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Aug 20, 2012

DNA Biosensor Diagnostics Go with the Electron Flow

  • Scientists are hoping to exploit the electrical properties of DNA as the foundation for nanoscale biosensors capable of detecting disease-causing DNA damage or mutations. Work by the California Institute of Technology’s Jacqueline Barton, Ph.D., suggests that cells naturally use the electrical conductance properties of double-stranded DNA to signal to repair proteins in the event of damage, and that this could be turned into a diagnostic platform.

    It has long been recognized that the double-stranded helical structure of DNA is similar to that of solid-state materials used in transistors and other electrical components. The bases in a DNA ‘wire’ are essentially stacked on top of each other, and could thus feasibly be capable of conducting electricity. The flow of electrons from one end of a DNA molecule to another has now been demonstrated by Dr. Barton’s team, and although this electrical conductance was effected along a stretch of DNA that was just 34 nanometers long, such tiny lengths of DNA could be ideal as the basis for diagnostic sensors capable of detecting disease-causing DNA damage or mutations.

    Dr. Barton likens the arrangement of bases in DNA to a stack of copper pennies. “When in good condition and properly aligned, that stack of copper pennies can be conductive. But if one of the pennies is a little bit awry—if its not stacked so well—then you’re not going to be able to get good conductivity. If those bases are mismatched or if there is any other damage to the DNA, as can happen with damage that leads to cancer, the wire is interrupted and electricity will not flow properly.” Essentially, the CIT research indicates, repair mechanisms are triggered in the event that DNA stops conducting electricity property, indicating that it’s been damaged or mutated.

    The investigators hope to develop chip-based biosensors in which an intact stretch of DNA acts as a probe that binds to a complementary sequence contained in a sample. Changes in conductivity that result because the sample DNA is mutated or damaged could be detected as the basis of a disease diagnostic.

    "EDNA is a very fragile and special wire,” Dr. Barton comments. “You’re never going to wire a house with it, and it isn’t sturdy enough to use in popular electronic devices. But that fragile state is exactly what makes DNA so good as an electrical biosensor to identify DNA damage.” 

    Dr. Barton presented her work at the 244th National Meeting & Exposition of the American Chemical Society. 


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