The MEM elution assay or elution test is an in vitro cytotoxicity assay designed to show the presence of toxic material eluted from a test sample as it affects L929 cells cultured in the presence of the extract.

Extracts of test articles are applied to L929 cells.  After treatment, the cells are exposed to neutral red dye to differentiate between the viable and stressed or lysed cells.  The degree of irritancy is determined microscopically in the percentage of cells deformed and lysed after exposure to the test material. IIVS offers the United States Pharmacopoeia (USP) and International Organization for Standardization 10993 compliant Elution Test. The characteristics of the particular medical device, polymer, container, etc. determine the extraction procedure and the dosing method. Users of the assay include consumer products and cosmetic companies with products defined as medical devices.

Reactivity Grade

Grade Reactivity Conditions of all Cultures
0 None Discrete intracytoplasmic granules; no cell lysis, no reduction of cell growth
1 Slight Not more than 20% of the cells are round, loosely attached, and without intracytoplasmic granules, or show changes in morphology; occasional lysed cells are present; only slight growth inhibition observable.
2 Mild Not more than 50% of the cells are round and devoid of intracytoplasmic granules, no extensive cell lysis; not more than 50% growth inhibition observable.
3 Moderate Not more than 70% of the cell layers contain rounded cells or are lysed; cell layers not compleely destroyed, but more than 50% growth inhibition observable.
4 Severe Nearly complete or complete destruction of the cell layers.

Assays of Interest