The military recognizes that biological cells are excellent sensors of changes in the environment because they respond to external stimuli with highly reproducible and specific signals. Some toxins cause cells to release oxygen radicals or nitrogen products. Other toxins result in the production of biochemical markers, such as enzymes or growth factors. Toxins may also induce structural or morphologic changes in cells. When cells are embedded in three-dimensional tissue constructs, they not only signal the presence of biological or chemical agents, but can also further indicate physiological consequences of exposure to these analytes.
The Defense Advance Research Projects Agency (DARPA) has initiated the Tissue-Based Biosensors Project, which provides funding to research and private institutions to develop two- and three-dimensional tissue-based biosensors that will accurately and efficiently determine of the presence of biological and chemical weapons. The project specifically seeks to develop cell-based systems that can identify human health risks in the battlefield, improve the performance of cells for detection of chemical and biological weapons, enhance and extend the life of cells used as biosensors and impede the degradation of cellular biosensors when in operational use.
A variety of cell types can be used as biosensors, however, because of their inherent electrochemical nature, a majority of the research in the project focuses on developing neural cells and tissues as biosensors. One group, however, is studying physiological changes in bacteria known as extremophiles, because of their ability to withstand harsh environmental conditions. The systems that result from the research may take the form of three-dimensional scaffolds that harbor and nourish detector cells or flow through systems that identify signal cells. Some of the issues that researchers will address while working on this project include nutrient requirements for cells, transport mechanisms for nutrients and wastes, spatial requirements for cells within a three-dimensional matrix, cell signal detection and stability of tissue-based systems. New materials for culturing and maintaining cells in three-dimensional scaffolds will likely be developed.
█ FURTHER READING:
Defense Advanced Research Projects Agency. "Tissue-Based Biosensors" < http://www.darpa.mil/dso/thrust/biosci/Tbb/index.html > (March 3, 2003).