Optical and Electrochemical Probes for Monitoring Cytochrome c in Subcellular Compartments During Apoptosis

Cytochrome c (Cyt. c) is a key initiator of the caspases that activate cell apoptosis. The spatiotemporal evaluation of the contents of Cyt. c in cellular compartments and the detection of Cyt. c delivery between cellular compartments upon apoptosis is important for probing cell viabilities. We introduce an optical probe and an electrochemical probe for the quantitative assessment of Cyt. c in cellular compartments at the single cell level. The optical or electrochemical probes are functionalized with photoresponsive o-nitrobenzylphosphate ester-caged Cyt. c aptamer constituents. These are uncaged by light stimuli at single cell compartments, allowing the spatiotemporal detection of Cyt. c through the formation of Cyt. c/aptamer complexes at non-apoptotic or apoptotic conditions. The probes are applied to distinguish the contents of Cyt. c in cellular compartments of epithelial MCF-10A breast cells and malignant MCF-7 and MDA-MB-231 breast cells under apoptotic/non-apoptotic conditions.