Laser Technology Promises Faster Identification Of Bioterror Bugs

Should terrorists strike with biological weapons, how fast scientists could identify the particular “bug” being used might mean the difference between life and death for untold numbers of victims. Physicists at Texas A&M University are conducting experiments to develop a more rapid method to identify airborne bacterial spores.

Initial results of the group’s research, called “FAST CARS,” have been reported in the prestigious Proceedings of the National Academy of Science and offer hope for development of devices to foil the best-laid plans of bioterrorists.

“‘FAST CARS’ stands for femtosecond adaptive spectroscopic techniques for coherent anti-Stokes Raman spectroscopy,” said Marlan O. Scully, physics professor at Texas A&M and member of the National Academy of Sciences. “Airborne contaminants like bacterial spores are usually analyzed by time-consuming microscopic, chemical and biological assays. But the FAST CARS technique would use lasers to detect and identify the unique spectral signatures of such bacteria in real time.”

The FAST CARS team, led by Scully, includes Texas A&M physicists G. W. Kattawar, R. P. Lucht, T. Opatrny, H. Pilloff, A. V. Sokolov, and M.S. Zubairy.

Scully and his colleagues based their idea for FAST CARS on recent experiments in which atoms and molecules were prepared by one or more coherent lasers and then probed by another set of lasers. The ultraviolet radiation given off by particles in the air when excited by lasers can be used to identify which particles are dust and which are bacteria.

“At present, devices are being field engineered that will involve an optical preselection stage based on UV radiation,” Scully observed. “If the fluorescence measurement does not give the proper signature, then that particle is ignored. Most of the time the particle will be an uninteresting dust particle; however, when a signature match is recorded, then the particle is selected for special biological assay.

“The good news about the resonance fluorescence technique is that it is fast and simple. The bad news is that although it can tell the difference between dust and bacterial spores, it cannot differentiate between spores and many other bioaerosols like pollen. That’s why we came up with the idea to use one particular part of the UV spectrum given off by excited particles, called the resonant Raman spectra, to try to more accurately differentiate between different types of biological particles in the air.”

Bacterial spores have been called “amazing life forms,” some of them found to be viable after millions of years. Apparently, the key to spores’ amazing longevity lies in the presence of an acid called DPA in the spores living core where its DNA, RNA and proteins reside.

FAST CARS technology could someday allow scientists to use laser pulses to probe airborne molecules for the presence of DPA, thus speeding identification of particular types of bacteria in the air.

Devices using the FAST CARS model are not yet a reality, but Scully sees them as promising, based on the specific fingerprints of different bacterial spores that could be discovered when they are zapped by laser pulses and yield definitive signatures via analysis with Raman spectroscopy.

“Because each different type of spore would have its own unique mixture of metals and amino acids, it may be the case that the finer details of the Raman spectra would contain spore specific fingerprints,” Scully said. “Clearly, there are many opportunities and open questions implicit in the FAST CARS molecular melody approach to real-time spectroscopy. However it plays out, this combination of quantum coherence and coherent control is a rich field.”

Contact: Judith White, 979-845-4664, jw@univrel.tamu.edu.

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