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Comet assay, also known as single cell gel electrophoresis (SCG), is a microgel electrophoresis technique which detects DNA damage and repair in individual cells. The damage is represented by an increase of DNA fragments that have migrated out of the cell nucleus in the form of a characteristic streak similar to the tail of a comet. The DNA fragments are generated by DNA double strand breaks, single strand breaks and/or strand breaks induced by alkali-labile sites in the alkaline version of the assay. The length and fragment content of the tail is directly proportional to the amount of DNA damage (see fig.1).


Comet assay can be conducted in both in vitro and in vivo test systems and is increasingly being used in genotoxic testing of industrial chemicals, agrochemicals and pharmaceuticals. Comet assay is rapid (results in days), simple to perform, requires small amounts of test substance (25-50 mg) and can be performed in almost any eukaryotic cells (different animal organs). Comet assay serves as an important tool in the early drug development compounds as a mechanistic and genotoxic predictor.


Fig 1 - DNA damage of liver and stomach cells of mice 24 hours after oral gavage administration of methylmethesulfonate




In vivo Comet testing

The in vivo Comet assay is a Tier II assay that can be used to provide more detailed information when a positive test result is found in the initial FDA / ICH GLP genetic toxicology tests. It is the only Tier II assay that can perform genotoxicity testing at the organ tissue level across a range of organ types. These include: lung, liver, stomach, bone marrow, bladder, kidney, skin & eye.

New - In vitro Comet testing

BioReliance can now offer an in vitro Comet assay. This provides all the advantages of the Comet test but can be performed earlier in the drug development process and help prioritize which compounds to take further into development, thus offering considerable savings in time and money. At BioReliance, in vitro Comet can assess DNA damage in any cell line. The assay can also be used to complement the information gained through the ICH Gene Tox battery of tests and be part of the submission package to regulatory agencies.

COMET Assay/DNA Damage Assay