AbstractThe process of forming supramolecular hydrogels through the assembly of gelators into high-aspect ratio nanofilaments is heavily kinetically dependent. Furthermore, the assembly process is highly sensitive to conditions such as ionic strength and temperature. Therefore, the process and environment in which self-assembly occurs can considerably alter the structures formed and the subsequent macroscopic properties of the hydrogel. Thus, investigations into novel stimuli and the effect on hydrogel properties are warranted.
The first experimental chapter of the thesis demonstrates the use of nitric oxide radicals for the dephosphorylation of the N-fluorenylmethyloxycarbonyl tyrosine phosphate (FYP) to form N-fluorenylmethyloxycarbonyl tyrosine (FY) gelator molecules. This novel stimulus resulted in filaments with a reversed supramolecular chirality, compared to filaments form through enzymatic cleavage of FYP.
The second chapter of the work highlights the design and construction of a nucleotide-amino acid multicomponent hydrogel. This is achieved through the addition of an inorganic stimulus, silver ions, to guanosine monophosphate (GMP) N-fluorenylmethyloxycarbonyl tyrosine (FY) solution. This exploits the association between silver and the guanine residue of GMP to form Ag-GMP dimers via an enolate tautomer and subsequent abstraction of a proton. The subsequent drop in pH can then triggers the gelation of the second gelator, FY. The ratio of Ag:GMP affects the assembly kinetics, the supramolecular organisation and the mechanical properties of the hydrogel. Higher stoichiometries result in rapid gelation and non-orthogonal assembly. However, at lower stoichiometries, this disruptive assembly is avoided, and FY filaments can be selectively disassembled through the raising of pH.
The final chapter investigates the potential of a nucleotide-based hydrogel as an antimicrobial agent. The antibacterial properties of this gel were characterised using a series of microbiological techniques. Significantly, the gel demonstrated substantial killing of gram-negative bacteria (E. coli) and gram-positive bacteria (E. faecalis). Gel electrophoresis experiments indicated that this activity seems to be, in part, due to damage caused to the chromosomal DNA.
|Date of Award||23 Jan 2019|
|Supervisor||Natasa Vasiljevic (Supervisor) & Avinash J Patil (Supervisor)|