Blue crab nanosensor to fight terrorism

Researchers at the University of Maryland have used the chitosan found in the shells of blue crabs from Chesapeake Bay as a component of a nanoscale sensor system. These blue crab nanosensors will be used to improve security in airports, hospitals and other public locations by detecting tiny amounts of explosives or chemicals in air and water.

A substance found in crab shells called chitosan has very useful properties. For example, it has been used in bandages to stop bleeding. But now, researchers at the University of Maryland have used the chitosan from blue crabs living in Chesapeake Bay as a component of a nanoscale sensor system which could save many lives in the future. These blue crab nanosensors will be used to improve security in airports, hospitals and other public locations by detecting tiny amounts of explosives or chemicals in air and water. Read more...

Before going further, below is a close-up view of one of these famous -- and excellent -- blue crabs (Credit and copyright: Science, via EurekAlert!) (Link to a larger version).

Close-up view of a blue crab

These microscopic sensor systems have been developed at the University of Maryland's James Clark School of Engineering.

Clark School engineers are using a substance called chitosan (pronounced "kite-o-san"), found in the shells of the Chesapeake Bay's famous blue crab, to coat components of the microscopic sensor system.

Below you can see how the chitosan was used in the development of the nanosensor. This is an image of the chitosan hydrogel electrodeposited on microfabricated electrode (Credit: University of Maryland) (Link to a larger version).

Chitosan hydrogel

The blue crab nanosensor has been developed by Reza Ghodssi, an associate professor in Clark School, and his team at the MEMS Sensors and Actuators Lab (MSAL).

"Chitosan is interesting because it's a biological compound that can interact with a wide variety of substances, and also work well in a complex, sensitive device," Ghodssi says.

Here are some more details about this nanosensor.

It employs multiple miniature vibrating cantilevers, similar to diving boards, which are coated with chitosan, plus optical sensing technology that can see when the cantilevers' vibrations change.
Different cantilevers can detect different substances and concentrations. When a targeted substance enters the device from the air or water, the chitosan on a specific cantilever interacts with the substance and causes that cantilever's vibration to change its characteristics. The optical sensing system sees the vibration change and indicates that the substance has been detected.

As an example, this is a scanning electron micrograph (SEM) of fabricated microcantilever biosensor used for the detection of DNA molecules (Credit: University of Maryland) (Link to a larger version).

Microcantilever biosensor based on crab shells

This research work has recently been published by the Journal of Micromechanics and Microengineering under the title "End-coupled optical waveguide MEMS devices in the indium phosphide material system" (Volume 16, Number 4, Pages 832-842, April 2006). Here are two links to the abstract and to the full paper (PDF format, 11 pages, 973 KB).

But another article on the same project has also been published by the journal Biomacromolecules under the title "Biofabrication with Chitosan" (Volume 6, Number 6, Pages 2881 -2894, November 2005). And here are the links to the abstract and to the full paper (PDF format, 14 pages, 542 KB).

Sources: The Clark School of Engineering, University of Maryland, via Technology News Daily, July 26, 2006; and various web sites

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