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Peer-Reviewed Publication

Modeling the antioxidant properties of the eye reduces the false-positive rate of a nonanimal eye irritation test (OptiSafe)

Toxicology In Vitro, Vol. 76, October 2021 · Lebrun Labs Research Team

Overview

The living eye is not a passive target, it actively defends itself against chemical insults through a rich antioxidant system in the tear film and aqueous humor. This paper describes how Lebrun Labs incorporated that biological reality into the OptiSafe™ test design, using a biomimetic antioxidant model to filter out false-positive signals generated by chemicals that are reactive in a test tube but harmless to an actual eye. The approach is grounded in the mechanistic biology of ocular defense and represents a significant step toward making in vitro eye irritation testing as accurate as possible without using animals.

Abstract

Nonanimal eye irritation tests based on macromolecular substrates are susceptible to false-positive results when tested chemicals react with the substrate through oxidative or reductive mechanisms that do not reflect genuine ocular irritation. The eye's tear film and aqueous humor contain significant concentrations of antioxidants, including ascorbic acid, glutathione, and uric acid, that neutralize reactive species before they can damage ocular tissue. This study developed a biomimetic antioxidant model that incorporates these protective components into the OptiSafe™ assay protocol. The model was evaluated against a reference chemical set containing both confirmed irritants and reactive nonirritants. Incorporation of the antioxidant model significantly reduced the false-positive rate compared to the unmodified assay, while sensitivity for true GHS Category 1 and Category 2 irritants was maintained. The findings support the biological plausibility of the approach and provide a mechanistic rationale for the observed improvement in specificity.

Relevance to Lebrun Labs Services

This publication underpins the scientific rationale for the antioxidant-supplemented OptiSafe™ protocol that Lebrun Labs uses in its contract testing program. Clients submitting eye irritation data for cosmetic safety assessments, GHS classification, or EU CLP compliance benefit directly from this research, it means the test results they receive are less likely to overclassify a safe ingredient as an eye irritant. This is especially important for formulators working with vitamin C derivatives, botanical extracts, and other antioxidant-rich ingredients that might otherwise trigger false positives in older test formats. Our scientific team can discuss how the current OptiSafe™ protocol applies to your specific formulation chemistry.

Research reported in this publication was supported by the National Institute of Environmental Health Sciences of the National Institutes of Health under Award Number SB1ES025501. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.