Design of polymer coated magnetic nanoparticles for the selective isolation of bacteria from mixed populations

Petch, Joshua Edward (2020) Design of polymer coated magnetic nanoparticles for the selective isolation of bacteria from mixed populations. PhD thesis, University of Nottingham.

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Abstract

The ability to selectively sequester bacteria from a mixed population is a desirable aim across a range of fields. Already some technologies exist to attempt to meet these aims however, these are generally limited to the confinement of small populations in defined locations and may be unable to differentiate between morphologically similar but phenotypically distinct cells. Furthermore, the use of immunomagnetic nanomaterials is likely to be prohibitively expensive for many scaled-up applications.

Magnetic glyconanoparticles (MGNPs) as a platform for specific bacterial capture by lectin-mediated attachment appear promising but have yet to be utilised for the extraction of bacteria from mixed populations. The work described in this thesis attempted to address this shortcoming.

An inducible mutant of the Type 1 fimbriae, a mannose-specific lectin, was produced in a wildtype E. coli background via a homologous recombination strategy. Binding to glycopolymers was only observed in the presence of the inducer and was specific for mannosylated but not galactosylated glycopolymers.

Well-defined glycopolymers of mannose and galactose acrylamides of varying chain length were synthesised by RAFT polymerisation with a dopamine terminal chain transfer agent and polymerisation kinetics was investigated. Binding studies revealed a complex relationship between lectin avidity and glycopolymer chain length. The dopamine functionality of these glycomaterials allowed for facile functionalisation of superparamagnetic iron oxide nanoparticles with glycopolymers and lectin affinity was retained upon particle decoration.

Delivery of these glycopolymer-decorated nanoparticles to co cultures of fluorescently labelled bacteria facilitated efficient depletion of Type 1 fimbriated target cells from wildtype or afimbriate E. coli. Extraction efficiency of fimbriated E. coli was improved when the counterpart strain did not harbour the genetic apparatus for expression of the Type 1 fimbriae. However, release of the captured cells from the nanoparticles by addition of a monovalent competitive ligand could not be adequately demonstrated under the tested conditions.

Overall this work suggests that MGNPs may prove a versatile tool for the extraction of bacteria from mixed populations based on the sugar-binding preferences of different bacteria or control over the genetic apparatus encoding bacterial surface associated lectins. However, additional investigation is required to fully investigate the limitations of this system.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Mantovani, Giuseppe
Camara, Miguel
Heeb, Stephan
Keywords: Bacteria; Magnetic glyconanoparticles; Bacteria extraction; Surface-associated lectins
Subjects: Q Science > QR Microbiology > QR 75 Bacteria. Cyanobacteria
Faculties/Schools: UK Campuses > Faculty of Science > School of Pharmacy
Item ID: 59973
Depositing User: Petch, Joshua
Date Deposited: 16 Jul 2020 04:40
Last Modified: 16 Jul 2020 04:40
URI: http://eprints.nottingham.ac.uk/id/eprint/59973

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