May 2002

Nanobiotech Makes the Diagnosis

Continued from page 3

By Alexandra Stikeman

DNA Control

In the marriage of nanoelectronics and biology, the most extreme vision involves affixing electronic gadgets directly to molecules. To show how this might work-and why it might be useful-a team at MIT's Media Lab, led by physicist Joseph Jacobson and biomedical engineer Shuguang Zhang, affixed gold particles, each only 1.4 nanometers in diameter, to a piece of DNA. Each gold particle served as a tiny antenna. The researchers then exposed the DNA to radio frequency magnetic fields, causing the particles to heat up, and the double-stranded DNA to break into two strands. When they removed the magnetic field, the strands came back together immediately. "Now we have a very powerful and useful tool that can control things at the molecular level," says Zhang. "So far, there are no tools that can do this. To be able to control one individual molecule in a crowd of molecules is very valuable."

That value, adds postdoc Kimberly Hamad-Schifferli, arises largely from the potential ability to turn genes on and off. To do that, the MIT researchers could attach fragments of DNA to gold particles. When added to a sample of DNA, the fragments would bind to complementary gene sequences, blocking the activity of those genes and effectively turning them off. Applying a magnetic field would then heat the gold particles, causing their attached fragments of DNA to detach, in effect turning the genes back on. Such a tool could give pharmaceutical researchers a way to simulate the effects of potential drugs, which also turn genes on and off. MIT recently licensed the technology to a biotech startup, Waltham, MA-based engeneOS.

Although remote control of DNA may sound more like a parlor trick than something your doctor might use, such experiments are demonstrating that nanoelectronics can interact with biology in powerful ways. Materials like nanowires and nanotubes, extensively researched by physicists and chemists in recent years, are now in the hands of biomedical engineers like MIT's Zhang-with huge implications for everything from drug discovery to diagnosis of diseases like prostate cancer. While it's difficult to predict winners among these many technologies, Berkeley's Alivisatos, for one, says, "I think these things are all going to find competitive niches."

Fast, cheap microelectronics revolutionized the world of computing and information technology. Whether nanoelectronics can revolutionize medicine remains uncertain. But the gap between electronics and biology is fast closing, and biomedical researchers and even physicians will soon have tools to probe life's basic molecules in ways that seemed like fantasy just a few years ago.

Sensing Success
Some companies in nanobiotech