Thesis

Aromatic peptide amphiphiles : design rules for hydrogelaion and co-assembly

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Awarding institution
  • University of Strathclyde
Date of award
  • 2014
Thesis identifier
  • T13740
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Department, School or Faculty
Abstract
  • The overall objective of this thesis was to elucidate molecular design rules for the preparation of self-assembled aromatic peptide amphiphile based hydrogels. Aromatic peptide amphiphiles can be considered as having three distinct parts: the N-terminal aromatic group, peptide sequence, and the linker between the two. A systematic variation of these three molecular components has in the first instance revealed that contrary to popular belief, the antiparallel or parallel H-bonding supramolecular conformations associated with aromatic peptide amphiphiles cannot be distinguished by FTIR experiments alone. Instead, the 1685 cm-1 peak commonly assigned to an antiparallel arrangement, relates to the methoxycarbonyl linker if present in these systems. The choice of linker is also seen to have implications for assembly in both the aromatic and peptidic domains - as seen by fluorescence emission and FTIR respectively. In addition, the linker influences the supramolecular chirality of the fibrous nanostructures by CD. The optimal linker for effective self-assembly and gelation is observed to depend primarily on the corresponding aromatic moiety, with fluorenyl and pyrenyl systems exhibiting differential preferences for relatively rigid and relatively flexible linkers, respectively. Besides covalent alterations, aromatic peptide amphiphile materials can also be modified through co-assembly. Here, the co-assembly structure is found to vary depending upon the aromatic and peptide segments associated with co-assembly constituents. Orthogonal co-assembly is observed in systems with different aromatic and peptide parts, as inferred by a preservation of characteristic spectroscopy and material properties associated with the assembly of individual constituents. In contrast, nanoscale phase separation is found to be disfavoured in systems that share either a common aromatic or peptide segment between co-assembly constituents. Consequently, for cooperative and disruptive systems, spectroscopy reveals substantial interactions between constituents, whilst material properties are also found to be affected through co-assembly. Finally, preliminary work demonstrates the functionalisation of bulk electrodes and MEA devices with electrochemically deposited hydrogel coatings possessing an electronic core furnished with a biocompatible coating as derived from the aforementioned co-assembly design rules. Coated electrodes are found to exhibit similar impedances to those of uncoated nodes, but prove inferior to platinised equivalents. Future work will focus on optimising said electrode impedances for potential neuron-device interface applications.
Resource Type
DOI
Date Created
  • 2014
Former identifier
  • 1032616

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