Dynamic supramolecular hydrogels with adaptive biological functionality

  • Yousef Abul-Haija

Student thesis: Doctoral Thesis

Abstract

Molecular self-assembly coupled with (bio)catalysis underlie dynamic processes in biology and are considered as powerful tools for fabricating adaptive materials. In nature, the extracellular matrix (ECM) - the complex yet dynamic environment surrounding cells, provides cell support and ultimately determines cell fate. Cell behaviour depends on three main ECM properties; (i) its biochemistry presented by the chemical functionality exposed to the cells, (ii) its (nanoscale) topography and (iii) its mechanical properties (i.e. stiffness). The ultimate goal of this research is to develop materials that could mimic the ECM properties and function with minimal complexity by combining self-assembly and biocatalysis. Aromatic peptide amphiphiles and aromatic sugar amphiphiles are particularly interesting building blocks in this context and were mainly utilised in this work. For the development of applications and novel uses for peptide nanostructures, robust routes for their surface functi onalization, that ideally do not interfere with their self-assembly properties, are required. Many existing methods rely on covalent functionalization, where building blocks are appended with functional groups, either pre- or post-assembly. In the first part of this thesis, we demonstrate a facile supramolecular approach for the formation of functionalized nanofibers by combining the advantages of biocatalytic self-assembly and surfactant/gelator co-assembly. This is achieved by enzymatically triggered reconfiguration of free flowing micellar aggregates of pre-gelators and functional surfactants to form nanofibers that incorporate and display the surfactants’ functionality at the surface. Furthermore, by varying enzyme concentration, the gel stiffness and supramolecular organization of building blocks can be varied. Then, a non-enzymatically triggered peptide-based hydrogelator was co-assembled with different amino acid and simple sugar based surfactant-like functionality. Wecompete and selectively deco mpose, enabled by biological catalysis. In the final part of this thesis, we describe a synthetic mimic by combining (i) peptide self-assembly, (ii) catalytic sequence exchange, (iii) peptide/polymer co-assembly in one system. Thus, we use coupled biocatalytic peptide condensation and self-assembly to achieve reversible and continuous exchange of peptide sequences and by incorporating charged residues, achieve selective amplification in the presence of cationic (chitosan) or anionic (heparin) biomacromolecules. We show that morphologically different peptide/polymer structures (nanotubes or nanosheets) can be competitively or sequentially accessed at physiological conditions.
Date of Award14 Jul 2015
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SupervisorRein Ulijn (Supervisor) & Peter Skabara (Supervisor)

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