Monitoring of Traumatically Injured Organotypic Hippocampal Cultures with Stretchable Microelectrode Arrays

Abstract

ABSTRACTTraumatic brain injury (TBI) can be caused by motor vehicle accidents, falls and firearms. Approximately 2% of the US population lives with disabilities cause by TBI. To discover mechanisms of functional deficits underlying TBI, as well as to develop strategies to restore lost function with neural interfaces, we developed a stretchable microelectrode array (SMEA), which can be used for continuous recording of neuronal function, pre-, during, and post-stretch injury. The SMEAs were fabricated on elastomeric substrates, consisting of stretchable 100μm wide, 25nm thick gold electrodes patterned on a polydimethylsiloxane (PDMS) substrate, and encapsulated with a 10-20μm thick, photo-patternable silicone (WL-5150, Dow Corning) insulation layer. Finally, the SMEA was packaged between two printed circuit boards and mounted in a commercial Multi Channel Systems amplifier. Combining with our TBI model, which can generate precise and reproducible injury of hippocampal cultures, SMEAs were able to monitor the extracellular field potentials of neuronal populations within the cultures grown on SMEAs and injured by bi-axialy stretching the stretchable membranes. Previous biocompatibility tests showed no overt necrosis or cell death caused by the SMEAs after 2 weeks in culture [2]. The electrical performance of the SMEAs was tested in electrophysiological saline solution before, during and after biaxial stretching. The initial electrode impedance at 1kHz was ∼2kΩ. The SMEA was stretched to 8.5% biaxial strain. The microelectrode impedance increased with the strain to reach 800kΩ at 8.5% strain. Upon relaxation, the impedance recovered to 10kΩ. The working noise level of the sMEA remained below 20 ΩVpp during the whole process. New methodologies for improving the design of microelectrode arrays structure, the choice of materials and the new technology of fabrication were tested on gold microelectrode arrays supported on glass. By using the prototype arrays, population spikes were able to be recorded from organotypic hippocampal slice cultures of brain tissue. Our results demonstrate that the prototype arrays have good electrical performance compatible with existing multielectrode array systems. Moreover, the results indicate the ability of the prototype arrays to record neuronal activity from hippocampal slices. This novel technology of SMEAs will enable new studies to understand injury mechanisms leading to post-traumatic neuronal dysfunction.