ABSTRACT
Assessment of ocular and dermal toxicity is a standard practice for many types of consumer and industrial formulations and individual chemicals. The development of in vitro assays to predict ocular and dermal toxicity has proved to be challenging. Even though the in vivo exposures are topical, the exposure kinetics may be quite complex.2 Therefore, topical application to tissues (natural or reconstructed) in vitro has proved to be the most useful method of testing broad classes of chemicals. Select monolayer cell culture systems have proved valuable for predicting the ocular irritation potential of aqueous-soluble chemicals and product classes, provided that their irritancy potential was not rapidly quenched by aqueous dilution. For example, products containing surfactants may be readily tested in these culture medium-based assays, since surfactants retain their inherent activity in an aqueous environment.3 In contrast, products containing ethanol or acetone may be notably underestimated in these assays since the cytotoxic effects of these small solvents are rapidly diluted to extinction in the
Introduction to In Vitro Toxicology........................................................................................................................................... 197 Assessment of Ocular Irritation Potential ................................................................................................................................. 204 Assessment of Dermal Irritation Potential.................................................................................................................................214 References................................................................................................................................................................................. 227
classes are not amenable to these simpler systems because some of the actives in the formulation may be hydrophobic and thus not adequately bioavailable to the test system. Accordingly, these products should ideally be tested in a tissue-based assay system where the undiluted formulations can be presented to the test system in the same manner as occurs in vivo and the effects of the actives appropriately evaluated.5,6 These tissues may be short-term ex vivo organ cultures or engineered tissue constructs. Complex exposure kinetics, such as dermal penetration and subsequent action of topically applied formulations, require the use of complex systems that can model both the barrier properties of skin and provide the necessary target cells.7
