The Number of Ethylene Oxide Groups of Sulphate-Based Surfactants Influences the Cytotoxicity of Mixed Micelles to an Amphibian Cell Line

Abstract

Sodium lauryl ether sulphate (SLEnS) is an anionic surfactant that is widely used in many fields, such as cosmetics and detergents, among others. This study evaluated the influence of the number of ethylene oxide (EO) units, present in the head group of SLEnS, on its cytotoxicity to the A6 cell line of Xenopus laevis using MTT and resazurin assays. The A6 cell line was exposed for 48 h to six SLEnS variants: SLE0S, SLE1S, SLE4S, SLE11S, SLE30S, and SLE50S (subscript values correspond to the number of EO units). Overall, the six variants impaired the A6 cells’ viability at low concentrations for the MTT assay, with the median lethal concentrations (LC50,48h) ranging between 0.398 and 0.554 mg/L and for the resazurin assay between 0.557 and 0.969 mg/L. Further, the obtained results indicate SLEnS variants with fewer EO units to be the most cytotoxic in the resazurin assay; although a similar cytotoxicity pattern was observed with the MTT assay, a significant association between the number of EO units and the values of LC50 was not found. This result highlights the usefulness of in vitro assays with A6 cell lines as a first screening tool for assessing the structure–toxicity relationship of this type of surfactant, also providing a baseline for the development of environmentally friendlier chemical compounds while still maintaining their efficiency.