Graduation Semester and Year

2012

Language

English

Document Type

Thesis

Degree Name

Master of Science in Biomedical Engineering

Department

Bioengineering

First Advisor

Liping Tang

Abstract

Interfacing high degree-of-freedom robotic prosthetics directly to the peripheral nervous system aims at improving the quotidian life of amputees. Despite advancements in robotics that have lead to human-like upper limb prosthetics, long-term interfacing has not been accomplished, thus voiding them from clinical use. Interfacing electrodes in the central nervous system fail due to the foreign body reaction and glial scar formation at the site of implantation. Concrete mechanisms for the failure of long-term Interfacing at the peripheral nervous level remain unclear. A regenerative multi-electrode interface (REMI) which allows for action potential recording as early as 7 days and provides support to bridge transected nerve gaps has been recently tested. However, the REMI, similarly to other electrode arrays, suffers from decay in action potential signal acquisition after an extended period of time. Today, amputees would not be interfaced immediately after amputation; therefore, the effects of a subchronic amputation must be studied to evaluate the peripheral nerve reaction to interfacing, in this case, implantation of a REMI. A 30-day subchronic amputation condition was simulated by transecting the sciatic nerve, ligating the distal stump, and suturing the proximal stump to the biceps femoris muscle of twelve female adult Lewis rats. Floating multi-electrode arrays comprising 18 Pt/Ir electrodes, placed in collagen-filled Polyurethane tubes, were implanted after subchronic amputation in the animals by suturing the stumps of transected sciatic nerve to the tube. The REMI , along with the nerve regenerate, was explanted after 15, 30, and 60 days. Reactive macrophages, visualized by immunofluorescence of ED1 labeling, showed a significant reduction in size between 15 and 60 days post REMI implantation for acute and subchronic amputation conditions. The progressive decreasing pattern indicates that scar formation around the electrodes does not directly affect the action potential signal acquisition; regardless, it may still play a minor role in interfacing failure. Axonal regeneration and remyelination were examined by immunolabeling with NF200 and P0, respectively. Axonal regeneration and remyelination between subchronic and acute amputation conditions revealed comparable results 15 post-injury. The complete remyelination of the axons correlates with the maximum percentage of active channels; however, it does not account for the eventual signal decay. Blood nerve barrier integrity was evaluated to determine whether tight junction formation and/or distribution has an effect on ion diffusion in the extracellular matrix. Through the use of anti-Claudin-1 antibodies, a progressive distribution and organization of tight junctions around and through the axons was observed for acute and subchronic amputation conditions. Foreign body response, axonal regeneration, remyelination, and BNB formation results indicate that a subchronic amputation does not significantly affect the peripheral nerve regenerating properties when compared to the acute amputation conditions. Further, it is hypothesized that tight junction concentration and distribution throughout the peripheral nerve plays an important role in the eventual failure of peripheral nervous interfacing

Disciplines

Biomedical Engineering and Bioengineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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