Molecular Recognition Mechanisms for Detecting Cell Death In Vivo

The noninvasive detection of cell death has significant diagnostic values. Molecular events in apoptosis and necrosis are a source of valuable surrogate markers for the detection of cell death. Two classes of imaging agents are being developed for imaging caspase activities and redistribution of membrane phospholipids, respectively. The current review looks at the molecular recognition mechanisms of existing and emerging agents in the physiological context of the surrogate markers. The imaging of caspase activities using substrate-derived agents has the advantage of high selectivity and can potentially allow the dissection of individual apoptotic pathways in vivo. The detection of membrane phospholipid redistribution using extracellular agents has the advantage of high target density and accessibility. The strength and limitations of each approach are discussed. Overall, in order to develop appropriate imaging techniques, it is important to understand the interactions between the agent and surogate markers on a molecular as well as physiological level. Such information is vital for fully appreciating the potential utilities of an imaging strategy.