Patent ID: 6982152

Claim:
A method for determining cytotoxicity of a test agent, the method comprising: (a) contacting living cells in culture medium contained in a vessel, with a pre-determined amount of the test agent; and (b) incubating the cells in culture medium from step (a) for a pre-determined amount of time; then (c) adding to the cells and culture medium from step (b) a reagent mixture that is non-toxic to the living cells, wherein the reagent mixture comprises: a solvent, a dye having an oxidized state and a reduced state wherein the reduced state can be distinguished from the oxidized state and wherein the dye is initially present in the oxidized state, an electron transfer agent, a substrate for a cytoplasmic enzyme having a half-life greater than two hours, and a cofactor for the cytoplasmic enzyme; and then (d) measuring the culture medium from step (c) for production of the reduced state of the dye, the production of the reduced state of the dye being caused by a cytoplasmic enzyme specific for the substrate in the reagent mixture added in step (c), wherein the cytoplasmic enzyme is released from dead and dying cells within the vessel, whereby the cytotoxicity of the test agent is determined.