Definition

An imaging agent composed of a pH-low insertion peptide (pHLIP) probe coupled with the near-infrared (NIR) fluorescent dye indocyanine green (ICG), that may be used for cancer imaging using NIR imaging. Upon administration of pHLIP-ICG during surgery, the pHLIP moiety specifically targets and gets inserted into the cellular membrane of tumor cells as the tumor cell environments are more acidic than normal, healthy tissue environments. More specifically, the pHLIP forms an alpha helix and becomes inserted across the cell membrane specifically at the low extracellular pH found within tumors whereas they are unfolded and unbound at higher pHs. Upon NIR imaging, tumor cells and the extent of acidity can be visualized and assessed, marking the tumor cells for surgical removal.