| dc.description.abstract | Self-assembling building blocks based on peptides have attracted great interest in tissue engineering due their intrinsic bioactivity. Supramolecular peptide-polymer assemblies have advantage of mimicking the natural protein-polymer complexes present in biological systems. Hyaluronic acid (HA) is an anionic, non-sulfated glycosaminoglycan involved in varied and essential biological activities, which is also one of chief components of the extracellular matrix (ECM) of tissues and the human vitreous. This thesis presents the fabrication of novel supramolecular hydrogels containing polyelectrolytes and rationally designed peptides and the exploitation of peptide-HA hydrogels as in vitro models. In Chapter 1 the research background of the project is introduced. It starts with a short review on self-assembling peptides and their hydrogel formation, followed by an overview about the HA macromolecule, and then finalised by discussing the research done on hybrid supramolecular peptide-polymer complexes. The objectives of the work described in the thesis are provided. Chapter 2 describes in detail the materials and methods used in the project and in the work described in the following chapters (3, 4 and 5). The design, synthesis and characterization of novel self-assembling cationic peptides [(KI)nK] are described in Chapter 3, where the number (n) of repeating unit (lysine-isoleucine) varies from two to six. Peptides are found to behave as random coils at neutral pH, but form β-sheet rich fibrous nanostructures at basic pH. Several polyelectrolytes (HA, alginate, poly(styrene sulfonate and poly(acrylic acid)) are used to construct supramolecular peptide-polyelectrolyte hydrogel complexes, whereby the negative charge of the polyelectrolytes are used to screen the positive charges present on the peptides. The microstructures and mechanical properties of the peptide-polymer hydrogels are investigated in detail to identify hydrogel candidates for biomedical applications. Chapter 4 focuses on the supramolecular peptide-HA hydrogels. This chapter describes the possibility of tuning the mechanical properties and morphology of peptide-HA hydrogels by changing the concentration of the components and the peptide sequence. In addition, the kinetic of the peptide-HA hydrogel formation, the hydrogel degradation in presence of hyaluronidase and its alignment under shear strain are also investigated. Chapter 5 investigates the in vitro application of the supramolecular peptide-HA hydrogels, including their use as vitreous model and as platform for stem cell culture. HA is an essential polysaccharide of the ECM mediating activities in cellular signalling, wound repair, morphogenesis and matrix organization, and the supramolecular peptide-HA hydrogel provides a simple strategy to fabricate a synthetic ECM without chemical modification. It is found that human mesenchymal stem cells can form spheroids on peptide-HA hydrogels. The cell behaviour on peptide-alginate hydrogel and peptide-polymer coated surfaces, used as controls, was investigated to understand mechanism for the spheroid formation. Chapter 6 summarizes the main findings reported in this thesis and suggests ideas for further investigation. As shown in the previous chapters, the peptide-polyelectrolyte complexes, in particular (KI)nK-HA hydrogels, offer an opportunity to recapitulate the nanostructure and biofunction of the native ECMs, while enabling fine adjustments of their mechanical properties. While some potential biomedical applications of the peptide-HA hydrogels were exploited in this project, further applications are outlined in the final chapter, such as artificial substrate supporting neural differential and in vitro tumour models. | en_US |
