HarvirHumpal_Drug Delivery-Patch

Drug Delivery-Patch Harvir Humpal

BMED 425-02

[email protected]

Problem Statement

• The user has been asked to develop a model for a transdermal drug delivery device. To ensure best design, we need a model to enable evaluation of various patch designs

• Surface concentration plots will be plotted at t=200,400,1000 s

• Line plot of drug concentration at the center of each layer and the outlet of the arteriole. (Include a zoomed-in view to show pulsatility)

• The maximum concentration (mol/m^3) for the center of each layer and the outlet of the arteriole will be calculated

• The time it takes to reach the maximum concentration for the center of each layer and the outlet of the arteriole will be calculated

• This will be done for both pulse and steady flow in arterioles

Mesh Description

• Type: Free Tetrahedral Mesh

• Fineness : Extra Fine

• Triangular Elements: 8006

• Quadrilateral Elements: 0

• Edge Elements: 1302

• Vertex Elements: 12

Assumptions and Given Data

• Assumptions • The thickness of the Epidermis and Stratus Corneum is around 0.5 mm

• The Pm of the Epidermis + Stratus Corneum is approximately 7.5 x 10-3cm/s.

• The arterial below the skin is 2 mm below the Epidermis/Stratus Corneum layer

• The diffusivity of the drug in the tissue between the skin layer and the arterial is approximately equal to the thickness of the dermis multiplied by the Pm of the dermis.

• The diffusivity in Blood is around 1e-5 m^2/s

• The Arteriole has an average blood velocity of 10 cm/s

Skin Layer Pm (cm/s) Thickness (cm)

Stratus

Comeum

7.23 x 10-3 1.49x10-3

Epidermis 7.77x10-3 0.1 to 1.3x10-2

Dermis 9.43x10-3 ~2.0e-1

Surface Plot of Steady Flow at t=200s

Surface Plot of Steady Flow at t=400s

Surface Plot of Steady Flow at t=1000s

Drug concentration line plot arteriole layer - steady flow

Drug concentration line plot dermis layer - steady flow

Drug concentration line plot patch layer - steady flow

Drug concentration line plot stratus corneum and epidermis layer -

steady flow

Maximum concentration and the time to the max. for each layer

(Steady Flow)

Layer Maximum Concentration (mol/m^3) Time to Maximum Concentration (s)

Arteriole 64.842 227

Dermis 209.553 227

SCE 560.618 214.5

Patch 999.899 200

Outlet 107.693 237

Surface concentration plot of pulsatile flow at t= 200 s

Surface concentration plot of pulsatile flow at t= 400 s

Surface concentration plot of pulsatile flow at t= 1000 s

Maximum concentration and the time to the max. for each layer using

pulsatile flow

Layer Maximum Concentration (mol/m^3) Time to Maximum Concentration (s)

Arteriole 68.135 224

Dermis 206.130 226.5

SCE 547.038 215

Patch 1000.179 200

Outlet 105.529 234.5

[Drug concentration line plot – zoomed in] 5 layers – pulsatile flow

[Drug concentration line plot] 5 layers – pulsatile flow

Conclusions, Future Directions

• The pulsatile flow model hadmaximum concentration values were slightly lower than those of the steady flow model.

• There are no real errors on this lab. However, the assumptions that were used simplified this lab and aren’t an exact indication of what the true values of shear stress and the avg. velocity are.

• The calculated values of velocity, shear stress, and concentration can be used to calculated to analyze other aspects of these vessels such as volumetric flow rate or the stress that a medical device will need to account for.

• The values that we obtained can be used for different organic systems such as the heart.