The combination of iontophoresis with solid lipid nanoparticles (SLNs) for targeting drug delivery to the epidermis has not been explored. The goal of this paper was to study the influence of iontophoresis on the penetration of doxorubicin (DOX) delivered in SLNs (DOX-SLNs). We measured the contribution of electroosmotic flow to the transport of DOX, and the accumulation of DOX in the stratum corneum (SC) and in the viable epidermis was determined. In addition, we evaluated the cytotoxicity of DOX-SLNs against skin cancer cells. Iontophoresis of unloaded SLNs decreased the electroosmotic flow by a factor of 5 and increased the skin resistance. Nevertheless, iontophoresis of DOX-SLNs increased DOX delivery to the viable epidermis, with 56% of all DOX penetrating this skin layer. Only 26% of the drug was retained in the SC. In contrast, passive delivery retained 43% of DOX in the SC and 26% in the viable epidermis. DOX-SLNs increased DOX cytotoxicity against melanoma cells by 50%. These results suggest the use of DOX-SLN iontophoresis in the topical treatment of skin cancer.

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Nitric oxide (NO) is a gaseous molecule that has specific functions dictated by its localization and its kinetics of release. As NO-donors have a range of potential uses in the skin, much attention has been paid to the development of topical NO delivery systems. The aim of this work was to study the release rate and the skin penetration of the NO-donor cis-[Ru(NO(2))(bpy)(2)(4-pic)](+) from different gel formulations and their potential as topical NO delivery systems under light stimuli. Among the formulations developed, the anionic gel retarded the nitro-ruthenium complex diffusion and also obstructed NO release after light irradiation. On the other hand, NO release before light irradiation was observed when the complex was dispersed in the cationic chitosan gel, possibly due to oxi-redox reactions between the amino groups of the polymer and the drug molecule. Finally, the non-ionic gel released the NO after light irradiation to the same extent as a drug aqueous solution at the same pH. The drug dispersed in this gel also penetrated into the stratum corneum skin layer, and the nitro-ruthenium complex present in the skin was able to release the NO after light stimuli, suggesting the potential use of this formulation as a topical NO delivery system.

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