Advancing hepatobiliary diagnosis and treatment using shortwave-infrared fluorescence imaging with ICG-C9.

Indocyanine green (ICG)-C9, a novel cyanine dye developed by the Center for Biosystems Dynamics Research at RIKEN, provides significant advantages over conventional ICG due to its detectability via shortwave-infrared (SWIR) fluorescence imaging. Unlike standard ICG, ICG-C9 facilitates SWIR imaging and displays therapeutic potential when conjugated with antibodies in vivo, suggesting broader applicability across various cancer types. This study evaluated the efficacy of SWIR fluorescence imaging with ICG-C9 in comparison with existing near-infrared (NIR) imaging techniques. We assessed excretion kinetics and the relationship between excitation and fluorescence wavelengths for ICG-C9 and ICG following intravenous administration in BALB/c-nu mice. Tumor uptake was evaluated using a cell-line-derived subcutaneous tumor model from HuH-7 cells, representing hepatocellular carcinoma. Variables including dose, administration route, and exposure time were optimized for comparison. Maximum fluorescence intensity for ICG-C9 was observed with an excitation wavelength of 915 nm and fluorescence emission wavelengths >950 nm within the SWIR spectrum. Both ICG-C9 and ICG followed similar excretion pathways, involving hepatic uptake and biliary excretion. Tumor uptake of ICG-C9 was confirmed under similar conditions to ICG. ICG-C9 demonstrates promising potential as an alternative to NIR fluorescence imaging with ICG, offering unique properties that may enhance imaging capabilities. However, further research is required to establish its clinical applicability and broader therapeutic utility.