Physiological consequences of half-embedded drug-eluting stent on coronary drug-transport: A two-species drug delivery simulation

Abstract

Drug-eluting stent (DES) is commonly utilized to open blocked arteries and reduce in-stent restenosis (ISR) brought on by the implantation of bare-metal stent (BMS). The current mathematical model sheds light on investigating the physiological effects of different clinical parameters on drug distribution and retention within the artery wall. A two-dimensional (2D) axisymmetric cylindrical model of a typical Palmaz stent having circular struts coated with a bio-durable polymer is half-embedded in the tissue. This investigation considers two distinct drug phases - the unbound and bound phases - in the artery wall. The artery wall is considered a porous medium, and the Brinkman equation governs the interstitial fluid (ISF) flow within it. An unsteady convection-diffusion-reaction mechanism governs unbound drug transport, while that of bound drug is solely controlled by an unsteady chemical reaction. The drug delivery system also includes a reversible equilibrium mechanism to maintain the chemical reaction between the drug molecules and the receptors. Drug and momentum transport equations are solved using the Marker-and-Cell (MAC) method in staggered grid setups with appropriate initial and boundary conditions. According to simulations, there is going to be a bi-phasic decrease in unbound drug in the artery wall with a larger binding-on constant (ψ), and the concentration of both drug forms and the area under concentration decrease as the Peclet number (Pe) increases. Additionally, as the equilibrium association constant ($k_{eq}$) increases, the concentration of the unbound drug decreases, but the tendency for the bound drug is reversed. The sensitivity of some significant parameters has been examined in a thorough sensitivity study. Our results are in excellent agreement with the findings available in the literature.