Biosensor Technologies

The detection of biological agents that pose a threat of disease has become an important facet of forensic investigations. A well-known example was the effort of United Nations inspectors to detect microbiological weapons before and following the 2003 Gulf War between Iraq and coalition forces headed by the United States.

Part of these detection efforts involved the use of hand-held devices that could identify the presence of certain bacteria with great precision and sensitivity. These devices represent the cutting-edge application of what are known as biosensors.

Biosensor technology is also used more routinely, for example, in forensic investigations of an illness outbreak or death. The systems currently available for sensing biological analytes rely on two technologies: reporter molecules that attach to anti-bodies and give off fluorescent signals and the polymerase chain reaction (PCR) that amplifies suspect DNA. Because two steps are required to identify biological weapons, the procedure is both labor and time intensive. The Defense Advanced Research Projects Agency (DARPA) initiated the Biosensor Technologies program in 2002 to develop fast, sensitive, automatic technologies for the detection and identification of biological warfare agents. The program focuses on a variety of technologies, including surface receptor properties, nucleic acid sequences, identification of molecules found on the breath, and mass spectrometry.

A major thrust of the surface receptor research is to enhance or replace the chemical signal given off by antibodies to biological analytes. One such project has developed short polypeptides (4–5 amino acids long) that can bind to anthrax spores. A separate group has engineered aptamers, short strands of nucleic acid that specifically bind to the DNA of the bacteria that cause anthrax. Another research area involves using ion channels for amplifying the signal of a reporter molecule. This work includes the engineering of an artificial ion channel that is triggered by the binding of an antibody or other small molecules. Such engineered ion channels are sensitive to a single binding event, require no external energy, and can greatly amplify the chemical signal. Finally, converting phosphors as a replacement for fluorescent reporter molecules is being investigated.

The focus of the nucleic acid sequence technology is the development of a biochip that contains an array of engineered molecules that react with the genome of biological warfare agents or disease causing organisms of public health importance. The biochip is embedded in a platform that is portable, automated, and allows for direct sampling of the environment. A biochip platform to identify the anthrax bacteria is in the testing stages and additional biochips for identifying other harmful bacteria and viruses are in development.