Electrospun Polymeric Scaffolds with Enhanced Biomimetic Properties for Tissue Engineering Applications

This PhD Thesis is focused on the development of fibrous polymeric scaffolds for tissue engineering applications and on the improvement of scaffold biomimetic properties. Scaffolds were fabricated by electrospinning, which allows to obtain scaffolds made of polymeric micro or nanofibers. Biomimetism was enhanced by following two approaches: (1) the use of natural biopolymers, and (2) the modification of the fibers surface chemistry. Gelatin was chosen for its bioactive properties and cellular affinity, however it lacks in mechanical properties. This problem was overcome by adding poly(lactic acid) to the scaffold through co-electrospinning and mechanical properties of the composite constructs were assessed. Gelatin effectively improves cell growth and viability and worth noting, composite scaffolds of gelatin and poly(lactic acid) were more effective than a plain gelatin scaffold. Scaffolds made of pure collagen fibers were fabricated. Modification of collagen triple helix structure in electrospun collagen fibers was studied. Mechanical properties were evaluated before and after crosslinking. The crosslinking procedure was developed and optimized by using - for the first time on electrospun collagen fibers - the crosslinking reactant 1,4-butanediol diglycidyl ether, with good results in terms of fibers stabilization. Cell culture experiments showed good results in term of cell adhesion and morphology. The fiber surface chemistry of electrospun poly(lactic acid) scaffold was modified by plasma treatment. Plasma did not affect thermal and mechanical properties of the scaffold, while it greatly increased its hydrophilicity by the introduction of carboxyl groups at the fiber surface. This fiber functionalization enhanced the fibroblast cell viability and spreading. Surface modifications by chemical reactions were conducted on electrospun scaffolds made of a polysophorolipid. The aim was to introduce a biomolecule at the fiber surface. By developing a series of chemical reactions, one oligopeptide every three repeating units of polysophorolipid was grafted at the surface of electrospun fibers

Glosarium Kimia

386 p.; 24 cm

Synthesis, Applications and Biological Impact of Nanocellulose

This book aims to highlight recent advances in the synthesis of nanocellulose and surface modifications for the design of functional nanocellulose, as well as its applications and potential biological impact. It features two review articles and four original research articles which targets a broad readership of chemists, materials scientists, biochemists, nanotechnologists and others with an interest in nanocellulose research

Exploring the Sonication Behaviours of Liquid Metals

Liquid metals are a class of materials that melt below or at near room temperature. Among the family of liquid metals, gallium and gallium-based alloys exhibit extraordinary functional features including metallic electrical and thermal characteristics, reactive surfaces rich in free ions and electrons, fluidity, and a tuneable oxide layer. Besides the exploration of the bulk of liquid metals, the mechanical synthesis of micron and nano-sized droplets is increasingly reported. Droplets of liquid metals, with increased surface-to-volume ratio, are increasingly shaped and dispersed utilising the sonication technique as a simple and straightforward method. The sonication process also briefly exposes the liquid metal surfaces to potential chemical and physical alterations. However, the sonication behaviours of gallium and gallium-based alloys are yet to be fully explored and the possibility for functionalisation is left uncovered. In this thesis, the author presents three different sonication combination setups with multiple controlling factors and finely tuned sonication conditions for synthesising functional materials from liquid gallium and gallium-based alloys. In the first stage of this Ph.D. thesis, the author establishes a pathway for room temperature nitridation of a gallium alloy utilising the sonication technique for the formation of gallium nitride, an important functional gallium compound. The room temperature sonication process utilised gaseous nitrogen and nitrogen-containing surfactants as nitrogen precursors in aqueous environments. The performance of the obtained particles was investigated for the biosensing of proteins of bovine serum albumin of different concentrations across time intervals, with the lowest detection threshold of 0.001 μg/ml. In the next stage of this Ph.D. thesis, the author thoroughly demonstrates the synthesis and dispersion of liquid gallium micron-sized particles in a viscous organic reactant with minimised surface oxidation. The gallium dispersion was then reacted into a flexible polyurethane sponge composite with thermal and electrical conductivity, and also with strain-sensing capabilities. The mechanical, thermal and electrical properties of the composites were tuneable corresponding to the gallium content and dispersion. The pressure and temperature-dependent electrical resistivity were demonstrated from an electrical insulator state to a conductive behaviour with resistivity as low as 3.8 Ω m. In the final stage of this Ph.D. thesis, the author presents a straightforward pathway for the spontaneous synthesis of a full inorganic gallium-based liquid metal composite at room temperature. The micron-sized gallium particles synthesised via a low-energy sonication method were interconnected with inorganic manganese oxide nanostructures. By varying the manganese precursor concentrations and performing an annealing post-treatment, the morphologies and optoelectronic properties of the inorganic composites were finely controlled and demonstrated. Collectively, the studies presented in this Ph.D. research uncover novel pathways and mechanistic insights towards the sonication behaviours of liquid metals towards emerging and future applications