Evaluation of different setups for the measurement of drug penetration into the nail

Topical therapy of onychomycosis, a fungal infection of nail plate and/or nail bed, offers an attractive alternative to treatment with systemic antifungals. To treat fungal infections locally, antifungal-loaded nail lacquers have been prepared in our laboratory. Franz diffusion cells have been used to investigate drug permeation from such lacquers into and through the nail plate in vitro. Although Franz diffusion cell is convenient for permeation study, it does not mimic the physiological fungal-infected nail bed conditions for evaluating antifungal effectiveness. Alternative setups to the Franz diffusion cells have been investigated, where the nail plate is placed on a wet cotton ball [1] or on agar gel, the wet cotton ball and agar gel being equivalent to the receptor compartment of Franz diffusion cells, and the drugloaded vehicle is applied to the surface of the nail plate. Such a setup can allow the permeation of antifungal drugs to be tested directly, for example, if the agar gel is seeded with fungi, drug permeation through nail plate and into agar gel could be measured as a fungi-free clearance zone to be directly related to drug penetration into and through the nail plate [2].