Nanowires track molecular activity

As molecules go, DNA and viruses are relatively large. Many prototype sensors are aimed at detecting large biological molecules, but small organic molecules also play important roles in biological systems, and most pharmaceutical drugs are small molecules.

Researchers from Harvard University have found a way to use transistors made from silicon nanowires to gain information about how small molecules bind to proteins. The nanowires are 20 nanometers in diameter, and the electrical conductance of the devices changes measurably depending on whether target molecules bind to receptor molecules attached to the nanowires. A nanometer is one millionth of a millimeter, or the span of 10 hydrogen atoms.

The nanowire transistors could eventually be used in sensor arrays capable of simultaneously detecting many different molecules, including small organic molecules. The method is potentially capable of rapidly screening drug candidates, according to the researchers.

The researchers' prototype consists of arrays of several dozen sensors that sense when adenosine triphosphate (ATP) molecules bind to the receptor molecules on the nanowires. The researchers showed that the device could measure how effectively the small molecule drug Gleevec blocked the ATP-receptor binding.

The receptor molecule Abl binding with ATP is part of a cell signaling process that, when altered, plays a role in many diseases. Gleevec is used to treat chronic myelogenous leukemia.

The researchers also showed that it is possible to measure the degree to which four other small molecules blocked the ATP binding.

The sensors could be ready for practical use in two to five years, according to the researchers.

The work appeared in the February 14, 2005 issue of the Proceedings of the National Academy Of Sciences.