Ocular tolerance - Neutral red release
Neutral red release
Alternative method for evaluating a cytotoxic potential and studying the ocular tolerance of a product
The neutral red release assay is an official assay in France for the testing of cosmetic formulations. https://www.legifrance.gouv.fr/jorf/id/JORFTEXT000000398193.
That assay was first published in 1992 by scientists at Biopredic International (DOI : 10.1007/BF00755785) before multi laboratory studies and final publication in the JORF in 1999.
The protocol is quite unique in 2 aspects: the incubation time is very short -1 minute - compared to classical cytotoxicity assays where a 24 h exposure time is common. The test product is applied directly onto the cell monolayer, instead of being diluted in the culture medium and it is applied as such or with limited dilutions. The assay reflects the alteration of the cell membrane by the surfactants and other ingredients of the formulation; this alteration provokes the release of the dye previously incorporated into the cells. The membrane alteration is one of the mechanisms involved in eye irritation in vivo.
Assay completed in: 5 weeks.