DNA detector: A new ultrafast DNA sensor contains hairpin-shaped DNA strands attached to a gold film. The DNA unfolds when it captures the target gene sequence, and an attached fluorescent molecule glows.
In the other nanosensors being developed for ultrasensitive, rapid DNA detection, researchers are using carbon nanotubes, nanowires, and nanoparticles. All of these approaches promise high accuracy, portability, and low cost. “If you could make a portable device that would sit in your doctor’s office, then, using a small amount of fluid, your doctor could screen you for a genetic abnormality,” says Michael Strano, a chemical engineering professor at MIT who has made nanotube sensors that detect DNA electrically.
Nanosphere in Northbrook, IL, which makes a DNA nanosensor based on research by Northwestern University chemistry professor Chad Mirkin, is far ahead of the game. The Food and Drug Administration has already approved the company’s sensors for certain genetic and infectious diseases, and additional versions are pending FDA approval or in clinical trials.
Nanosphere’s sensor is a microarray coated with DNA strands complementary to the target DNA and incorporated into a test cartridge. Gold nanoparticles, also coated with complementary DNA, are introduced, followed by target DNA, which binds to both the microarray and a nanoparticle. Then the nanoparticle is coated with silver to amplify the light that is scattered from the particle; the light is captured using a digital camera sensor. This method of detection is 100,000 times more sensitive than detecting fluorescence, says William Moffitt, CEO of Nanosphere.
Miller calls Nanosphere’s technology fantastic. However, he adds, Lighthouse Biosciences’s diagnostics test is simpler and requires fewer steps.