Evaluation of predictable irritative power of surfactant mixtures by human fibroblast culture and its correlation to physico-chemical parameters.

Summary The predictable toxic effects of some surfactants, their blends and some preserving agents on human fibroblast cultures were investigated with in vitro tests, with the aim of finding a possible correlation between the biologic evaluations and some physical characteristics of detergent solutions. Lactate dehydrogenase release into the medium was used as a marker of the plasma membrane integrity, while the amount of 3H-radiolabelled proteins in the fibroblasts was measured in order to assess the cell biosynthetic machinery function. Disodium-alkyl-semi-sulphosuccinate induced membrane damage in the lactate dehydrogenase test and decreased the protein synthesis, with an EC 50 around 1mm, while sodium lauryl ether sulphate had an EC 50 at about 100 μm, indicating that this compound is ten-fold more toxic, when measured by this method. An ethoxylated glyceride, on the contrary, was completely harmless on the plasma membrane and, surprisingly, activated fibroblast protein synthesis in a dose-response way up to two-fold. Mixtures of the three surfactants evidenced the protective effect of the non-ionic against the cellular functionality damage. Parabens do not influence this type of evaluation, while some influence was shown by the formaldehyde releaser 2-bromo-2-nitro-propandiol at the highest concentration. The comparison between critical micellar concentration measures of the different surfactants and their in vitro detected irritative power shows, for the two anionics, that in vitro toxicity is proportionally bound to the amount of micelles even if the structural differences between the two types of molecules are reflected into different damage values, while the non-ionic compound shows a not defined CMC and a very low toxicity profile. Blends of anionics with the non-ionic show an increased CMC and a reduced toxicity profile. Toxicity evaluations of complex finished foaming formulations, carried out with human fibroblast cultures evaluation show that a relationship between micelles amount and cell toxicity seems to exist, mainly when multiple surfactants blends are tested. Resume Les effets toxiques previsibles de tensio-actifs, de leurs melanges et d'agents conservateurs sur des cultures de fibroplastes humains ont eteetudies in-vitro, dans le but de trouver une correlation entre les parametres biologiques et les caracteristiques physiques des solutions detergentes. La secretion de lactate dehydrogenase (LDH) dans le milieu a servi d'indicateur d'integrite de la membrane plasmique, et le taux de proteines marquees 3H dans les fibroplastes a ete mesure pour evaluer le fonctionnement biosynthetique de la cellule.