Date of Award

5-2017

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Bioengineering

Committee Member

Dr. Delphine Dean, Committee Chair

Committee Member

Dr. Marian Kennedy, Co-Committee Chair

Committee Member

Dr. Melinda Harman

Abstract

Micropatterning on a surface using fibers, channels, and troughs, can act as an effective means of inducing cell attachment and alignment. These morphological and pattern changes as a response to physical cues can impact the potential that a cell has to differentiate into a different cell line. This thesis evaluated the response of human dental pulp stem cells (DPSCs), and other cell types, to spider dragline silk fibers, a potential scaffold material for tissue regeneration, and further observed the effects of morphology, orientation, and composition of silk on the adherence of cells. Several cell lines were studied in this thesis, including adipose derived stem cells (ADSCs), osteoblasts (7F2s), and fibroblasts (3T3s), but DPSCs were the main cell type of interest. This is due to the fact that DPSCs are a proposed source of stem cells for nerve regeneration based on their close embryonic origin to neurons and the ease with which DPSCs can be obtained from a donor. The cells' morphologies and spread patterns were characterized after they were plated onto Nephila clavipes dragline fibers in media. The inclusion of 3T3s and 7F2s in this study allowed for both direct comparisons to prior published work and a qualitative comparison to the morphology of the DPSCs. After twelve days, the DPSCs exhibited greater relative alignment and adherence to the spider dragline fibers than the 3T3s and 7F2s when silk was wrapped in an aligned orientation rather than a random orientation. The impact of a common sterilization method (ultraviolet light) on the spider dragline fiber surface and subsequent cell response to this modified surface was also characterized. Exposure of the silk to ultraviolet light did not have a measureable effect on cell alignment, but it did eliminate bacterial growth and changed fiber surface roughness. Spiders' exposure to stressful environments did not have an effect on silk to impair cell alignment or adhesion, and synthetic recombinant protein silk fibers did not act as a scaffold for cell adhesion or alignment. However, cells remained viable and proliferative in recombinant silk hydrogels, suggesting that surface characteristics and large diameter had a negative impact on cell interaction on "˜synthetic' silk fibers. In all cases, natural drawn spider silk acted as an effective scaffold for cellular adhesion and alignment of DPSCs and could be used in neural differentiation applications. Collectively, this thesis indicates that spider silk from spiders under any extent of stress can be rendered sterile by UV radiation and act as an effective means of cellular adhesion and alignment when silk is organized in an aligned orientation.

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