On the transport through polymer layer and porous arterial wall in drug-eluting stents
Journal of the Brazilian Society of Mechanical Sciences and Engineering
ABSTRACT:
The safety and efficacy of drug-eluting stents are strongly influenced by the transport of the antiproliferative/anti-inflamma- tory drugs in the arterial wall. Dissolution in the polymer coating and specific binding in the artery wall play an important role in the process. We consider the model of dissolution, transport and binding of sirolimus on an axisymmetric domain representing the polymer coating layer and the porous artery wall in the vicinity of a stent strut. We employ the FEM on an unstructured mesh to discretize the governing equations. We employ a nonlinear dissolution model for the dynamics in the coating, and a nonlinear saturable binding model that includes both specific and non-specific binding in the arterial wall as separate phases, as proposed by McGinty and Pontrelli (J Math Chem 54:967–976, 2016). The arterial wall is considered an anisotropic porous media, and the flow is considered to be governed by Darcy flow. The permeability in the polymer coat- ing is considered to be very small, but finite. The endothelium lamina, where present, is modelled as a no-flow boundary. The effect of slow and fast release polymers is considered, showing that the time evolution of the process can be efficiently controlled by the polymer diffusion coefficient. In fact, an order of magnitude decrease in the polymer diffusion coefficient results in an order of magnitude increase in the time of drug delivery. It is estimated that 52–54% of the sirolimus mass actually diffuses into the arterial wall. However, the spatial distribution of the sirolimus is greatly influenced by the flow and the arterial wall properties, being therefore susceptible to patient health conditions.