Sanni, Olutoba (2020) INFLUENCE OF POLYMER SURFACES ON BACTERIAL BIOFILM FORMATION. PhD thesis, University of Nottingham.

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High throughput materials discovery screens have revealed polymers that reduce bacterial surface colonization which have progressed to ongoing clinical trials [Hook et al. Nature Biotech 2012]. These novel poly(meth)acrylate coatings reduced biofilm formation by Pseudomonas aeruginosa, Staphylococcus aureus and Escherichia coli in laboratory cultures in vitro and in vivo in a mouse foreign body infection model. These coatings are known to function by preventing biofilm formation; however, why the bacterial cells respond in this way to these polymers has yet to be elucidated. This knowledge gap leaves us unable to undertake rational design of novel materials to prevent bacteria attachment. In this thesis, we focus on understanding the influence of the polymer surface on attachment of bacteria and subsequent biofilm formation.

Using ToF-SIMS and XPS, we carry out careful surface chemical analysis of adsorbates on two polymers known to exhibit drastically different biofilm formation in a standard biofilm promoting culture media: protein-free, amino acid containing bacterial RPMI. Amino acid adsorption is identified to correlate with polymer resisting biofilm formation. The amino acid adsorption process for these two polymers was modelled and two key descriptive parameters: adsorbent capacity and on/off rate of nutrients on polymer surfaces were obtained.

To move the study from a small set of samples to a greater number from which to derive a structure-function relationship, we developed a high throughput surface characterisation approach. A cheap ninhydrin staining technique, which allows to quantify by fluorescence amount of adsorbed amino acids from standard RPMI onto surfaces of individual polymers in a microarray in high throughput manner was adapted. The amount of adsorbed amino acid on individual polymers together with ion fragments obtained from ToF-SIMS were used to develop a linear regression model and identify key fragments that promoted nutrient adsorption using a total of 141 polymers chosen on the basis of possessing carbon, hydrogen and oxygen atoms.

To guide synthesis of novel anti-biofilm materials beyond the original monomer library, a simple predictive composite parameter termed alpha [Sanni et al. Adv Healthc Mater, 2015] that takes into consideration contributions from the partition coefficient (logP) and the number of rotatable bonds (nRotB) for hydrocarbon acrylate pendant groups was validated experimentally. We report the predictions of new monomers from the alpha QSAR model were successfully validated by the synthesis of new monomers, which were polymerized to create coatings found to be resistant to biofilm formation by six different bacteria pathogens: Pseudomonas aeruginosa, Proteus mirabilis, Enterococcus faecalis, Klebsiella pneumoniae, Escherichia coli and Staphylococcus aureus.

Potential biological degradation of novel anti-biofilm material has been postulated as a possible mode of action for these materials through release of bactericidal compounds. Here we used a quick-acting esterase enzyme (PLE) to verify that the mechanistic mode of action for novel anti-biofilm material was not due to enzymatic release of bacteriostatic/bactericidal compounds.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Alexander, Morgan
Williams, Paul
Irvine, Derek
Davies, Martyn
Keywords: biofilms, bacteria, polymer surfaces, bacterial biofilms, antibiofilm polymers
Subjects: Q Science > QD Chemistry > QD241 Organic chemistry
Q Science > QR Microbiology > QR 75 Bacteria. Cyanobacteria
Q Science > QR Microbiology > QR100 Microbial ecology
Faculties/Schools: UK Campuses > Faculty of Science > School of Pharmacy
Item ID: 60079
Depositing User: Sanni, Olutoba
Date Deposited: 11 Oct 2023 13:16
Last Modified: 11 Oct 2023 13:16

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