Lipase-catalyzed biodegradable polyol polyester synthesis and characterization

Lang, Kening
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Dinolfo, Peter, H.
Corr, David, T.
Gross, Richard, A.
Linhardt, Robert, J.
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The lack of tough biodegradable elastomers underlies one of the most complicated and intriguing challenges in modern bioengineering, the search for affordable and effective mechanical substitutes for tissues. The efforts have included studies of bio-based polyol polyesters owing to their diversity in polymer compositions, structures, and corresponding physicochemical and biological properties. Over the past few decades, multiple polyol polyester architectures have been studied, however, while much progress has been made, relationships between monomer selection, the synthetic method used (including curing), and polyester properties remain unclear. Poly(glycerol sebacate), PGS, a polyol–polyester of glycerol with sebacic acid, has drawn significant attention given its advantageous properties such as ductility, biodegradability, and low biotoxicity. Current chemical synthesis methods rely on polycondensation polymerizations that are not selective, leading to gels unless reactions are quenched at low functional group conversions. The resulting low molecular weight macromers are amorphous and have a melting point below room temperature, which has limited applications. Another limitation of PGS in soft-tissue engineering is its rapid resorption time, which restricts its use to tissues that require relatively long-term mechanical support. In previous studies, lipase catalysis proved effective for the preparation of higher molecular weight glycerol-containing polyesters. In this work, catalysis by immobilized Candida antarctica Lipase B (Novozyme-435) of condensation polymerizations between a set of monomer compositions was studied to prepare PGS and its analogs with better physicochemical properties. It is expected that these developments, coupled with recent major progress in polyol polyester synthesis and ongoing fundamental research on the mechanism of biodegradation, should lead to the development of scalable, high-performance biomaterials that will undoubtedly revolutionize biomedical devices built for in vivo applications. In this thesis, we address the aforementioned challenge by three aspects of effort: 1) lipase-catalyzed synthesis and characterization of poly (glycerol sebacate), 2) enzymatic polymerization of poly(glycerol-1,8-octanediol-sebacate) and its potential on electrospinning, and 3) effects of glycreol/1,8-octanediol molar ratio and curing conditions on the properties of poly(glycerol-1,8-octanediol-sebacate). This work seeks to explore the synthesis of non-crosslinked PGS of higher molecular weight relative to no-catalyst conditions via a regioselective lipase catalyst; the potential that a PGS analogue could be synthesized via N435 catalysis to possess properties that allow its electrospinning into nonwoven fiber scaffolds; and the fine-tuning of the physicochemical properties of poly(glycerol-1,8-octanediol-sebacate) via changing the molar ratio of glycreol/1,8-octanediol and curing conditions. With this effort, it will be possible to design new functional polyol polyesters of importance in biomedical applications where such structural variables are expected to better control mechanical properties, biocompatibility, degradation behavior.
August 2021
School of Science
Dept. of Chemistry and Chemical Biology
Rensselaer Polytechnic Institute, Troy, NY
Rensselaer Theses and Dissertations Online Collection
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