Emission spectra of colonic tissue and endogenous fluorophores.

Autofluorescence emission spectra of normal, adenomatous, and malignant tissues of the colon were compared to that of known fluorophores to indicate the possible causes of tissue fluorescence. Data were collected from normal mucosa (n = 18), adenomatous polyps (n = 32), and adenocarcinoma (n = 18) of the colon. A range of cellular and extracellular fluorophores (elastin, collagen, flavin adenine dinucleotide, nicotinamide adenine dinucleotide, phenylalanine, pyridoxal 5' phosphate, tryptophan, and tyrosine) were similarly examined using a spectrofluorometer with emission and excitation spectrometers. Emission intensities were plotted against wavelength. Wavelengths of peak emission and the width of each peak at half its maximum intensity were measured. Colonic tissue gave four major emission peaks, the wavelengths of which were independent of tissue histology. Tryptophan and collagen type IV appeared to be responsible for two of the peaks. It is possible that NADH may be the cause of a third emission maxima.