Extracellular stimulation of individual electrogenic cells with micro-scaled electrodes

• Extrazelluläre Stimulation einzelner elektrisch aktiver Zellen mit Mikroelektroden

Eick, Stefan; Offenhäusser, Andreas (Thesis advisor)

Aachen : Publikationsserver der RWTH Aachen University (2010)
Dissertation / PhD Thesis

Aachen, Techn. Hochsch., Diss., 2010

Abstract

The interface between biological and electronic information processing within bioelectronic hybrid systems is an exciting field of research. From an application point of view, it offers the possibility to develop and improve neuroprosthetic devices, e.g. for medical use. In basic neuroscience it enables the investigation of dissociated neuronal cultures or brain slices to elucidate the development, plasticity, and information processing of neuronal networks. To this end, systems and devices for stable long-term investigations with multiple interfaces for extracellular recording and stimulation on a single-cell level are desirable to gain precise access to the network or tissue. The main focus of this work was to study the extracellular stimulation of individual electrogenic cells in vitro with surface-embedded microelectrodes. For this purpose, a new electrophysiological system, including devices and a versatile and customizable amplifier, was developed. The novel amplifier is comprised of a general main amplifier for impedimetric and electrophysiological experiments and multiple headstages specialized for individual chip types including multi-electrode arrays (MEAs) and integrated chips combining stimulation electrodes and recording field-effect transistors. The amplifier was tested and integrated in a patch-clamp setup for intracellular recordings. Microelectrodes with sputtered iridium oxide films (SIROFs) for improved stimulation capabilities were developed in an iterative process. With low impedance and high charge storage capacity, the rough and porous SIROF electrodes showed electrochemical properties superior to conventional gold or platinum electrodes. The biocompatibility and stability of the devices was shown by repeated use for cell growth, electrophysiological experiments, and cleaning of the chips. The new setup and devices were used for experiments with rat cortical neurons and electroactive cell lines. Single Human Embryonic Kidney 293 cells with the NaV1.4 sodium channel could be stimulated to the point of pseudo-action potential (AP) excitation in a controlled manner. The data was analyzed and compared to numerical simulations to investigate stimulation mechanisms and the influence of experimental parameters on stimulation success. For the first time, iridium oxide microelectrodes were successfully employed for extracellular stimulation of individual neurons from a dissociated culture. Two basic stimulation mechanisms were identified, which could both lead to a self-amplifying depolarization of the membrane potential and the excitation of APs. In addition, successful recordings of electrical activity from the HL-1 cardiac myocyte-like cell line were performed. The developed MEAs and SIROF layers showed excellent electrochemical properties, stability, and biocompatibility, and were successfully applied for extracellular stimulation and recording. Hence, they represent an ideal system for the bidirectional communication with electrogenic cells in vitro.

Institutions

• Department of Physics [130000]
• Chair of Experimental Physics 4 B (FZ Jülich) [134210]
• Chair of Materials in Electrical Engineering I and Institute of Materials in Electrical Engineering [611510]