| The use of beta-sheets as building blocks for biomaterials is already firmly established. In particular, self-assembled beta-sheet peptides are promising for engineering new fibrous nanostructures and hydrogels. Peptide-synthetic polymer hybrids are especially attractive since they combine the advantages of biomolecular recognition and functional properties of peptides with the low cost and easy fabrication of polymers. Significant developments in the area have included beta-sheet fibrillar networks, and self-assembled hybrid hydrogels, which add further control and utility to these systems. The studies described in this dissertation dealt with the design and evaluation of novel nanofibrous and hydrogel materials based on poly(HPMA)-beta-sheet copolymers and their application as scaffolds for bone tissue engineering. In the first part of this research, the effect of conjugating poly(HPMA) to a beta-sheet peptide via thiol-maleimide chemistry was estimated. The ability of the peptide to adopt a beta-sheet conformation could be imposed in the hybrid at basic pH, through electrostatic interactions between the oppositely charged amino acid residues in the sequence. Hierarchically organized structures, such as micrometer long fibrils, were obtained. In the second part, formation of fibril-like nanostructures was demonstrated for beta-sheet peptides conjugated as grafts to poly(HPMA). The polymer had a shielding effect, decreasing the peptide grafts sensitivity to temperature and pH variations. The tendency of beta-sheets to form hydrogels was preserved in the copolymer depending on the concentration, graft density, and incubation time. Finally, the last part of this research attempted to explore the ability of a hybrid hydrogel self-assembled from copolymers of poly(HPMA) and complementary beta-sheet grafts to act as scaffolds for bone tissue engineering. The hydrogel displayed anisotropic porosity, thus, it provided surfaces characterized by epitaxy that favored template-driven mineralization of hydroxyapatite, and support for preosteoblast cells. Although attachment did not occur, long-term viability of cells and proliferation indicated that the hybrid hydrogel is not cytotoxic, therefore, once optimized, could be used as a bone scaffold. In summary, we have presented novel beta-sheet-based hybrid nanostructures and hydrogels that could be applied successfully in regenerative medicine. Such an approach may lead to the development of new materials for drug delivery, wound healing or other tissue engineering applications. |
