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Date of Award

2-2013

Document Type

Campus Access

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Chemical Engineering

First Advisor

Surita R. Bhatia

Second Advisor

Susan C. Roberts

Third Advisor

Gregory N. Tew

Subject Categories

Biomedical Engineering and Bioengineering | Chemical Engineering | Nanoscience and Nanotechnology

Abstract

Polymeric biomaterials represent the leading technologies available today for the repair of tissue damage and for targeted drug delivery. Perhaps the most valuable aspect of polymer-based systems is the extent to which their physical properties (e.g. elasticity, porosity, etc.) can be controlled and tuned by regulating experimental parameters during their synthesis. Biomaterial performance can be improved further still by including supplementary components resulting in a composite material. Synergetic interactions between the constituents of composite materials often results in bulk physical properties that are substantially more than the sum of individual parts. Through understanding and exploiting these sympathetic relationships, novel biocomposites can be developed which exhibit improved efficacy and biocompatibility.

Here we report on the synthesis strategies and characterization of novel biocomposites from our laboratory. We look specifically at hydrogel composites containing a physically-associated network of Pluronic® block copolymer along with a calcium-phosphate mineral component. Rheological results show that composites containing an in situ deposited mineral exhibit a significantly higher elastic modulus than composites of similar composition formed by conventional means. Moreover, analysis of the calcium-phosphate phase of in situcomposites revealed that system parameters such as acidity play an integral role in determining the size and stability of the resultant mineral and subsequently the materials' expected in vivo performance.

Changes to the structure in Pluronic® /calcium-phosphate composite hydrogels during dehydration was investigated to provide a look into the mechanisms involved in composite formation. Small angle X-ray scattering analysis of these systems shows that hydrogen bonding interactions between phosphate ions and the polyethylene oxide (PEO) polymer block significantly impact the nanoscale structure and long-range order contained in these materials. Phosphate groups are preferentially sequestered into the PEO phase in the gel and overall structural changes can be directly related to the average number of hydrogen bonds each phosphate ion experiences. Our results indicate that by understanding how mineralization occurs in simplified systems we may be able to provide insight into the complex mechanisms involved in natural tissue formation. Moreover, we show that by utilizing novel synthesis routes we are able to manufacture new biomaterials with desirable and tunable physical properties.

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