Bacterial Mixture Identification Using Raman and Surface-Enhanced Raman Chemical Imaging

摘要

A number of recent studies by this group and others have demonstrated the ability of normal Raman and surface-enhanced Raman spectroscopy (SERS) to identify bacteria at the species level. Our efforts have focused on the use of colloidal silver as the SERS active substrate. The addition of silver nanoparticles to the bacteria not only produces an enhanced Raman signal, but it also suppresses the native biofluorescence associated with visible laser excitation. Raman chemical imaging uses every pixel or a binned pixel group of the Raman camera as an independent Raman spectrograph. Thus, spatially resolved Raman spectral information is obtained; much like a visual microscope provides spatially resolved visual information. The advantage of this technique in biological detection resides primarily in analysis of biological samples in complex backgrounds without the need for any sample pre- processing. Using a chemical imaging Raman microscope, we compare normal Raman chemical imaging to SERS chemical imaging of a complex mixture of bacteria. In both cases we are able to differentiate single bacteria in the Raman microscope's field of view, but with a substantial reduction in analysis time for SERS chemical imaging.