Date of Award:

5-2016

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Biological and Irrigation Engineering

Advisor/Chair:

Randolph V. Lewis

Abstract

Orb-weaving spiders produce six different types of silks, each with unique mechanical properties. The mechanical properties of many of these silks, in particular the dragline silk, are of interest for various biomedical applications. Spider silk does not elicit an immune response, making it an ideal material for several applications in the medical field. However, spiders cannot be farmed for their silk as they are cannibalistic and territorial. The most reasonable alternative for producing spider silk fibers is to utilize genetic engineering to produce the proteins in a foreign host and then spin fibers from the synthetic protein. Spider silk-like proteins have been expressed in transgenic goats on a scale sufficient to spin synthetic fibers. To spin it, the protein is dissolved in a solvent to create a viscous spin dope. This spin dope is extruded into a coagulation bath where it forms a fiber. Fibers spun in this manner have poor mechanical properties and are water soluble, unlike natural spider silk. By applying a post-spin draw, the mechanical properties of the fibers improve and they are no longer water soluble. This increase occurs because β-sheets, important secondary structures, form and begin to align parallel to the fiber axis. In previous work, post-spin draw has been applied by hand to the fibers after initial spinning. This is not a viable method for the commercial production of synthetic spider silk. The first aim of this research was to design, test, and optimize a mechanical system that can create consistent, synthetic spider silk fibers. The second aim of this research was to discover how parameters such as solvents, temperature, spinning speed, additives, and post-spin draw, among other variables, affect the properties of synthetic spider-silk proteins purified from goat milk. As part of this research, a mechanical system that can perform these treatments while the fiber is being made was designed, built and tested. This system was built with the intent to inform the creation of a process for the creation of a synthetic on an industrial level.

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