NEW EPIDERMAL MODEL FOR DERMAL IRRITANCY TESTING.

A model of the human epidermis, EpiDerm™, based on neonatal, foreskin-derived normal human epidermal keratinocytes (NHEK) has been developed over the past 18 months at MatTek Corporation. Cultured in easily handled Millicell® CM (Millipore Corp.) cell culture inserts, the model allows application of liquid and solid test materials (potential dermal irritants) directly to the stratum corneum of this air-lifted, highly differentiated culture. An interlaboratory comparison, which tested 16 anionic and non-ionic surfactants and surfactant-containing final formulations, utilized the MTT assay with both concentration (EC-50) and time protocols (ET-50). The 16 compounds were tested on different production lots of EpiDerm following 1 and 2 day storage periods (post-shipping) at MatTek and at an independent contract testing laboratory. The EC-50’s and ET-50’s from the 2 laboratories were plotted against one another and least squares fit to the Y=X. The resultant correlation coefficient, r, for the EC-50 data was 0.970; for the ET-50 data, r=0.989. Correlation of these in vitro results to human clinical chamber irritation and repeat handwash testing gave correlations with r values ranging from 0.977 to 0.993. Thus, the EpiDerm model appears to have utility in predicting clinically observed dermal irritation in vitro.