Surface-enhanced Raman substrate optimization for bacterial identification

The threat of biological agents to soldiers and the civilian community was amply demonstrated in the fall of 2001. We are examining the feasibility of using surface-enhanced Raman spectroscopy (SERS) to detect and identify bacteria. In order to use SERS for bacterial detection and identification, it is necessary to determine the most appropriate type of SERS substrate to use. We are examining gold colloids in suspension, immobilized gold colloids, electrochemically roughened gold, periodic particle arrays (PPA), and film over nanosphere substrates (FONS). Briefly, PPA’s are prepared by depositing gold or silver in the interstitial spaces in a close-packed array of polystyrene nanospheres, while FONS are prepared by depositing approximately half a nanosphere diameter of gold or silver on top of a close-packed array of polymer nanospheres. We are evaluating each of these substrate types to determine which will have a high affinity for bacteria, whether we need to modify the surface of the substrate to attract bacteria, and the degree to which each type of substrate enhances the Raman scattering from the bacterial targets. We will present the results of our initial evaluations of substrates and the spectra obtained for several species of bacteria.