The BRP research effort is aimed at the development and testing of micro-electric impedance spectroscopy (mu EIS) and tomography (mu EIT) hardware and reconstruction software to record and image the distribution of electrical properties within the cytoplasm, organelles and membranes of vestibular and auditory sensory hair cells. A combination of flex-circuit technology and standard lithographic microfabrication techniques will be used to construct micro-recording chambers instrumented with arrays of metal electrodes at subcellular dimensions. Cells will be positioned within the recording zone under microscopic observation and interrogated using radio frequency electrical signals. Voltage and current will be measured around the outside surface of the cell and used to reconstruct three-dimensional maps or images of the conductivity and permittivity throughout the cell. Mu EIT systems will be used to interrogate electrical properties of cochlear outer hair cells and type II vestibular hair cells in response to stereocilia displacements, electrical stimuli, and acetylcholine efferent neurotransmitter stimulation. Results will contribute to our fundamental understanding of the spatial distribution and temporal response of electrical properties in these important sensory neurons. Perhaps more importantly, mu EIT devices to be developed as part of the research, will provide an entirely new window through which to view the living machinery of a wide variety of normal and pathological cells. The project integrates bioelectricity, imaging, bioinstrumentation, micro/nano-bioesensors, physiological modeling/computation, biomechanics and microfluidics. Devices involve on-chip transport of solutions/pharmaceutics and living cells. Fabrication and testing of a 10 electrode mu EIS platform, forward modeling, and passive hair cell experiments will be complete by the end of year 1. Multi-electrode mu EIT systems will be fabricated, instrumented, tested and applied to image the spatio-temporal distribution and response dynamics of hair cell plasma and major organelle membranes by the end of year 4.
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