Bacterial Detection via Surface‐Enhanced Raman Spectroscopy (SERS)

Abstract

Surface‐Enhanced Raman Scattering (SERS) is a sensitive and label‐free detection technique that takes advantage of the large enhancements in Raman scattering of molecules adsorbed onto roughened or nanofabricated metallic surfaces. Since its discovery in the 1970s, SERS has been harnessed for sensing a wide variety of molecules, including drugs and biological molecules, and more recent work suggests that it can be a powerful method for bacterial identification. Here we provide a comprehensive review of bacterial detection via SERS, highlighting a key observation in the literature that bacteria, when deprived of nutrients, undergo a stress response that correlates with the release of biomolecules that can be detected by SERS. Such SERS spectra are consistent with sensing of purine‐based metabolites that presumably arise from rapid RNA degradation in bacteria in the absence of nutrients. Intriguingly, the SERS spectra from different bacteria appear to be unique, suggesting that this method can be used for “fingerprinting” bacteria. We subsequently describe new results to better understand bacteria SERS by employing unique SERS substrates designed at HP Inc as well as HP’s state‐of‐the‐art inkjet dispensing technologies for sample exposure. Our results provide evidence for time‐dependent release of purine metabolites by nutrient‐deprived bacteria which we suggest may be used as an additional parameter to further classify different types of bacteria. The ability to merge inkjet dispense with SERS (ID‐SERS) creates the possibility of using SERS for bacterial detection, quantification, and antibiotic susceptibility testing which, in turn, may have significant implications in healthcare and the life sciences.