Supplementary Material for: Dermal Penetration Analysis of Curcumin in an ex vivo Porcine Ear Model Using Epifluorescence Microscopy and Digital Image Processing

<b><i>Introduction:</i></b> Curcumin is a promising drug candidate, but its use for dermal application is limited due to its poor aqueous solubility. Thus, formulations that increase the solubility of curcumin are needed to fully exploit the therapeutic potential of curcumin. Various previous studies address this issue, but a comparison of the efficacy between these formulations remains difficult. The reason for this is a missing standard formulation as benchmark control and an easy-to-use skin penetration model that allows for a fast discrimination between different formulations. <b><i>Objective:</i></b> Thus, the aims of this study were the development of a curcumin standard formulation and a screening tool that allows for a fast discrimination between the dermal penetration efficacies of curcumin from different formulations. <b><i>Methods:</i></b> Ethanolic curcumin solutions were selected as simple and easy to produce standard formulations, and the ex vivo porcine ear model, coupled with epifluorescence microscopy and subsequent digital image analysis, was utilized to determine the dermal penetration efficacy of curcumin from the different formulations. <b><i>Results:</i></b> Results show that the utilized skin penetration model is a suitable and versatile tool that enables not only a fast determination of the dermal penetration efficacy of curcumin from different formulations but also a detailed and mechanistic information on the fate of chemical compounds after dermal penetration. Ethanolic solutions containing 0.25% curcumin were found to be the most suitable standard formulation. <b><i>Conclusions:</i></b> Results of the study provide a new, effective screening tool for the development of dermal formulations for improved dermal delivery of curcumin.