Earl, L.K., Hall-Manning, T.J., Holland, G.H., Irwin, A., McPherson, J.P., Southee, J.A. Unilever Research, Colworth House, Sharnbrrok, Bedford , UK, Microbiological Associates Ltd, Stirling University, Innovation Park, Stirling, UK.

Simple in vitro cell culture methods are often inappropriate for investigating the cytotoxicity of high concentration test substances. The relevance of these assays for assessing skin irritation potential substances such as surfactants or surfactant mixtures, where the toxicity of the substance is related to its physicochemical state which is in turn dependent on its concentration, is questionable. The present study compares data generated in vivo with data obtained from two in vitro assays which allow direct application of the test substance: the agarose overlay cytotoxicity assay, and an MTT time-course on a 3D human skin model (EpiDerm™). A range of surfactants and combinations of surfactants was tested on human volunteers in a 4-hour skin covered patch test. The results show that equal mixtures of sodium dodecyl sulphate (SDS) and N,N-dimethyl-N-dodecylaminobetaine (DDB) have reduced skin irritation potential compared with their single applications at the same concentrations. The results of the agarose overlay assay did not distinguish between any of the treatments, suggesting that the assay requires careful development in order to distinguish between these concentrated materials. The results of the EpiDerm time-course, however, broadly reflect the results seen in vivo and indicate that it is possible to distinguish between different surfactants and their mixtures in vitro. Moreover, simple binary mixtures of surfactants at equal concentrations have markedly reduced cytotoxicity potential. The results of this study indicate that 3D skin models may have practical applications in testing skin irritation potential of concentrated surfactant systems.


Cutaneous irritancy, Cutaneous irritation, Cutaneous toxicity, Cytotoxicity, Dermal irritancy, Dermal irritancy testing, Dermal irritation, Endpoints, MTT, EpiDerm, MTT, MTT ET-50 tissue viability assay, MTT assay, Skin irritancy, Skin irritation, Skin models, cultured, Sodium dodecyl sulfate (SDS), Surfactants, Surfactants, cytotoxicity potential of mixtures, Surfactants, irritancy/irritancy potential

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