3T3 NRU- OECD 432

The 3T3 Neutral Red Uptake (NRU) Phototoxicity Test is approved by the Organization for Economic Cooperation and Development (OECD). It is used to detect the viability of Balb/c 3T3 cells (mouse fibroblast cell line) after exposure to a chemical and subsequent exposure to UVA light. Phototoxicity is measured as an inhibition of the capacity of the cells to take up the NR, one day after treatment with the chemical using the NRU assay principles.

Human 3-D skin model

Epidermal skin models, such as EST1000, closely resemble the cellular structure of natural human epidermis showing a basement membrane, proliferating keratinocytes and stratum corneum with an intact barrier function. They allow for topical application of compounds providing a more physiological test system, in contrast to the 3T3 NRU system which is limited to soluble compounds as well as species differences. Chemicals may be applied to the surface of the skin model, subsequently exposed to UVA light and in turn metabolic activity of the cells determined using the MTT assay.