Mutation detection goes wireless
Context: DNA chips for detecting genetic variations abound. Typically, a processed biological sample is placed on a chip, which then must be loaded into a separate, expensive device for reading. Now, Yoshiaki Yazawa and colleagues at Hitachi have designed a tiny chip that not only detects DNA variation but can report it wirelessly from the inside of a sealed sample container. These chips could be dropped directly into a solution containing copies of patient DNA and should be cheap enough to be disposable.
Methods and Results: The chip packs a biosensor, radio transceiver, and antenna coil onto 2.5 by 2.5 millimeters of silicon. An off-the-shelf external unit powers the chip with radio waves and reads its transmissions. To detect a particular DNA sequence, researchers add the complementary sequence to the sample along with the chip. If DNA in the sample binds to the probe sequence, an enzyme emits light. When the sensor on the chip detects the change in light, the radio unit sends a signal to the external unit.
This is a simpler technique than the one used by most other chips, which requires fluorescent dyes, lasers, and microscopes. Additional chips can be added to the sample to boost accuracy or to detect different kinds of variations. Hitachi researchers believe that up to 100 variations could be measured at one time. Also in development are wireless sensors that use the same technology to monitor temperature and pH, which could enable better control of experimental conditions and thus more reliable readings.
Why it Matters: DNA analysis promises to make medicines more effective, if it can be made easy and cheap enough. Hitachi’s chip is the first that can both detect mutations (albeit so far only the simplest and most common kind) and report them wirelessly. Since this kind of chip can transmit data from inside a sealed container, samples tested with it are less likely to be contaminated by researchers or the environment, and samples containing pathogens are less likely to infect workers. Assuming patient samples can be prepared easily for chip analysis, the chip could also make it easier to detect DNA variations in settings less controlled than a research lab. Though the research is still in its initial phases, Hitachi expects that the chips could be used in clinics or small hospitals to help doctors decide which drugs to prescribe for patients.
Source: Yazawa, Y., et al. 2005. A wireless biosensing chip for DNA detection. Paper presented at 2005 IEEE International Solid-State Circuits Conference. Feb. 6–10. San Francisco, CA.