Developing poly(polyol sebacate)-based elastomeric biomaterials for soft tissue engineering
thesisposted on 22.02.2017 by Li, Yuan
In order to distinguish essays and pre-prints from academic theses, we have a separate category. These are often much longer text based documents than a paper.
Biodegradable soft elastomeric biomaterials are desired in the application of soft tissue engineering and a new family of crosslinked elastomers, poly (polyol sebacate) (PPS), have shown promises in applications of nerve, vascular and myocardial tissue engineering. However, a number of problems remain with these novel polymers, including the poor reproducibility in the synthesis and properties of PPS, the toxicity of very soft versions of the PPS family, and too rapid degradation rates. Therefore, this PhD thesis project aims to address these issues and develop soft, degradable elastomers with improved reliability, biocompatibility and satisfactory degradation rates. The major results include: (1) The poor reproducibility of poly(glycerol sebacate) (PGS) was caused by the evaporation of small molecule, glycerol; and the satisfactory biocompatibility and reasonable slow degradation rate of PGS could only be achieved by a long curing time with a compromise of mechanical elasticity. (2) In order to achieve a satisfactory combination of mechanical flexibility and degradation rate, a larger monomer, xylitol, was used to replace glycerol to synthesize poly(xylitol sebacate) (PXS). A comparative study on PXS and PGS demonstrated that PXS polymers had better mechanical elasticity (twice elongation) than PGS of the same crosslink density, whilst their degradation rate and biocompatibility were similar to those of PGS counterparts. (3) The degradation mechanisms of PGS and PXS was further investigated in vitro and it demonstrated that all the materials underwent esterase enzymatic and free radical synergistically degradation. (4) In order to achieve nonlinear elasticity of soft tissue, an elastomeric PXS scaffold was fabricated by core/shell electrospinning technique using PXS as the core material and polyvinyl alcohol (PVA) as the shell polymer, with PVA shell being washed off after PXS curing. The newly fabricated PXS scaffold exhibited softer and remarkably higher rupture elongation than PXS sheet in aqueous conditions. In conclusion, soft, degradable elastomeric biomaterial with improved reliability, biocompatibility and satisfactory degradation rates could be achieved from the elastomer PXS using the core/shell electrospinning technique. The produced PXS fibrous scaffold demonstrated a high potential in soft tissue engineering in terms of biocompatibility, mechanical properties and degradation kinetics. Further work shall focus on in vivo evaluation of the PXS fibrous scaffold.