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Title: Functional protein-polymer surfactant hybrid nanomaterials
Author: Yixiong , Zhang
ISNI:       0000 0004 5915 2180
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2014
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This thesis presents the investigation of protein-polymer surfactant hybrid nanoconstructs prepared through the surface modification of haemoglobin (Hb) or glucose oxidase (GOx). These discrete stoichiometric conjugates of protein and polymer (with respect to charge) exhibited liquid-like behaviour close to room temperature in absence of solvents. Solvent-free Hb nanoconstructs could be readily dispersed into various organic solvents to form stable molecular protein-polymer surfactant conjugates. Spectroscopic studies showed that surface modification effectively protected the secondary structures of Hb from denaturing under non-aqueous conditions. Importantly, Hb-polymer surfactant conjugates displayed significantly enhanced peroxidase activity in organic solvents compared to their native counterparts, suggesting the polymer surfactant corona successfully shielded the enzyme-bound water layer and increased the protein's functional dynamics for non-aqueous catalysis. Solvent-free GOx nanoconstructs showed unprecedented phase behaviour because of the shape anisotropy of the protein. Below the melting point (40°C), the nanoconstructs exhibited spherulitic mesolamellar structures with an interlayer distance of "'12 nm due to the polyethylene glycol (PEG) chain-chain and alkyl tail-tail interactions within the polymer surfactants of the nanoconjugates. Upon melting, the spherulites transformed into a solvent-free liquid which displayed another PEG-mediated anisotropic phase with dendritic morphology that persisted until the conformation transition temperature (Te) of GOx (58°C). This suggested that the change in intra-polypeptide motions of the protein core during Te significantly influenced the intermolecular interactions of the solvents-free GOx-polymer nanoconjugates. With retained enzymatic activity, GOx-polymer surfactant nanoconjugates were effectively immobilized onto a porous membrane to serve as reusable biocatalysts. The resultant fabricated enzyme-based membrane exhibited greatly improved catalytic efficiency for oxidation of D-glucose. Moreover, incorporation of this enzyme membrane into a glucose-based hydrogel provided a constant release of oxygen (in the form of hydrogen peroxide) over a long period of time, which could offer new opportunities in the development of dressing for wound healing.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available