Polymer composites incorporating engineered electrospun fibres: flexible design and novel properties for biomedical applications

Abstract

Due to their unique structure and flexible choice of materials, electrospun degradable and biocompatible polymer fibres are considered to be extremely suitable for biomedical applications such as tissue engineering and drug delivery, either on their own or integrated within composites. Conventional electrospun fibre composites are typically based on non-woven mats and therefore limited to simple-curved geometries (films, membranes, etc.). For aqueous composites such as hydrogels, the hydrophobicity of the materials sometimes prohibits fibres to be easily integrated or distributed in these composites. In this thesis, a review on the topic is firstly presented in Chapter 2, introducing and discussing engineering of electrospun fibre as well as their biomedical applications. In Chapter 3, electrospun polylactide (PLA) fibres reinforced poly(trimethylene carbonate) (PTMC) composites are prepared. The composites are loaded with both continuous and short PLA fibres, achieving significant mechanical enhancement and offering opportunities to produce composites conveniently using liquid formulations. Chapter 4 presents the development of shape memory polymer composites based on a combination of PLA fibres and a PTMC matrix. By loading different amounts of short fibres with different aspect ratios or by using plasticisers, the shape memory behaviour is modulated; and composites of more complex geometries are produced. In Chapter 5, PTMC-PLA fibre composites are made into drug release system. Dexamethasone-loaded PLA fibres are integrated into a PTMC matrix, showing sustained drug release and stimulating stem cell osteogenic differentiation. This concept gives promise to loading various drugs into photo-crosslinked structures without denaturation. In Chapter 6, electrospun PLA fibres are functionalized by amphiphilic block copolymer polylactide-block-poly[2-(dimethylamino)ethyl methacrylate] (PLA-b-PDMAEMA) for the development of carboxymethylcellulose composites hydrogels. Functionalization of PLA fibres not only allows for easy integration and dispersion into the hydrogel, but also enhances the interfacial bonding between fibre and hydrogel. In the last chapter (Chapter 7), some conclusions are drawn and future works are discussed.