Ultraviolet resonance Raman spectroscopy of bulk and microscopic human colon tissue

A sensitive ultraviolet resonance Raman (UVRR) system, which integrates bulk and microscopic capabilities, is described for use with human tissue. The system incorporates a quasi-continuous tunable laser excitation source in the range 200-300 nm, a liquid nitrogen-cooled charge-coupled device (CCD), a single grating spectrometer, dielectric longpass laser line rejection filters, and cooled specimen holders to minimize bio- and photo-degradation. The system was used on normal human colon tissue, and was compared to our previously used Nd:YAG-based system. Spectra with higher signal-to-noise ratio (S/N) than has previously been achieved, and with less than 5% photobleaching, are presented. The present system outperforms our previous system by improving the S/N in bulk normal colon spectra by a factor of greater than 10. We show for the first time UVRR spectra collected from the various microscopic regions of human colon in a thin section preparation, and the line shapes from the different microscopic morphological components are related to the bulk colon spectra. At 251 nm the epithelial cells and the lamina propria are the major contributors to the UVRR spectrum of bulk colon tissue. Our data suggest that combined bulk and microscopic UVRR spectroscopy of human tissue could provide a valuable tool for bioassay and histochemistry.