Design and characterisation of polyhydroxyalkanoate bead-alginate hybrid materials : a dissertation presented in partial fulfilment of the requirements of the degree of Master of Science in Microbiology at Massey University, Manawatū, New Zealand
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Date
2018
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Massey University
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Abstract
Encapsulation is a technique to entrap a material of interest within a carrier material, and
it has been used in a wide range of industries such as biopharmaceutical and
biotechnological companies. Among biopolymers used for the carrier material, alginate
has been widely used due to its attractive properties of biodegradability, biocompatibility
and ease of gelation under mild conditions. In this study, a novel hybrid micro- or millisphere
composed of functionalised polyhydroxyalkanoate (PHA) beads and alginate was
fabricated through ionotropic gelation methods. The selected functional proteins
displayed on PHA beads were the IgG binding domain (ZZ) of Protein A from
Staphylococcus aureus, and organophosphate hydrolase (OpdA). The effect of alginate
encapsulation on their functionality was assessed. In addition, alginate millispheres
encapsulating PHA beads were assessed for their ability to remove lipophilic compounds
from an aqueous solution. This utilised the hydrophobic polyester core of the PHA beads
and was assessed by using the lipophilic dye, Nile red, as the reporter.
The results of IgG binding assays using PHA beads encapsulated in alginate microspheres
showed no significant difference compared with negative controls, and no elution of
bound IgG was observed. However, the alginate encapsulation enhanced IgG binding to
the PhaC derived proteins on PHA beads within alginate microspheres. In contrast,
alginate encapsulation limited the activity of PHA beads displaying OpdA when
compared to free PHA beads. The qualitative data obtained from phase contrast and
fluorescence microscopy suggested that the enzyme displayed on PHA beads was active
within alginate microspheres. The lipophilic dye removal by PHA beads encapsulated in
alginate millispheres was influenced by different parameters used in the millisphere
preparation. The adsorption kinetics aligned with a pseudo second-order kinetic model,
and the equilibrium adsorption data was in agreement with the Freundlich isotherm model.
This study has provided preliminary data for fabrication of a hybrid material of
functionalised PHA beads with alginate. The development of combinations of highly
functional PHA beads with other biomaterials is expected to expand the application field
of PHA beads.
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Keywords
Microencapsulation, Alginates, Biopolymers