DNA-comet Assay

DNA-comet assay is a sensitive and rapid biological technique with low cost for the identification of irradiated foods through the detection of DNA damage in foodstuffs caused by irradiation. DNA-comet assay provides advantages including convenience and simplicity as a method for food irradiation testing. It is a qualitative and quantitative method to some extent for the irradiation detection of a variety types of foods. It can detect foodstuffs that even have been exposed to low doses of radiation.

Figure 1. Gel electrophoresis unit for DNA-comet assay in food irradiation testing

Most foodstuffs contain DNA. The DNA molecule in the foodstuffs is a sensitive target to ionizing radiation due to their large size. This is also one of the reasons that radiation can be used to kill microorganism, parasites and insects effectively in foods for sterilization and shelf-life extension. The irradiation can lead to the fragmentation of DNA by single or double strand breaks. Additionally, the DNA helix and cross-linking can be denaturized, and base modifications can occur in the foods after irradiation treatment. The changes in DNA caused by irradiation can be a basis and used as a biological marker to detect radiation treatment. DNA-comet assay can be applied in the qualitative and quantitative measurement of DNA damage in a single cell.

DNA-comet assay is a microgel electrophoresis of single cells that is used to detect DNA fragmentation. The principle is based on the migration of DNA out of the cell in the direction of anode, showing like "comet". The extent of DNA damage is related to the shape and size of a Comet as well as the distribution of DNA within the Comet. After the radiation treatment applied on the foodstuffs, the fragmented DNA is stretched by the electrophoresis of irradiated cells. The irradiated cells are stained as Comets with tails and the non-irradiated cells remain intact and appear as Comets without tail. The DNA of most non-irradiated food samples have intact structures, while the irradiated foods demonstrate different degrees of DNA damage from varying irradiation doses. Therefore, the irradiated foods can show significant and obvious differences from non-irradiated foods.

Many regulatory studies have increasingly recognized DNA-comet assay as a valuable tool for food irradiation testing. Although this technique is not specific to radiation, it is still very useful for rapid and inexpensive preliminary screening of irradiated foods. A confirmation of positive results is recommended using a standardized method to specifically prove an irradiation treatment of the food sample. It can be employed for onsite applications for the compliance of labeling regulations. DNA-comet assay has been adopted by the European Committee for Standardization as a standard method for the rapid screening of irradiated foods which contain DNA.

The procedure for the food irradiation testing using DNA-comet assay includes sample preparation and pretreatment, cell suspension preparation, and detection using gel electrophoresis. We have expertise in the sample preparation of a variety types of foodstuffs. The sample preparation has a significant effect on the accuracy of the level measured in the food samples.

We offer an accurate and validated DNA-comet assay platform for the identification and detection that have been widely applied in the food irradiation testing to meet customers' needs. We also maintain high quality assurance for the food irradiation analysis.