Mitochondrial Membrane Studies Using Impedance Spectroscopy with Parallel pH Monitoring

Abstract

A biological microelectromechanical system (BioMEMS) device was designed to study complementary mitochondrial parameters important in mitochondrial dysfunction studies. Mitochondrial dysfunction has been linked to many diseases, including diabetes, obesity, heart failure and aging, as these organelles play a critical role in energy generation, cell signaling and apoptosis. The synthesis of ATP is driven by the electrical potential across the inner mitochondrial membrane and by the pH difference due to proton flux across it. We have developed a tool to study the ionic activity of the mitochondria in parallel with dielectric measurements (impedance spectroscopy) to gain a better understanding of the properties of the mitochondrial membrane. This BioMEMS chip includes: 1) electrodes for impedance studies of mitochondria designed as two- and four-probe structures for optimized operation over a wide frequency range and 2) ion-sensitive field effect transistors for proton studies of the electron transport chain and for possible monitoring other ions such as sodium, potassium and calcium. We have used uncouplers to depolarize the mitochondrial membrane and disrupt the ionic balance. Dielectric spectroscopy responded with a corresponding increase in impedance values pointing at changes in mitochondrial membrane potential. An electrical model was used to describe mitochondrial sample’s complex impedance frequency dependencies and the contribution of the membrane to overall impedance changes. The results prove that dielectric spectroscopy can be used as a tool for membrane potential studies. It can be concluded that studies of the electrochemical parameters associated with mitochondrial bioenergetics may render significant information on various abnormalities attributable to these organelles.

Towards non-invasive characterisation of coronary stent re-endothelialisation – An in-vitro, electrical impedance study

“…The reactance of a cell is determined by the capacitive effect of the cell membrane and various organelles within [ 57 , 58 ]. The shape and arrangements of these organelles and membranes are matched to each cell’s specific functionality and it is therefore reasonable to assume that capacitive reactance measurements of these elements of the cell will reveal differences between cell types [ 26 , 59 ], as presented here. It is acknowledged that impedance measured across a frequency range will report results from different regions of a cell monolayer, with the current path at low frequencies bypassing the cell membrane and measuring the paracellular space whilst higher frequencies are transcellular, through the cells interior [ 43 , 58 , 60 , 61 ].…”

“…In-vitro use of impedance spectroscopy has been extensively used to non-invasively gain insights into a wide range of cellular behaviours such as micromotion [ 25 ], mitochondrial dysfunction [ 26 ], stem cell differentiation [ 27 – 29 ] and EC barrier function [ 30 , 31 ]. This research has been greatly facilitated by the availability of commercial impedance systems such as Applied Biophysics, ECIS system and ACEA Biosciences xCELLigence range.…”

Measurement of Technetium-99m Sestamibi Signals in Rats Administered a Mitochondrial Uncoupler and in a Rat Model of Heart Failure

“…In isolated mitochondria, membrane potential is calculated by monitoring the distribution of the cations between the incubation medium and mitochondrial matrix, and these are generally reported to be high, i.e ., 172 mV [ 10 ], 196 mV [ 11 ], and 210–220 mV in isolated liver mitochondria [ 12 ] and around 190 mV in isolated brain mitochondria [ 13 ]). Impedance spectroscopy with parallel pH monitoring showed a potential of 144 mV in isolated heart mitochondria [ 14 ]. For intact cells, the fluorescent membrane-permeant cationic probe tetramethylrhodamine ethyl ester (TMRE) is a probe that is frequently used probes for analyzing mitochondrial membrane potential [ 8 ].…”

Cell secretion from the adult lamprey supraneural body tissues possesses cytocidal activity against tumor cells

“…Moreover, mitochondria adapt to varying energy requirements, which change in response to energy consumption and control the production of reactive oxygen species (ROS). Mitochondria function relies on complex ion transfer processes that occur within various protein complexes present at the inner membrane (Padmaraj et al 2014 ).…”