Development of novel nanostructured surface enhanced raman scattering substrates for whole microorganism identification

Surfaced- enhanced Raman scattering (SERS) is a powerful technique that provides chemical fingerprints from molecules. This technique is utilizable for fast and accurate identification and characterization of microorganisms. However, obtaining of reproducible SERS spectra from bacteria upon mixing with silver or gold colloidal suspention hinders the use of the technique as a ?Whole Microorganism Identification Technique?. When bacteria sample and silver or gold nanoparticles are mixed, the nanoparticles interact with the bacteria cell wall randomly depending on the surface charge of the nanoparticles and bacteria. Due to the fact that nanoparticles and bacteria cells have to be in close contact for a healty SERS experiment, bringing as many as nanoparticles to contact with bacterial cell wall may improve the quality and reproducibility of the SERS spectra. This study is an effort to utilize the SERS as a fast ?Whole Microorganism Identification Technique?. Therefore, micrometer size wells constructed from silver and gold nanoparticles are prepared with ?Convective Assembly Method? and the bacteri and micro-well size relationship and bacterial concentration and number of micro-wells formed on the surface are investigated. Surfaces, which constructed from silver or gold nanoparticles are prepared with `Convective Assembly Method?, have three dimension. Therefore, bacteria cell walls contact points are increased and provided Raman Scattering enhancement. Escherichia coli and Staphylococcus cohnii was chosen as a model for its bacil shape and gram negative and for its coccus and gram positive features, respectively. The obtained SERS spectra of two model bacteria, Escherichia coli and Staphylococcus cohnii, are compared to the spectra acquired from the same bacterial samples prepared with simple mixing. The results indicate that the SERS spectra obtained from bacteria in the micro-well structure could be used for bacterial identification due to the higher reproducibility and improved quality.