Liposomes as an in vitro model for predicting the eye irritancy of chemicals

Liposomes containing 4-methylumbelliferyl phosphate (Um-P) were prepared using the lipid extracts from bovine eyes and were incubated with seven surface-active agents. The Um-P released from the liposomes by each test agent was hydrolysed with alkaline phosphatase and the resultant 4-methylumbelliferone was assayed spectrofluorometrically. The values for Um-P(50) (the concentration of test material at which 50% of Um-P is released) showed a good inverse correlation with the irritation scores obtained by the Draize eye test. The results suggest that the liposomal assay reported here may be useful as an in vitro model for predicting the eye irritancy of chemicals.