Effect of fractal dimension on drug permeation through porous ethylcellulose films.
Fractal geometry was applied to quantify the complexity of an internal structure of a porous film prepared with ethylcellulose (EC) and diethylphthalate (DEP) as a plasticizer. EC was dissolved together with DEP in a water-ethanol mixture solution, and then evaporated on Teflon petri dishes in order to make porous EC films. Boundary lines of the porous structures in the EC film cross section were taken by a confocal laser microscope as image data, and these images were fed into a computer to estimate the fractal dimension. The porous structure in EC film was observed to be a typical fractal and its complexity was quantified as a non-integral fractal dimension. No clear correlation was observed between the fractal dimension and the porosity of EC films, suggesting that they were mutually independent parameters representing the porous structure in the EC films. The permeation of theophylline through the EC films was determined by using two-chamber diffusion cells. A fairly good relationship between the permeability coefficient of theophylline and the fractal dimensions was observed, suggesting the usefulness of the fractal dimension as a novel parameter for evaluating drug permeation through porous films.
Department of Pharmaceutics, Hoshi University, Tokyo, Japan.
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Yamane
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Takayama
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Nagai
D002482:Cellulose / Q000008:administration & dosage / Q000031:analogs & derivatives*; D016503:Drug Delivery Systems; D010539:Permeability
C013517:ethyl cellulose; D002482:Cellulose