Detection of bioagent signatures: A comparison of electrolytic and metal-doped sol-gel surface-enhanced Raman media

Since September 11, 2001, the threat of terrorist attacks and biological warfare within U.S. borders has become a sobering reality. In an effort to aid military personnel and the public at large, we have been investigating the utility of surface-enhanced Raman spectroscopy (SERS) to provide rapid identification of chemical agents directly, and biological agents through their chemical signatures. This approach is based on the ability of Raman spectroscopy to identify molecular structure through the abundant vibration information provided in spectra and the ability of SERS to detect extremely low concentrations (e.g. part-per-billion) through the enhancement of Raman scattering by six orders of magnitude or more. Towards the goal of developing a portable analyzer, we have been studying the ability of two SER media to obtain continuous (i.e., reversible) and quantitative (i.e., reproducible) measurements. Here we compare measurements of nucleic acid-bases, adenosine monophosphate, and ribonucleic acid extracted from Eschcrichia coli, Bacillus subtilis and Staphylococcus aureus obtained by electrolytic SERS and metal-doped sol-gel SERS. The capabilities of these SER media are summarized in terms of rapid detection of B. anthracis and dipicolinic acid.