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theses

Current treatments for large volume deficiencies in skeletal muscle tissue have significant drawbacks, and patients suffering from these defects would greatly benefit from a superior solution. Tissue engineers seek to develop a three-dimensional matrix that can serve as a scaffold for muscle cells to regenerate lost tissue. Although substantial progress has been made in growing myoblasts on various scaffolds and promoting fusion into myotubes, plenty of hurdles remain before these scaffolds can be considered the new gold standard treatment. Principally, current scaffolds fail to produce myotubes that are optimally organized and fully differentiated, leading to limited force production. Despite the fusion of myoblasts into myotubes, the tissue lacks some form of stimulation which occurs in the native in vivo environment. This stimulation may be provided by supplementing muscle force with artificial muscles, which are capable of actuation and force production with similar contractile stress to native muscle tissue.
The goal of this project is to utilize a specific type of artificial muscle, called ionic electroactive polymers, to provide electrical and mechanical stimulation to developing myoblasts on a fibrous, conductive scaffold that can provide topographical guidance cues. Thus, this contractile, composite scaffold would seek to closely mimic the in vivo environment of developing skeletal muscle, producing highly organized and differentiated muscle tissue. This project has the following aims: 1) Develop and characterize a biocompatible, ionic electroactive polymer which actuates in an electric field; 2) Develop, characterize, and evaluate the ability of a conductive, fibrous scaffold to promote the organization and differentiation of myoblasts into myotubes; 3) Characterize the in vitro response and evaluate the effect on myoblast differentiation of combined electrical and mechanical stimulation provided by the contractile, composite scaffold resulting from the first two aims.
The movement speed and contractile force of hydrogels made from poly(ethylene glycol) diacrylate and acrylic acid were optimized, but the maximum contractile stress produced fell short of the estimated contractile stress of native muscle fibers. The biocompatibility of the hydrogels was boosted through the addition of a fibrous scaffold synthesized from a copolymer of polycaprolactone (PCL) and polypyrrole (PPy). Cell studies indicated that myoblasts have a clear preference for scaffolds with PPy-PCL compared with scaffolds made from only PCL. Myoblasts exhibited higher attachment, more proliferation, higher numbers of myotubes formed, and a higher fusion index on scaffolds made with PPy-PCL as compared with scaffolds made of PCL. The developed composite scaffold was seeded with myoblasts, and electrical stimulation was applied while the myoblasts were developing. The electrical stimulation patterns seemed to have a net negative effect on the survival of myoblasts, and there was no difference in the progress of differentiation between groups exposed to electrical stimulation and the control groups which received no stimulation. Further experiments are needed to fully control for the complexity of the stimulation patterns use, but this project provides a framework for evaluating the effects of combined stimulation on myoblast development.

ETD_9077

doi:10.7282/T3028W5T

Ph.D.

Includes bibliographical references

by Daniel Patrick Browe

ETD doctoral

The author owns the copyright to this work.