The C-2 domain of synaptotagmin I, which binds to anionic phospholipids in
cell membranes, was shown to bind to the plasma membrane of apoptotic cells
by both flow cytometry and confocal microscopy. Conjugation of the protein
to superparamagnetic iron oxide nanoparticles allowed detection of this bi
nding using magnetic resonance imaging. Detection of apoptotic cells, using
this novel contrast agent, was demonstrated both in vitro, with isolated a
poptotic tumor cells, and in vivo, in a tumor treated with chemotherapeutic
drugs.