Clinical Spectroscopic Diagnostics

Applying intravital fluorescence microscopy, we assessed sinusoidal delivery and biliary clearance of two different polymethine dyes. DY635, a benzopyrylium-based hemocyanine dye with shorter excitation wavelength than indocyanine green (ICG), was validated for assessment of hepatic excretory function. Decrease of DY635 and ICG reflecting transcellular transport was 83±4% (DY635) and 14±2% (ICG; p<0.05) over 35 minutes, respectively. In cholestasis, hepatobiliary excretion of DY635 was markedly impaired (control 3176±148 pmol vs. cholestatic 1929±179 pmol; p<0.05). DY635 even enabled an analysis at the single cell level suggesting 1.) hepatocyte uncoupling and 2.) failure of primarily the canalicular pole, allowing real-time insights into molecular mechanisms of this critical facet of hepatobiliary function.