There remains a risk of toxicological reactions due to systemic absorption and photo-instability of sunscreens. The present study investigated the safety profile (cytotoxicity, phototoxicity, photostability, UV filter release profile and skin irritation properties) of sunscreen (NLC-TRF sunscreen) produced from nanostructured lipid carriers (NLCs) and a tocotrienol-rich fraction (TRF). It evaluated the cytotoxicity and phototoxicity of the sunscreen on normal human dermal fibroblast (NHDF) and tested skin irritation properties on the skin model. Besides, it analyzed the photoprotection in pre- and post-UV irradiation to determine the photostability. Additionally, it also evaluated the release profile for UV filters (diethylamino hydroxybenzoyl hexyl benzoate [DHHB] and ethylhexyl triazone [EHT]). 

• The NLC-TRF sunscreen showed no cytotoxicity and skin irritation to provoke cell death.
• It demonstrated no phototoxic effect and high photostability up to 10 minimal erythema dose (MED) to confirm a high sun protection factor (SPF) value above 50 and broad-spectrum UV absorption.
• The NLC-TRF sunscreen indicates its safety for topical application with a sustainable release profile for UV filter (cumulative release of 28% for DHHB and 40% for EHT after 8 h) due to the application of NLCs. 

This study suggests that the NLC-TRF sunscreen is an advanced formulation that features improved stability and is safe for topical delivery.

Source: Chu CC, Hasan ZAA, Tan CP, et al. In vitro safety evaluation of sunscreen formulation from nanostructured lipid carriers using human cells and skin model. Toxicol In Vitro. 2022;84:105431.