Near-infrared-fluorescence imaging of lymph nodes by using liposomally formulated indocyanine green derivatives

Abstract

Liposomally formulated indocyanine green (LP-ICG) has drawn much attention as a highly sensitive near-infrared (NIR)-fluorescence probe for tumors or lymph nodes in vivo. We synthesized ICG derivatives tagged with alkyl chains (ICG-Cn), and we examined NIR-fluorescence imaging for lymph nodes in the lower extremities of mice by using liposomally formulated ICG-Cn (LP-ICG-Cn) as well as conventional liposomally formulated ICG (LP-ICG) and ICG. Analysis with a noninvasive preclinical NIR-fluorescence imaging system revealed that LP-ICG-Cn accumulates in only the popliteal lymph node 1h after injection into the footpad, whereas LP-ICG and ICG accumulate in the popliteal lymph node and other organs like the liver. This result indicates that LP-ICG-Cn is a useful NIR-fluorescence probe for noninvasive in vivo bioimaging, especially for the sentinel lymph node.