Thesis title: "Phospholipid-based emulsifiers for sunscreen development: impact of UVA and effect on skin properties in vitro, ex vivo and in vivo"

Thesis outline: Phospholipids are known for their high biocompatibility, which renders them interesting candidates for dermal formulations. Since phospholipid derivatives lack groups with distinct photoactivity, we hypothesize that they could be used as emulsifiers for sunscreen emulsions. Ingredients of sunscreen products need to feature excellent biocompatibility and should not cause phototoxic reactions since the skin is subjected to prolonged photo-stress. The goal of our research is to evaluate the behaviour of phospholipid-based emulsifiers in aqueous dispersions and oil-in-water emulsions under UVA irradiation in comparison to conventional surfactants.

Phototoxicity tests on primary human keratinocytes and fibroblasts will be conducted to compare the cytotoxicity of different surfactants when tested in presence and absence of simulated solar light. We will also perform diffusion cell studies to evaluate whether treatment of skin with the different test formulations and UVA light will affect skin penetration. The experiments will be conducted on the porcine ear model. In addition, we will test important skin parameters to evaluate the effects of the different surfactants and UVA light on skin. We will measure transepidermal water loss, stratum corneum hydration, pH and erythema value. Confocal Raman spectroscopy will allow us to measure urea, natural moisturizing factor and hydration in different skin depths. These tests will be performed on porcine ear skin as well as healthy human volunteers to identify the impact of the tested formulations in combination with photo-stress.

Funding: This project is funded by the Phospholipid Research Center, Heidelberg, Germany (VKL-2022-099/1-1).

Supervisor & Co-Mentor: Lea Ann Dailey, Victoria Klang