Ultraviolet resonance Raman spectroscopy of bulk and microscopic human colon tissue

A sensitive ultraviolet resonance Raman (UVRR) system, which integrates bul k 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 fi lters, and cooled specimen holders to minimize bio- and photo-degradation. The system was used on normal human colon tissue, and was compared to our p reviously used Nd:YAG-based system. Spectra with higher signal-to-noise rat io (S/N) than has previously been achieved, and with less than 5% photoblea ching, 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 mic roscopic 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 p ropria 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.