Influence of Dose, Particle Size &Amp; Concentration on Dermal Penetration Efficacy of Curcumin

Dermal penetration is considered to mainly occur via passive diffusion. Therefore, a high concentration gradient of dissolved active ingredient between formulation and skin is needed to achieve an effective dermal penetration. The concentration gradient between formulation and skin can be changed by changing the amount of dissolved active ingredient in the formulation. In case of poorly soluble active ingredients this can be achieved by using nanosized drug material instead of larger sized material. The smaller size and the resulting larger surface increase the kinetic solubility and thus increase the concentration gradient of dissolved active ingredient between formulation and skin, which then results in an increased dermal penetration. In this study we demonstrated that the concentration gradient between formulation and skin can also be influenced by the number of particles being present in the formulation and by the dose (volume of formulation) applied to the skin. Particles of undissolved active ingredient are known to act as a reservoir by releasing dissolved molecules in the liquid phase of the formulation. It could now be demonstrated that the particles - once the liquid in which they are dispersed evaporates - can connect to the skin via an aqueous meniscus. The aqueous meniscus contains dissolved active ingredient and therefore creates a small local spot with a locally high concentration gradient and improved dermal penetration. Therefore, the dermal penetration can be increased with formulations that contain high amounts of particles. This can be achieved by applying formulations with high numbers of particles and/or by applying larger volumes of particle containing formulations to the skin.