Functionalised dipeptides as hydrogelators for energy transfer and as drug delivery vehicles

• Main Author: Awhida, Salmah
• Published: University of Liverpool 2015
• Subjects: 540
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.664445

This thesis will cover aspects of functionalised dipeptide hydrogels and their application in energy transfer and as vehicles for drug delivery. In the first section, a large number of dipeptides conjugated to different aromatic groups were synthesised. We synthesised 35 dipeptides conjugated to different aromatic groups (naphthalene, anthracene, phenanthrol, anthraquinone, carbazole and pyrene). We synthesised a large number of dipeptides with different hydrophobicity and different aromatic groups in order to study their ability to form gels and study the mechanical properties of the gels. The second part of this thesis will investigate the formation of hydrogels based on dipeptides with different aromatic groups. The focus in this section was on the gelation as well as the effect of changing the solvent and changing the amino acids used. This section then explores the properties of the resulting hydrogels. A number of different dipeptides containing different amino acids were tested, some of which formed gels and others. The dipeptides also had different pKa values. This factor was shown to be important in driving the preferential selection of a certain amino acids. The thesis then describes energy transfer which can occur between two dipeptides (pyrene and anthracene dipeptides), or between a dipeptide and a dansyl derivative (phenanthrol and dansyl, or carbazole and dansyl). These results showed that energy transfers can occur in these specific hydrogels. In all other cases, no evidence for energy transfer was found. This may imply that the packing of the fibres is important for energy transfer and this should be the focus of future work. The final section of this thesis describes the controlled release of model dyes from these gels. We studied controlled release from FmocFF hydrogels and from one other functionalised dipeptide hydrogel at different gelator concentrations and at different pH. The release of the dye from the hydrogel can be controlled by different factors, including the pH, peptide concentration, the microstructure and the mesh size. Furthermore, choosing the right method to prepare hydrogel allows us to control the microstructure for hydrogel to be injectable. Therefore, by controlling these entire factors we can use these kinds of hydrogels for drug delivery applications.