30 March 2010 Mathematical modeling for the design of porous coronary stents: nano- and microporous stents v. macroporous stents
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Abstract
Drug delivery polymers play a role in late in-stent thrombosis of first generation drug-eluting coronary stents (DES) via an inflammatory reaction, which contributes to delayed endothelialization seen in patients with late stent thrombosis. Subsequent generation DES have non-polymer based DES whose surface pores serves as a drug reservoir. While drug elution for pores in the nanometer range have been shown to be comparable to polymer-based DES in terms of luminal renarrowing (i.e restenosis), how different pore sizes effect drug elution has not been fully characterized. We hypothesized that drug elution can be characterized with a mathematical model that takes into account the pore size of the stents and molecular characteristics of the eluted drug. Structural data from porous, non-polymer based stents were examined with pore radius ranging from the nanoporous to macroporous range (5 nm to > 10 mm). All stents eluted tacrolimus, sirolimus or paclitaxel. A mathematical model based on Stefan-Maxwell equations describing the mass transport of molecules through a porous media was constructed. A dimensionless number was derived characterizing molecular flux of the drugs through a porous membrane. It was observed that there was exponential rise in molecular flux of the eluted drug with pore sizes greater than 5 micrometers. The molecular characteristics of the eluted drug did not affect the molecular flux. In conclusions, stents in the nano- and microporous range will have similar drug elution profiles while macroporous stents will vary greatly. Careful attention to pore size may significantly enhance the design and efficacy of porous polymer free stents.
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Anwer K. Habib, Anwer K. Habib, Aloke V. Finn, Aloke V. Finn, } "Mathematical modeling for the design of porous coronary stents: nano- and microporous stents v. macroporous stents", Proc. SPIE 7646, Nanosensors, Biosensors, and Info-Tech Sensors and Systems 2010, 76461E (30 March 2010); doi: 10.1117/12.852707; https://doi.org/10.1117/12.852707
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