PREDICTION OF EYE IRRITANCY POTENTIAL OF SURFACTANTS BY CYTOTOXICITY TESTS INVITRO ON CULTURES OF HUMAN SKIN FIBROBLASTS AND KERATINOCYTES

The cytotoxicity of surfactants was evaluated on cultures of human skin fibroblasts and keratinocytes in order to predict their eye irritancy potential taking into account both immediate cytotoxicity after 2 hr of incubation and delayed cytotoxicity 24 hr after such incubation. The immediate cytotoxicity ranking of the surfactants, evaluated by MTT or neutral red assay after 2 hr of exposure in minimum Eagle's medium (MEM) without or with 10% foetal calf serum (FCS), was identical for both cell types. Keratinocytes were less sensitive than fibroblasts to all surfactants apart from Tween; however, cytotoxicity ranking remained the same for both cell types. The addition of 10% FCS to MEM reduced the cytotoxicity of surfactants, without modifying the ranking. Comparison of immediate and delayed cytotoxicity enabled the reversibility of cellular functions to be assessed by calculation of cell recovery rate (CRR). CRR values were positively related to cytotoxicity ranking for all surfactants except Brij. No correlation was found between EC50 values of immediate or delayed cytotoxicity, under various experimental conditions, and ocular irritation scores in vivo. Brij surfactants, reported not to be irritant in vivo, showed a high degree of toxicity in the cell culture systems; however, a good correlation was found when analysis was carried out excluding these surfactants. In contrast, there was excellent correlation between CRR and ocular irritation scores in vivo, for all surfactants tested, including Brij.