Abstract
Micro-fabricated neural electrode arrays, placed in the nervous system to directly interface with neurons, have tremendous research and clinical significance. Current arrays experience chronic failure including signal drift and degradation due to biochemical, mechanical and electrical mismatch between the artificial device and brain tissue. Several bioengineering strategies are being investigated towards a seamless and stable neural electrode-tissue interface. The first strategy is to camouflage the abiotic implant with biomolecules. A neural adhesion molecule L1 has been coated onto the implant surface showed to improve neuronal growth on and around the implant and reduce microglia activation. Excitingly, preliminary experiments showed that L1 drastically improved the recording yield and longevity of neural electrode arrays. The mechanism and longevity of the coating as well as alternative biomolecules for immobilization are currently being investigated. Secondly, therapeutics to modulate the host tissue responses such as inflammation, degeneration, BBB breach and oxidative stress may be applied. Thirdly, it has been hypothesized that the mechanical mismatch between the stiff device and soft brain tissue acerbates the chronic tissue responses. Current arrays are mostly made of materials that are 3-6 orders of magnitude stiffer than the brain tissue. To overcome this issue, new materials and designs are being developed that matches the mechanical properties of the brain. An elastomeric electrically conductive polymer blend is synthesized that has the mechanical modules similar to that of brain tissue (modulus of 130 kPa). In vitro culture assays showed that soft wires made of the new materials recruited and activated less microglia in culture than the stiff microwires, typically used to assemble chronic neural arrays. In vivo histology of the soft wire implant showed much better integration with the host tissue compared to the stiff wires. Lastly, to better characterize the cellular and vascular response at the interface and better understand the relationship between tissue reactions and recording performance, new methods of chronic neural recording evaluation as well as live-animal multi-photon imaging have been developed. The ultimate solution to a reliable and seamlessly integrated neural interface may be a combinatorial approach that takes advantage of multiple strategies discussed above and beyond.
Biography
Dr. Tracy Cui is an Associate Professor of Bioengineering at the University of Pittsburgh and the Director of the Neural Tissue/Electrode Interface and Neural Tissue Engineering Lab. In Dr. Cui’s lab, the primary research focus is on the interactions between neural tissue and smart biomaterials. Research areas include the neural electrode-tissue interface, neural tissue engineering, drug delivery, and biosensors.
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