Positron Emission Tomography Imaging of Drug‐Induced Tumor Apoptosis with a Caspase‐Triggered Nanoaggregation Probe

Drug Design: An (18)F-labeled caspase-3-sensitive nanoaggregation positron emission tomography tracer was prepared and evaluated for imaging the caspase-3 activity in doxorubicin-treated tumor xenografts. Enhanced retention of the (18)F activity in apoptotic tumors is achieved through intramolecular macrocyclization and in situ aggregation upon caspase-3 activation (see picture).