Porous Medium Modeling of Combined Effects of Cell Migration and Anisotropicity of Stratum Corneum on Transdermal Drug Delivery

A numerical model for transdermal drug delivery (TDD) has been developed by treating skin as a composite, dynamic, porous medium. Governing unsteady mass transport equations in porous medium was solved for different cases for up to a period of drug-patch application of 10 hrs. The effects of cell migration and anisotropic diffusive properties of stratum corneum (SC) on TDD are analyzed. Each of the above factors and their combination are found to significantly affect TDD. The cell migration in SC decreases the predicted amount of drug considerably. Their combined effect in TDD helped in identifying four distinct regimes of pharmacological as well as engineering importance within the domain

Experimental and Numerical Determination of Interface Slip Coefficient of Fluid Stream Exiting a Partially Filled Porous Medium Channel

Stacks of parallel plates modeled as a standard fissure-type anisotropic porous medium are filled inside a rectangular channel up to half the cross section height. The interface slip coefficient a for the isothermal laminar incompressible flow exiting this partially filled porous-medium channel is then determined using particle image velocimetry (PIV) experiments and numerical simulations. Required measurements of the Darcy velocity u D on the porous-medium (PM) side, the local velocity u f , and its gradient @u f =@y on the clear-fluid (CF) side are performed across different length scales. The fissure-type porous-medium parameters are systematically varied in the porosity range 0:2 / 0:95 and flow direction permeability 10 À6 < K; m 2 < 10 À9 . From the exit-velocity profile, the empirical slip coefficient a is determined using a generalized relationship. When the measurements across the PM-CF interface are performed across a length scale equal to the representative elemental length (REL) of the porous media considered (i.e., equal to the sum of plate thickness (a) and gap (b)), the determined a value is found to remain invariant

Macromolecular Transport Through Porous Arterial Walls

Arteries are heterogeneous, composite structures that undergo large cyclic deformations during blood transport. Presence, build-up and consequent rupture of blockages in blood vessels, called atherosclerotic plaques, lead to disruption in the blood flow that can eventually be fatal. Abnormal lipid profile and hypertension are the main risk factors for plaque progression. Treatments span from pharmacological methods, to minimally invasive balloon angioplasty and stent procedures, and finally to surgical alternatives. There is a need to understand arterial disease progression and devise methods to detect, control, treat and manage arterial disease through early intervention. Local delivery through drug eluting stents also provide an attractive option for maintaining vessel integrity and restoring blood flow while releasing controlled amount of drug to reduce and alleviate symptoms. Development of drug eluting stents is hence interesting albeit challenging because it requires an integration of knowledge of mechanical properties with material transport of drug through the arterial wall to produce a desired biochemical effect. Although experimental models are useful in studying such complex multivariate phenomena, numerical models of mass transport in the vessel have proved immensely useful to understand and delineate complex interactions between chemical species, physical parameters and biological variables. The goals of this review are to summarize literature based on studies of mass transport involving low density lipoproteins in the arterial wall. We also discuss numerical models of drug elution from stents in layered and porous arterial walls that provide a unique platform that can be exploited for the design of novel drug eluting stents