Instrumentation for the Control of Biological Function through Electrical Stimulation

Electrical signals play a vital role in the makeup and processing of biological systems. While crucial for desired biological functions, they are also directly involved in degenerative and undesirable activity in these systems. Controlling biological function through targeted electrical stimulation is possible in both non-excitable cells and excitable cells. For each cell type, instrumentation for one specific application is covered in the following. Firstly, this thesis studies electrical stimulation setups and instrumentation for the enhancement of transgene expression in gene therapy. Although the applications of this work are manifold, the focus here is on improving wound healing and tissue regeneration, which is especially important in the treatment of non-closing wounds. Specifically, the ability of iontophoresis to enhance transgene expression in dermal and epidermal cells is assessed. For this, an electrical stimulation circuit with electrodes is developed and employed in in vivo experiments. The genes, in the form of charged DNA plasmids, are injected subcutaneously at the wound border of an adult rat model. An electrical field is applied to the tissue via the electrodes, which forces the plasmids onto a trajectory and forms pores in the cell's membranes to enhance transfection. Various stimulation parameters and setups, as well as different luciferase encoding plasmids, are tested to determine the optimal experimental setup for transgene expression. Secondly, this thesis studies neural implants for the excitation and inhibition of neurons. Neural implants are vital in the treatment of neurological diseases, and allow us to better understand how the brain processes information. The brain is a complex organ which is known to function by its multiple parts working together. Wireless sub-millimeter implants placed individually throughout the brain can imitate natural spatio-temporal stimulation patterns, while causing only minimal tissue destruction. In this thesis, the design of such an implant is elucidated in its entirety, with special focus on the wireless power link. Power from an external primary inductor will inductively be transferred to a secondary inductor that is implanted in the brain. The design trade-offs in selecting the geometry and configuration of the inductors are described and the analysis, simulation, and testing results are presented with the suggestion of an optimal design