Surgery (St Vincent's) - Theses
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ItemConstructing a neuromuscular-prosthetic interface and actuator system for limb reconstruction( 2017)A neuromuscular prosthesis provides an ideal solution to functional restoration of the limb after amputation. In such a system, the severed nerves at the stump are implanted into denervated muscles and the innervated muscle is coupled to a human-machine interface which detects the body's signals and transmits it to the actuator. This thesis will present studies that address key components of this bio-prosthetic actuator system, namely the neuromuscular junction, the muscle electrode junction and the actuator system. An in vitro nerve muscle co-culture system was established as a model platform for studying the neuromuscular junction. The effect of agrin and laminin on the innervation of muscle cells was studied with immunocytochemistry, real time PCR and liver cell imaging. Agrin and laminin were found to sensitize muscle cells to innervation by PC12 cells forming more functional neuromuscular junctions and promoting muscle maturation. An in vitro model of the neuromuscular prosthetic interface was created from PC12 neural and primary mice myoblasts grown on multi-electrode arrays. Electrodes of the array were further coated with a conducting polymer polypyrrole to create a low impedance interface between the muscle cells and the electrode. The effect of polypyrrole coating thickness on the quality of the cell recording was assessed. The thickness of polypyrrole coating had no impact on the strength of the cell recording. Finally biocompatibility studies were performed on trilayer polypyrrole based actuators. Trilayer polypyrrole based actuators are known for their superior work density compared to natural muscle and existing actuators. When implanted into rabbit muscle, actuators that had pores engineered into it to encourage tissue integration showed significant polypyrrole delamination from the actuator. The degradation was slowed by sealing the cut edges of the pores on the actuator with polypyrrole. The biocompatibility results provide valuable insight into required design upgrades to existing polypyrrole based trilayered actuators. The work presented in this thesis serve as a basis and platform for further studies in integrating the neuromuscular junction, muscle electrode junction and the actuator into one unit for future translation.