In Vivo Time-Resolved Fluorescence Imaging of a NIR FRET Probe in Live Mice

One of the key challenges in anti-cancer drug validation is to quantitatively discriminate in vivo non-specific receptor-independent tumor accumulation from receptor-mediated uptake into the tumor cells. To overcome this challenge, we develop a new near-infrared Förster resonance energy transfer fluorescence lifetime imaging (NIR FRET FLIM) technique. We apply herein this novel approach to monitor and characterize cellular uptake in both cancer cells and normal cells in vitro and in vivo. Our results demonstrate that NIR FRET FLIM can quantitatively distinguish receptor-bound from unbound donor in live animals with high sensitivity and high accuracy. Thus, it has a great potential for the quantitative detection of targeted delivery systems for diagnostic and therapeutic use.