Nano-tetherball biosensor precisely detec...(engineering; Porterfield; and Fisher. ....)

The research was conducted at the Birck Nanotechnology Center and the Bindley Bioscience Center in Purdue's Discovery Park.

The nanotubes have a diameter of about two nanometers, or billionths of a meter, roughly 25,000 times thinner than a human hair.

"The new biosensor is more sensitive than others in two very important respects," Fisher said.

Other sensors require at least five times more glucose to generate a signal, and the new sensor also can operate over a wider range of glucose concentration, which means it could be used for many purposes.

"Depending on where in the body you might want to sense glucose, you would need to detect different concentrations - for example, in the arteries or small intestines or muscles there are significantly different glucose concentrations," Porterfield said.

Being able to sense small quantities while at the same time detecting a wide range of concentrations are two traits that are normally mutually exclusive.

"Other sensors only detect over narrow ranges of specific concentrations," Porterfield said. "Because of the advanced characteristics, this system could be adapted as an all-purpose sensor platform."

The single-wall nanotubes are especially suited for electronic sensors because electricity flows more efficiently through wires only a few nanometers in diameter than it does through ordinary wires.

The engineers have developed a technique to grow individual carbon nanotubes vertically on top of a silicon wafer, a step toward making advanced electronics, wireless devices and sensors using nanotubes. The nanotubes grow out of tiny holes in a "porous anodic alumina template." (This method is described in a previous news release at http://www.purdue.edu/UNS/html4ever/2006/060801.Fisher.vertical.html)

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