Optimal Excitation Wavelength for Protoporphyrin-ix Fluorescence of Esophageal Adenocarcinoma Cells and Human Barrett Tissue

Fluorescence spectroscopy with six wavelengths (369 nm, 395 nm, 400 nm, 405 nm, 410 nm, 416 nm) was performed to determine the optimal excitation wavelength of exogenously induced Protoporphyrin-IX fluorescence in esophageal adenocarcinoma cells and Barrett’s esophageal tissue, as this might improve (pre)malignant lesion identification in Barrett’s esophagus. Esophageal adenocarcinoma cells OE19 and biopsy specimens from Barrett’s esophageal patients were transplanted onto the chorioallantoic membrane of fertilized hen’s eggs to simulate the in-vivo situation. Administration of 5-aminolevulinic-acid to the cells/biopsy specimens was followed by sequential fluorescence spectroscopy with all light sources and at several time points between 0 hour before and 28 hours after 5-aminolevulinic-acid administration. Afterwards, the biopsy specimens were histological evaluated and classified. From all obtained emission spectra, the Protoporphyrin-IX fluorescence intensity ratio I636/I600 was calculated to determine the highest intensity ratios and highest difference between short and long wavelengths. Fluorescence spectroscopy was performed on 16 OE19 cell samples and 55 biopsy specimens obtained from 17 patients. Our results suggest that the optimal excitation wavelength for Protoporphyrin-IX in OE19 cells and in Barrett’s esophageal tissue lies around 410 nm – 416 nm.