HYDRATION EFFECT ON HUMAN NAIL PERMEABILITY
It has been long known that hydration strongly affects transport and mechanical properties of keratinized membranes. The most studied keratin structures are human stratum corneum, wool and hair. The effect of hydration on transport, however, has not been studied in human nails. This investigation is aimed at filling this gap. In the first phase of the work we have determined the equilibrium water sorption isotherm for human nail. The isotherm obtained in our laboratory was compared with available literature data for nail and other keratinized tissues. Results were described in terms of theoretical sorption models used in natural polymers and food systems including Guggenheim-Anderson-de Boer and D’Arcy-Watt isotherms. Of the models tested, D’Arcy-Watt gave the best description over the entire range of hydration. We further investigated transport properties in nail of water and the antifungal drug, ketoconazole as a function of nail hydration which was controlled by adjusting the relative humidity on one or both sides of the tissue. Diffusivity of water in nail was studied using both vapor phase and liquid phase sorption-desorption techniques. The values obtained ranged from D = 3.160 × 10-7 cm2/s at a water volume fraction phi1 = 0.4107 to D = 7.68 × 10-10 cm2/s at phi1 = 0.0431. They are interpreted in terms of a free volume theory. Transport parameters of ketoconazole were obtained by conducting permeation experiments using a single chamber diffusion cell designed specifically for nail permeation studies. Flux of ketoconazole solvent-deposited onto the nail from ethanol increased consistently with an increase in water content in the nail. Diffusivities estimated from these data can be described by Fujita theory. The findings show that hydration provides enormous increases in water transport through nail, but only a modest (2-3 fold) increase in ketoconazole permeation under conditions attainable in vivo. Thus, nail penetration enhancement by hydration is not large enough for it to be considered as the only factor in formulating a more effective topical treatment of nail disorders. The effect of hydration on diseased nail permeability remains to be evaluated.
School:University of Cincinnati
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:nail keratin permeability hydration water
Date of Publication:01/01/2006