Compartmental modeling of skin absorption and desorption kinetics: Donor solvent evaporation, variable diffusion/partition coefficients, and slow equilibration process within stratum corneum.

This work expands the recently developed compartmental model for skin transport to model variable diffusion and/or partition coefficients, and the presence of slow equilibration/slow binding kinetics within stratum corneum. The model was validated by comparing it with the diffusion model which was solved numerically using the finite element method. It was found that the new compartmental model predictions agreed well with that of the diffusion model, providing a sufficient number of compartments was used. The compartmental model was applied to two previously published experimental data sets: water penetration and desorption data and the finite dose dermal penetration of testosterone. Significant improvement of the fitting quality for all these data sets was achieved using the compartmental model.

Compartmental modeling of skin transport.

The primary objective of this study is to introduce a simple and flexible mathematical approach which models transport processes in skin using compartments. The main feature of the presented approach is that the rate constants for exchange between compartments are derived from physiologically relevant diffusional transport parameters. This allows for better physical interpretation of the rate constants, and limits the number of parameters for the compartmental model. The resulting compartmental solution is in good agreement with previously published solutions for the diffusion model of skin when ten or more compartments are used. It was found that the new compartmental model with three compartments provided a better fit of the previously publish water penetration data than the diffusion model. Two special cases for which it is difficult to implement the diffusion model were considered using our compartmental approach. In both cases the compartmental model predictions agreed well with the diffusion model.

A fiber distribution model for predicting drug release rates.

Sustained drug release can be achieved by loading a drug into polymer material. The drug release can then be controlled for potential use in various biomedical applications. A model for drug release from a polymeric fibrous scaffold, which takes into account the distribution of fiber diameters within its structure, is developed here. It is demonstrated that the fiber diameter distribution significantly affects the drug release profile from electrospun scaffolds. The developed model indicates that altering the fiber distribution can be used as an additional tool to achieve an appropriate drug release profile. Using published data, it was demonstrated that an application of the model allows a more precise calculation of the drug diffusion coefficient within the polymer, which is important for predicting drug release rates from fabricated materials.