Efficiency and Safety of Microstimulation Via Different Electrode Materials

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Summary Our laboratory’s long-term goal is to understand and characterize the effects of microelectrode implantation, recording, and stimulation on brain tissue from a physiological perspective in both neuronal and non-neuronal cells, as well as to improve the biological compatibility, device stability, and performance of neural implants through the use of advanced materials and tissue engineering approaches. The goal of the parent BRAIN initiative R01 project is to understand the charge transfer, electrochemical, and biocompatibility properties of electrodes on the efficacy and safety of microstimulation. Researchers have used Microstimulation to infer functional connections between brain structures or causal links between structure and behavior. Currently, microstimulation therapy is gaining interest for the restoration of visual, auditory, and somatosensory functions in addition to applications in bioelectronic medicine. Current neural stimulation parameters and safety limits were primarily established based on macro electrodes using postmortem histology. They should be revised for microelectrodes using technologies that capture dynamic changes to neural tissue health and function. Another challenge with micro-stimulation is its susceptibility to host tissue responses. Implantation of electrodes causes electrode fouling, progressive neuronal loss, and inflammatory gliosis, leading to decreased stimulation efficacy and increased impedance over long-term implantation. To address these challenges, the specific objectives of this project are to assess the acute efficiency and safety limit of neural stimulation via different electrode materials in vivo (Aim 1), examine the effects of stimulation on electrode materials and cultured cells in vitro (Aim 2), and to characterize the chronic safety and stability of microstimulation in vivo from different electrode materials (Aim 3). Diversity supplement funding is requested to support the research and training of Ms. Anna Kelly, who is a recent graduate of the Bioengineering Department at the University of Pittsburgh. Ms. Kelly will participate in the proposed research as a post-baccalaureate research assistant for at least one year, pending grant approval. Ms. Kelly will conduct research directed toward both acute and chronic mouse studies detailed in the parent award's first and third specific aims. In the acute studies, microelectrodes will be implanted into the cortices of mice expressing genetically encoded calcium indicators and/or genetically labeled microglia expressing a fluorescent protein. Through the use of 2-photon microscopy, the stimulation threshold and efficacy of electrode materials and stimulation parameters will be assessed. After comprehensive training via participating in these experiments, Ms. Kelly will conduct her independent project focusing specifically on the response of the blood-brain barrier and vasculature to microstimulation. In particular, these studies will focus on the potential effect of microstimulation on the leakage of cells and/or plasma and protein from the vasculature and the ensuing response in the brain parenchyma, including potential changes to the morphology and behavior of pericytes and vascular-associated microglia, which have been implicated in BBB leakage in response to inflammation.