Modified EpiDerm Skin Irritation Test for Hazard Identification and Labelling of Chemicals According to EU Classification System

The Modified EpiDerm SIT is an in vitro method that has been developed and optimized to predict the skin irritation potential of chemicals according to EU classification system. The method utilizes a commercially available three-dimensional tissue construct EpiDermTM (EPI-200) produced by MatTek Corporation (US).

The test consists of a topical exposure of the neat test article to a human reconstituted epidermis model for 60 min. During the 60 minute exposure period, the treated epidermis is first left at room temperature for 25 minutes and subsequently incubated for 35 min at 37°C. At the end of exposure, the test article is removed from the epidermis and the tissue is incubated for an additional 42h to express the resulting damage. Cell viability is measured by dehydrogenase conversion of MTT [(3-4,5-dimethyl thiazole 2-yl) 2,5-diphenyltetrazoliumbromide], taken up by cell mitochondria, into a blue formazan salt that is quantitatively measured after extraction from tissues. Relative tissue viability is determined against the concurrent negative control-treated tissues.

Tissues treated with skin irritants (R38) are expected to show a relative viability of less than 50% while non-irritants show a viability greater than 50%. A concurrent positive control is used with each assay.

The modified EpiDerm SIT has been adopted together with EpiSkinTM (SM), SkinEthic™ RHE, LabCyte EPI-MODEL24 SIT test methods, and included in OECD TG 439 which describes an in vitro procedure that may be used for the hazard identification of irritant chemicals (substances and mixtures) in accordance with the UN Globally Harmonized System of Classification and Labelling (GHS) Category 2.