Safety and efficacy assessment of photoprotective formulations containing quercetin in nanostructured lipid carriers (CLN-QT)

Author(s)

Camila Martins Kawakami

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Ciências Farmacêuticas de Ribeirão Preto (PCARP/BC)
• Defense date: 2019-12-12

Examining board members

Lorena Rigo Gaspar Cordeiro; Daniel Junqueira Dorta; Marize Campos Valadares

• Advisor: Lorena Rigo Gaspar Cordeiro

Abstract

Nowadays it is well known that the regular application of UV filters is one of the main strategies in the prevention of damage induced by ultraviolet radiation (UV). However, the use of photounstable combinations can reduce photoprotective efficacy and lead to the formation of reactive intermediates, which may have potential to cause photoirritation, photoallergy and photogenotoxicity on the skin. In addition, there has been a tendency to combine antioxidants to conventional UV filters in order to prevent oxidative damage mediated by reactive oxygen species (ROS) and quercetin (QT) is an interesting option. However, its limited cutaneous absorption can lead to a lack of photoprotective efficacy, which leads to necessity of the use of delivery systems in order to improve its penetration into the skin. Therefore, this study aimed to evaluate safety and efficacy of photoprotective formulations containing quercetin in nanostructured lipid carriers (CLN-QT) in cell culture, reconstructed skin model and humans. Firstly, four photoprotective formulations (F1, F2, F3 and F4), containing different combinations of diethylamino hydroxybenzoyl hexyl benzoate (DHHB), ethylhexyl methoxycinnamate (MTX), avobenzone (AVO) and bemotrizinol (BMTZ) were submitted to the studies of photostability, photoreactivity, ROS generation (using DCFH2-DA probe), phototoxicity in 3T3 fibroblast culture and photogenotoxicity by comet assay. The combination C2 (containing DHHB and MTX) presented better results regarding photostability and photoreactivity when compared to combinations C1 (containing MTX and AVO) and C3 (containing MTX, AVO and 3% BMTZ), so it was combined to CLN-QT and subsequent studies were performed. Moreover, combination C2 did not increase intracellular ROS levels after UVA irradiation and it was not considered phototoxic. In the present study, it was observed that the inclusion of complementary biological assays to the photostability study provided more relevant results when compared to the photostability as a stand-alone assay for the selection of the best combination. In addition, it was demonstrated a good correlation between intracellular ROS production and photoreactivity, so we suggest the inclusion of intracellular ROS production in the photostability evaluation strategy. The safety and efficacy results demonstrated that UV filters + CLN-QT did not present cytotoxicity in primary human keratinocytes and were not considered phototoxic in reconstructed skin model. The CLN-QT + UV filters did not alter SPF (sun protection factor) in humans (protection against erythema), however they reduced intracellular ROS generation after UVA irradiation (about 30%), when compared to UV filters alone and thus complemented the efficacy of photoprotective formulations. (AU)

• FAPESP's process: 15/10017-3 - Efficacy and safety assessment of photoprotective formulations in reconstructed human skin: effect of photostability on markers related to photoaging and skin cancer
• Grantee: Camila Martins Kawakami
• Support Opportunities: Scholarships in Brazil - Doctorate