| Summary: | For centuries scientists, engineers, and clinicians have been implanting materials into living systems and monitoring material efficacy (e.g., host integration, lifetime, integrity) over time. These studies have inspired a new generation of researchers who have amalgamated biomolecules with synthetic constructs to form bio-hybrid materials to aid in the survivability, stability, and functionality of these constructs. However, the methods used to add biofunctionality to
synthetic materials normally involve costly, time consuming, or energy intensive practices. This thesis describes several strategies that contributed to the synthesis, characterization, and functionalization of new bio-hybrid composites using predominately green chemistries that are not only cost-effect but also adaptable to multiple spatial scales. First, a method to synthesize a bioglass precursor was developed utilizing solvent-accessible primary amines on the extracellular matrix
protein, fibronectin, to catalyze the condensation of silica. Fibronectin, with ~18% primary amine-containing residues and a slightly acidic isoelectric point (~6.0), electrostatically interacted with the silica precursor, tetramethyl orthosilicate, to precipitate nanostructures in aqueous environments (at pH<6). We showed that the magnitude and rate of amorphous silica production could be varied by altering the concentration of fibronectin, illustrating a new pathway for
protein-integrated metal oxides. Next, we adapted a wet-spinning process to fabricate polyethylene terephthalate (PET) microfibers that improves upon the cost and production conditions required of the standard manufacturing methods of melt spinning and electrospinning. Utilizing a modified antisolvent precipitation procedure, a solution of PET solubilized in trifluoroacetic acid was extruded into a water bath to produce polymeric microfibers. We showed that the ultrastructure and
mechanical function of the fibers could be tuned by varying the extrusion orifice diameter, polymer concentration, Reynold's number, temperature, and precipitant concentration. By leveraging the tunability of the wet spinning process, we demonstrated the versatility of our system using two proof-of-concept studies: the first allowed for the incorporation of pH-stable biomolecules during extrusion, and the second enabled the incorporation and activation of a redox-sensitive dye. These
results demonstrate that not only can wet spinning of PET fibers compete with that of melt spinning and electrospinning, but certain application spaces may even be improved by utilizing wet spinning, especially in the design and fabrication of bio-hybrid microfibers. Finally, we discuss the first characterization and utilization of a pristine protein-based hydrogel to actuate a self-folding system. In this study, a gelatin hydrogel was chemically coupled to a polydopamine-coated
metallic scaffold and flexural nylon hinge. Due to the hydrogel's mass comprising >90% water, we could directly control its 3-dimensional structure by regulating water diffusion into and out of the network to elicit controllable shape changes. We took advantage of this change and characterized the actuation behavior using a modified lumped-capacitance model. The rate of folding was modulated by varying the size and cross-linking density of the hydrogel. When taken together, our
findings offer fresh perspectives for designing new bio-hybrid nano, micro, and macro-sized technologies that could conceivably be utilized as implantable and assistive biomaterials.
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