Distinguishing between apoptosis and necrosis using a capacitance sensor

Apoptosis and necrosis are two different paths for cell death. One of differences between apoptosis and necrosis is the cell morphology. Apoptotic cells shrink without loosing the integrity of their plasma membrane and break into smaller pieces called apoptotic bodies that other body cells recognize and eat. In contrast, necrotic cells swell and their plasma membrane eventually ruptures. Since the cell membrane is closely related to the capacitance (or dielectric constant), we have fabricated a capacitance sensor, which can measure the capacitance of cells, and investigated its time dependence during apoptosis and necrosis for TE2 cells induced by TNF-related apoptosis inducing ligand (TRAIL) and ethanol. The capacitance decreases monotonically during apoptosis. For necrosis, however, step-like behaviors are observed and dips are found in the dC/dt–t curves. The time-lapse images of TE2 cells, which have been taken simultaneously with the capacitance measurements, show that the dips in the dC/dt–t curves are probably due to the rupture of cell membrane. These results suggest that apoptosis and necrosis are differentiated by the capacitance measurements.