Mitochondria-based biosensors with piezometric and RELS transduction for potassium uptake and release investigations

Dysfunctional mitochondria appear to be involved in many diseases through their role in respiration, reactive oxygen species generation, and energy production. To aid in the design of new biosensors based on mitochondria (MT), we have investigated the feasibility of detecting ion fluxes through the MT-membrane K+-ion channels using piezosensors with MTs immobilized either by hydrogen bonding or thin polypyrrole (PPy) binding film. We have demonstrated for the first time that the mitochondria-based piezosensors are able to detect ion fluxes and thus be utilized for drug development aimed at ion channel opener- or inhibitor-function. The quartz crystal resonator responding only to mass changes in the lower part of the MT film, penetrated by the acoustic wave, is able to detect a pronounced cationic dynamics in PPy-bonded MT piezosensors despite of the undoped-PPy preference for pure anion dynamics. The control experiments performed by resonance elastic light scattering (RELS) confirmed MT swelling/shrinking, ion dynamics, and osmotic water transfer in MTs, as well as the effects of exposure to a drug valinomycin at sub-nanomolar concentrations.