3D nanoelectrodes for bioelectronics : design and characterization of the cell-electrode interface

• 3D-Nanoelektroden für Bioelektronik : Design und Charakterisierung der Zell-Elektroden-Schnittstelle

Santoro, Francesca; Mokwa, Wilfried (Thesis advisor)

Aachen : Publikationsserver der RWTH Aachen University (2014)
Dissertation / PhD Thesis

Aachen, Techn. Hochsch., Diss., 2014

Abstract

During the course of the last decades many endeavors have been made to couple micro electrical engineering devices to biological systems such as the human body. It remains a big challenge to understand how ‘synthetic’ materials can be embedded into living tissues in a way that it is ‘accepted’ by the biological host and maintains its full engineered functionality. In particular, it is of great interest to investigate the long-term response of biological systems which are brought in contact with such biosensors. There is a wide variety of biosensors which can interface cells with electrical activity, such as cells from the heart and the brain. Cardiomyocytes and neuronal cells can elicit such electrical activity in form of action potentials which are fast events in the change of resting membrane potential. Such electrical events can be recorded extracellularly by multi electrodes arrays (MEA) under in vitro conditions. MEAs are chip-based biosensors with metal electrodes in the micrometer range. For decades, the interface between planar electrodes and electrogenic cells has been investigated, and scientists found big limitations in signal-recording/stimulation due to the spatial gap forming between the target cells and the active planar electrodes of a MEA. To overcome these limitations, 3D microelectrodes have been recently proposed considering that a biomimetical shape (mushroom-like shape) can induce a very close and tight contact of the cell on to the electrode. Creating such tight interface massively improves the quality of the recorded signal and the obtained signal is even comparable in shape and amplitude with typical intracellular recording. The presented work investigates the possibility to fabricate 3D metal electrodes with fundamentally two shapes: cylinders and cylinders with caps (mushroom-like). Moreover, the focus of this thesis is to characterize the interface between the fabricated 3D nanostructures and electrogenic cells (HL-1 cells and primary neurons). First, the process of engulfment-like of the 3D nanostructures by the cells has been investigated with particular attention to the cell membrane deformation by scanning electron microscopy and focused ion beam sectioning. An optimal 3D structure has been found in respect of shape and dimensions in the nanometer regime. Moreover, the optimal design has been found in order to reduce as much as possible the gap between the cell and the actual 3D nanoelectrode. In addition these 3D structures have also been fabricated for cell guidance on a grid design to create well-defined networks of cells: this spatial cell arrangement allows studying how cells interact and exchange information via electrical signals within the network. Finally, 3D nanostructures have been fabricated on a MEA together with a guidance grid-pattern to simultaneously guide electrogenic cells and successfully record action potentials. This thesis contributes to predict an optimal 3D nanoelectrode design for improving the cell-biosensor interface. In future works, such 3D nanoelectrodes could be implemented for in vivo biosensors and actuators to record the electrical activity of neuronal or cardiac tissue and moreover, to actively stimulate them.

Institutions

• Chair of Materials in Electrical Engineering I and Institute of Materials in Electrical Engineering [611510]
• Neuroelectronic Interfaces Teaching and Research Area [619420]