Impedance Spectroscopy as a Label-free Probe of Mitochondrial Membrane Potential

The mitochondrial membrane potential drives the synthesis of adenosine triphosphate (ATP) - the chemical currency of energy for all living organisms. Recent studies suggest that the low-frequency dielectric response, extracted from impedance of a suspension of mitochondria, correlates with their average membrane potential. Energetic electrons donated by molecules extracted from food, build up the proton gradient and membrane potential that drives ATP production. These electrons ultimately recombine with protons and oxygen to form water. Changes in mitochondrial oxygen consumption are therefore expected to correlate with changes in membrane potential and with impedance. We fabricated an impedance probe designed to enable impedance and oxygen consumption rate measurements simultaneously within a respirometer. Further tests include addition of substrates known to affect oxygen consumption, such as ADP, FCCP and succinate. These are used to correlate changes in respiration rate with impedance and, ultimately, mitochondrial membrane potential. Novel substrates, such as excess dopamine, can finally be assessed for possible adverse effects.