“Turn-On” NIR-II Fluorescence of a Dually Quenched Probe for Sensitive Imaging of Cathepsin B In Vivo

We designed a NIR-II fluorescence probe, Cys(StBu)-Gly-Phe-Leu-Gly-Lys(AF3)-CBT (AF3-CBT), which forms a dually quenched nanoparticle AF3-NP. Under CTSB cleavage, NIR-II fluorescence turns "On" for sensitive imaging of CTSB. AF3-NP showed 6.1-fold, 3.2-fold, and 2.1-fold higher NIR-II fluorescence intensities compared to those of the control group