In vitro eye irritation studies on organosilicon compounds

The development of alternatives to in vivo eye irritation testing in animals is spurred by humane, scientific, and economic considerations. Two commercially available in vitro assays (Epi-Ocular Tissue Model OCL-100 and Skin(2) ZK-1200 model) and a third published assay, the Bovine Corneal Opacity and Permeability Assay (BCOP), were used to assess the eye irritancy potential of several organosilicon (OS) compounds to evaluate their suitability for testing silicone polymers and other materials. The Skin(2) ZK-1200 model (nine OS compounds) was generally applicable for the in vitro assessment of eye irritancy of liquid silicone polymers. However, some effort will be required to overcome the problem of working with viscous pastes and volatile low surface tension test materials for which variable results were observed. The correlation of the Skin(2) model in vitro eye irritancy results with known in vivo data was generally good for silicone polymers, although some alkoxysilanes do not appear to give in vitro results that correspond with their in vivo irritancy. In vitro results obtained with the Epi-Ocular Tissue model OCL-100 (although limited) correctly identified both irritant and nonirritant silicone polymers. The BCOP assay correctly identified four nonirritant (two polydimethylsiloxanes, one phenylsilsesquioxane, and one silicone polyether) and two irritant (aminofunctional siloxane) polymers that are used extensively in personal care formulations. Histologic examination of the treated corneas yielded results that correlated well with the opacity and permeability endpoints. All three models performed well and are worthy of future study with OS compounds. Of the two tissue construct models, the Epi-Ocular Tissue model OCL-100 had several advantages over the Skin(2) ZK-1200 model: it appeared to have a better technical design, facilitating more reliable dosing of the test materials and ease of use.