A team of MIT and Harvard researchers has developed a new way to screen cells for signs of DNA damage. The hope is that this new technology may become quite popular for testing the effectiveness of cancer drugs or for identifying environmental or metabolic factors responsible for genetic damage. The technique is an advancement on the “comet assay”, also known as Single Cell Gel Electrophoresis assay.
Some details from MIT:
The comet assay is based on gel electrophoresis, a commonly used lab test in which an electric field is applied to DNA placed on a slab of polymer gel, forcing the DNA to move across the gel. During electrophoresis, damaged DNA travels farther than undamaged DNA, producing a comet-shaped smear. (The damaged DNA forms the “tail” of the comet.)
This test is generally considered very sensitive, but is also quite laborious. Each experimental condition (for example, a test of how a particular drug affects DNA) requires its own microscope slide, and each slide (containing hundreds of cells) must be visually inspected by the researcher. This limits the number of experimental conditions that can be studied.
To create the new test platform, the researchers from the Bhatia and Engelward laboratories developed the concept of microwells printed into the electrophoresis gel. Using a micropatterning technique developed by Wood and Bhatia, a grid of thousands of tiny indentations is created on the gel. Each cell is placed in its own indentation, giving it an “address” that stays constant throughout the process. Furthermore, each gel can be subdivided into distinct environments by placing a 96-well plate over the gel. Each well confines about a thousand cells, allowing the researchers to add different drugs or other chemicals to each well to compare their effects on DNA damage and repair.
This setup allows dozens of experimental conditions to be tested on just one slide, and it enables slides to be automatically analyzed using custom-designed imaging software.
To demonstrate the potential usefulness of the new system, the researchers evaluated three compounds that have been proposed as potential inhibitors of DNA repair. Such compounds could be used to boost the effectiveness of chemotherapy agents by preventing cancer cells from repairing the DNA damage caused by chemotherapy. Their study supported earlier predictions that two of the compounds, known as myricetin and DOPA, appear to halt DNA repair, while a third, called NCA, has little effect.