Characterizing the origin of autofluorescence in human esophageal epithelium under ultraviolet excitation.

The autofluorescence under ultraviolet excitation arising from normal squamous and columnar esophageal mucosa is investigated using multispectral microscopy. The results suggest that the autofluorescence signal arises from the superficial tissue layer due to the short penetration depth of the ultraviolet excitation. As a result, visualization of esophageal epithelial cells and their organization can be attained using wide-field autofluorescence microscopy. Our results show tryptophan to be the dominant source of emission under 266 nm excitation, while emission from NADH and collagen are dominant under 355 nm excitation. The analysis of multispectral microscopy images reveals that tryptophan offers the highest image contrast due to its non-uniform distribution in the sub-cellular matrix. This technique can simultaneously provide functional and structural imaging of the microstructure using only the intrinsic tissue fluorophores.