Chloride versus protons : ion currents in the cell transistor junction
Year: 2011
Type: dissertation
Abstract: The cell-transistor junction has been investigated throughout the last two decades. Equivalent electric circuits and various models were devised to reproduce measurements and thus increase an understanding of processes within the junction. In parallel, the minute geometry between an individual electrogenic cell and a field-effect transistor was characterized to fine-tune the models. Surprisingly, all past experiments were entirely based on cations, such as sodium or potassium, disregarding potential applications for anions. In this thesis, the role and influence of anions in the cell-transistor junction was investigated. According to state-of-the-art theory in the field, cations and anions have different effects on measurements, since field-effect transistors show a selective sensitivity for small cations. In order to verify the theoretical expectations, a human embryonic kidney cell line was stably transfected with ligand-gated chloride channels, which provided anion currents upon chemical stimulation. As anticipated, a comparison of recordings with field-effect transistors and inert gold electrodes showed no significant differences. Based on the results obtained from experiments with chloride currents, the recently discovered antiparallel transport of chloride and protons in some voltage-gated chloride channels was investigated. The cell-transistor junction offered the opportunity to reveal the transport of protons in chloride channels since the cation-sensitivity of field-effect transistors induces strong sensor responses upon pH changes. In order to clearly reveal the transport of even smaller amounts of protons, assays were developed to influence pH changes due to buffer concentrations. Signal modeling and simulation was employed to determine the transport stoichiometry of chloride versus protons in voltage-gated chloride channels. Even advanced models of the cell-transistor junction considered only ion currents carried by one single ion species. Therefore, a new comprehensive model of the cell-transistor junction was developed to simulate electric, electrodiffusive and ion-sensitive processes for multiple ion species. In addition, pH and buffer effects were implemented to simulate the influence of transported protons. The shape and attachment of cells was analyzed by means of membrane allocation profiling, a new method developed in the course of this thesis. The results were employed to provide accurate geometrical proportions of the junction for the comprehensive model of the cell-transistor junction. This work unites the fields of cell biology, biophysics and chemistry with microelectronics as well as computational sciences to advance the understanding of cell-transistor junctions. New detail was provided about the junction's geometry. Further, state-of-the-art theories in the field were first confirmed and then improved to develop a comprehensive model of the cell-transistor junction. Finally, the new model was employed to provide insights into the transport stoichiometry of Cl-/H+ antiporters.
Source: JuSER (Forschungszentrum Jülich)
Authors: Frank Sommerhage, Andreas Offenhäusser
Language: English
Subfield: Analytical Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2534457351