Date of Award
PhD (Doctor of Philosophy)
Professor Andreas Heise
Poly(macrolactone)s, Electrospinning, Electrospraying, Tissue Engineering And Drug-Delivery Systems.
Chapter 1 – Introduction Lactones are a promising class of monomers which enable production of a large number of polymers with different properties. This thesis aims to investigate materials derived from the unsaturated macrolactone globalide and their processing into variable structures by electrospinning and electrospraying. The first chapter provides an overview of the polymerisation techniques, spinning and spraying technology as well as the application of aliphatic polyesters in biomedical applications.
Chapter 2 – Optimization of electrospinning process using poly(globalide). Poly(globalide) (PGl) has not be used in electrospinning to date. In this chapter the spinning conditions were optimised with the goal to obtain homogeneous fibres varying the polymer solution concentration, type of solvent, distance between the collector and the nozzle, voltage and flow rate. The results obtained showed that the process parameters played an important role in the process, which influence the morphology and the diameter of the obtained fibres. Moreover, cell viability tests confirmed that PGl is non-toxic, which qualifies it for the biomedical field.
Chapter 3 – Direct UV-triggered thiol−ene cross-linking of electrospun of poly(globalide) Aiming to improve the mechanical properties of the PGl fibrous scaffolds, the possibilities of obtain a crosslinked fibres was evaluated. For this process, a thiol-ene click reaction during the spinning was applied. The samples obtained using the optimised process, showed that the crosslinking process improved the mechanical properties of the scaffolds. Another characteristic observed with the crosslinked fibres was the capacity of swelling with organic solvent without losing their fibre morphology, which enabled to perform a drugloading by swelling. The cell viability tests confirms that the crosslinking process did not increase the toxicity of the samples and the drug releasing results confirms the possibilities of using this samples in drug delivery system.
Chapter 4 – Biofunctionalization of poly(globalide) fibrous scaffolds. The surface hydrophobicity of the PGl scaffolds could limit cells attachment, promote rejection reactions and consequently interfere with the tissue regeneration efficiency. To overcome this, the surface biofunctionalization of PGl fibres was performed aiming to improve cells attachment and proliferation. For this process, initially amino functional groups were attached to the fibre surface and subsequently using EDC/NHS chemistry a sequence of amino-acid (RGD) was attached to the surface. XPS results confirm the increase of nitrogen concentration on the samples and the cell viability test demonstrated that the cells attachment after day 1 was 9.88 times higher than in the scaffolds without functionalization.
Chapter 5 – Electospraying of poly(globalide) and the production of crosslinked and coreshell microspheres. In this chapter, the possibility of producing PGl microspheres by optimisation of an electrospraying process was investigated. Subsequently, the production of crosslinked particles as well as core-shell structures using poly(ε-trifluoroacetyl-L-lysine) as hydrophilic shell and PGl as hydrophobic core was demonstrated. The results showed that it was possible to obtain particles with good morphology and homogenous diameters. Dye release test confirmed the possibilities of using PGl particles as a drug carrier. The core-shell samples were produced with good morphology; FT-IR and optical microscopy images confirmed the core-shell composition.
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Oliveira F. Electrospinning and electrospraying of unsaturated poly(macrolatone)s: alternative material for biomedical applications. [PhD Thesis]. Dublin: Royal College of Surgeons in Ireland; 2018.