Skin is the largest organ of the human body and due to its immediate proximity to the environment is often exposed to a variety of extraneous chemicals. A proper study of percutaneous absorption is critical to the risk assessment pertaining to variety of exposure scenarios (occupational and environmental) and also for the development of transdermal products (cosmetic and therapeutic). The number of chemicals to which the human population can be exposed is extremely high such that only a small fraction can be studied experimentally. Thus, computational models for dermal absorption used in lieu of animal experiments to estimate absorption of new ingredients are used widely in many industries. The exposure scenario for volatile chemicals is further complicated due to a vigorous evaporation that influences its tendency to penetrate.
This dissertation discusses the development of a mathematical model for predicting skin permeability of volatile compounds using the fundamental principles of transport phenomena and thermodynamics. The key features of the model include treatment of the moving boundary (finite dose volumes), treatment of multilayered problems, convection due to density gradients (binary and multicomponent systems), etc. and ascertaining the system parameters using information obtained from the intricate skin microstructure and mechanisms of permeation. These models are then validated through comparing the respective simulation results with corresponding experimental data on the skin permeation fluxes of pure ethanol and benzene. Optimal values of sensitive parameters are obtained through extensive non-linear regression analysis and compared with the original predictive values. The results show appreciable correlation between the model predictions and the experimental data (fraction of dose absorbed). It was also clear that the disposition characteristics of low-molecular weight volatile liquids are critically dependent on parameters such as the fractional deposition depth and skin diffusivity. Also, in order to mimic the behavior of penetrating compounds from cosmetic and pharmaceutical formulations, a binary mass-transfer model is developed. This is then validated by comparing the simulation results with experimental skin permeation data on benzyl alcohol (BA) from a dilute ethanolic solution. The fraction absorbed for BA is not independent of the fractional deposition depth but is sensitive to skin diffusivity.
|Advisor:||Krantz, William B.|
|School:||University of Cincinnati|
|Department:||Engineering : Chemical Engineering|
|School Location:||United States -- Ohio|
|Source:||DAI-B 79/10(E), Dissertation Abstracts International|
|Keywords:||Mathematical modeling, Percutaneous absorption, Skin, Transdermal transport, Volatile chemicals|
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