Tiny cell-based chemical detectors have homeland security potential

A highly sensitive, inexpensive "lab-on-a-chip" that provides warning within seconds of even trace amounts of toxic chemicals in water was designed and demonstrated recently by National Institute of Standards and Technology (NIST) scientists and collaborators.

The prototype sensor system monitors the natural response of bacterial cells bound within the microscopic channels of a plastic microfluidics device--a miniaturized chemical and biochemical analysis system. In the presence of certain chemicals, the cells eject large amounts of potassium, which is detected with an optical sensor that changes color. The prototype was demonstrated as part of an early warning system for industrial pollutants that interfere with sewage treatment, but it also has potential homeland security applications.

Cell-based sensors are of great interest today because they can respond to a wide range of chemical toxins rapidly. NIST's primary contributions to this project involve expertise in microfluidics technology, particularly aspects such as plastics processing. The new device has a novel configuration in which, through the use of lasers, tiny posts are constructed within the channels to act as a sieve and promote adhesion of the cells.

Although this type of chemical test could be performed in other formats, a microfluidics device is more sensitive because of the high surface to volume ratio, and also faster because of the close juxtaposition of chemicals and cells. In addition, it consumes less reagent and sample material and could be used in a distributed sensor network for real-time field testing. The device was designed in collaboration with scientists at Virginia Polytechnic Institute and State University (Blacksburg, Va.) and Veridian Pacific-Sierra Research (Charlottesville, Va.).