biodegradable stent, American heart association abstracts from scientific sessions. Circulation 106 (2002) 356. 

Reduced or abolished late stent thrombosis, facilitation of multiple surgeries in the lesion area, better imaging all these could be potential advantages of having a stent that actually disappears completely after it does its job. This led scientists to start developing fiiUy biodegradable stents (FBS) (Figure 4). 

Another example of a biodegradable stent is the REVA (Reva Medical Inc., San Diego, CA), a tyrosine-derived polycarbonate, which after metabolism produces amino acids, ethanol, and carbon dioxide. The REVA is balloon expandable with a slide and lock design which allows the expansion of the stent without deformation (Figure 5C). Iodine is its source of radiopacity. It has thick struts of 200 microns. Preclinical data show complete re-endothelialization [81]. Currently, the paclitaxel-eluting REVA stent is under development. 

Talja, M., Valimaa, T., Tammela, T., Petas, A., and Tormala, P. (1997) Bioab-sorbable and biodegradable stents in urology. /. Endourol, 11 (6), 391-397. Athanasiou, K.A., Niederauer, G.G., and Agrawal, C.M. (1996) Sterilization, toxicity, biocompatibility and clinical applications of polylactic acid/polyglycolic acid copolymers. Biomaterials, 17 (2), 93-102. 

Biodegradable stents with elastic memory. Biomaterials, 27 (8), 1573 — 1578. 

Recap and the Next Phase of Stent Evolution Biodegradable Stents... 

In order to better understand the challenges of biodegradable stent development, it is useful to first think about what a stent must endure during its lifetime. Thus an engineering point of view is outhned in this section to distil some of the key material requirements of biodegradable stents. 

Colombo, A. and Karvouni, E. (2000) Biodegradable stents Fulfilling the mission and stepping away . Circulation,... 

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