Polymeric films, emulsions, and nanofibers for medical applications
Yapor, Janet Pamela, author
Reynolds, Melissa M., advisor
Bailey, Travis S., committee member
Li, Yan V., committee member
Van Orden, Alan, committee member
Natural polymers such as cellulose and proteinaceous materials including hair or animal tissue have been used since prehistory. Their use was appropriate until they no longer met the criteria for the intended applications. For example, for implantable materials, the requirements would include materials with higher rigidity or slower degradation than naturally-occurring polymers. For this reason, scientists have invented new materials that are able to emulate or have similar properties as physiological tissue. New materials with a wide range of physical and chemical properties have been tailored to meet the highly diversified demands of modern technologies such as polyurethanes (PU) used for coatings, adhesives, fiber, foams, and thermoplastic elastomers. However, some of these have been derived from petroleum sources, which is a finite resource and its extraction causes environmental contamination. Furthermore, the synthesis of polymeric materials prepared from renewable resources and without the use of external catalysts has been an evolving field in materials science. Polymers such as polyesters have been developed with the goal of decreasing the use of petroleum sources. In addition, synthetic polymers can be tailored to mimic physiological responses. One method for the functionalization of these materials is through the addition of nitric oxide (NO) by the formation of S-nitrosothiol groups. NO is a relevant endogenous free radical that has important physiological roles such as vasodilation, cell proliferation, angiogenesis, and broad-spectrum antibacterial activity. Various NO-releasing platforms have been developed with morphologies that range from viscous liquids and emulsions to films. The synthesis of NO-releasing polyesters with potential applications in wound healing is discussed in this dissertation. Copolymers were prepared via bulk polycondensation with monomeric units including citric acid, maleic acid, and 1,8-octanediol. The first generation of materials required additional conjugation steps in order to add sulfhydryl groups, which were added using carbodiimide chemistry to couple cysteamine or ethyl cysteinate pendant groups. For the second generation of materials, the use of a sulfhydryl-containing monomer, thiomalic acid, eliminated the need for additional conjugation steps. The polyesters were formed using thiomalic acid and 1,8-octanediol alone, and with citric or maleic acid. The increased tensile mechanical properties of the second generation of polyesters yielded materials with Young's moduli similar to that of soft biological tissues such as meniscus, ligament and tendon. The results expanded the potential applications for such polyesters suggesting that the materials could be used as implantable devices or as scaffolds for tissue engineering. An issue with implantable devices arises from the fibrous encapsulation of the device, which is a physiological response referred to as the foreign body response that can be mitigated by NO. Furthermore, an NO-releasing emulsion with additives such as vitamin E and hyaluronic acid was developed, and its NO release profile was studied. In addition to polymer applications, emulation of physiological activities includes materials that can elicit a response when exposed to a variety of chemical or physical environments. Polydiactelyenes (PDAs) are a class of conjugated polymers that have been studied for their potential applications as sensors that detect biological, chemical and thermal changes in the surroundings. These polymers exhibit a chromatic response from blue to red when exposed to various stimuli. PDA nanofibers were prepared via elecrospinning with matrix polymers such as poly(ethylene oxide) and PU.
Includes bibliographical references.
Includes bibliographical references.