A pH-Responsive Glycyrrhetinic-Acid-Modified Small-Molecule Conjugate for NIR Imaging of Hepatocellular Carcinoma (HCC)

We report a glycyrrhetinic-acid (GA)-decorated small-molecule conjugate for pH-triggered near-infrared (NIR) fluorescence imaging of hepatocellular carcinoma (HCC). Our in vitro studies demonstrated that the conjugate, referred to as NIR-GA, was efficiently taken up by liver cancer cell lines such as HepG2 and Huh7 through an endocytic pathway mediated by GA receptors. As suggested by co-localization studies, NIR-GA mainly localized in the lysosome, where the acidic pH results in the activation of the fluorescent dye through H+-triggered spirolactam ring opening to give strong fluorescence in the NIR region.