Cytotoxicity of lecithin-based nanoemulsions on human skin cells and ex vivo skin permeation: Comparison to conventional surfactant types

As constituents of cellular membranes, lecithins feature high biocompatibility and great emulsifying properties due to their amphiphilicity. Additionally, there are expectations that these naturally occurring emulsifying agents can replace other skin damaging emulsifiers like sodium dodecyl sulfate or sodium laureth sulfate. However, cytotoxicity data of lecithin-based formulations on primary human skin cells are scarce. Thus, we developed nanoemulsions with different kinds of surfactants (amphoteric, anionic and non-ionic), studied the skin permeation of a model drug from this formulations employing Franz-type diffusion cells and monitored their cytotoxicity potential on primary human keratinocytes and fibroblasts using a cell proliferation assay. The skin diffusion studies demonstrated that the amphoteric lecithin-based emulsifiers were superior to non-ionic surfactants in terms of skin permeation, but inferior to anionic emulsifiers. Further, we found that the nanoemulsions containing the amphoteric lecithins as emulsifying agents lead to significantly higher viability rates of both epidermal keratinocytes and dermal fibroblasts than the investigated anionic and non-ionic surfactants. This renders them a promising alternative to conventional emulsifiers used in daily products.