Quantification of bacterial growth within orthopaedic scaffolds and assessment of the efficacy of antibacterial surface treatments

Zurawski, Michal (2022) Quantification of bacterial growth within orthopaedic scaffolds and assessment of the efficacy of antibacterial surface treatments. PhD thesis, University of Nottingham.

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Abstract

This thesis reports on the development of quantifiable methods for the assessment of bacterial bioburden within three-dimensional orthopaedic scaffolds, and the subsequent investigation of the effects of exposure of their surfaces to proteins has on the observed biofouling. The lack of readily available methods for this purpose, and the rising cost (both human and financial) of biofilm infection of orthopaedic devices prompted the need for this research.

Existing methods are identified during the literature review, such as Confocal Laser Scanning Microscopy (CLSM) and Micro-CT which are used in the research field are first investigated for efficacy as they have been used in some studies.

The aim of this study is to develop and validate a new analysis method to provide quantifiable, accurate and reliable results for the measurement of bacterial biofouling on flat and three-dimensional samples alike. This method is then used to measure the bacterial biofouling of samples once inoculated and incubated with S. aureus in a protein-rich environment they would be exposed to in situ inside a patient.

Analysis using SEM micrographs is adopted as a methodology and refined in this work. The standardised approach which takes readings in triplicate from each sample, and measures bacterial surface coverage of the imaged area through computational image analysis is used to study commercially-available orthopaedic scaffolds (Ta and Ti6Al4V), as well as samples containing elements known for their antibacterial properties (Cu and I).

The reliability of the novel SEM methodology is shown through validation against the research standard of CLSM, which is readily used for analysis of flat, two-dimensional samples. Once validated, the SEM methodology is then used to study the effect a surface which has been pre-conditioned with protein has on bacterial biofouling compared to a clean surface, both when the substrate surface chemistry has known antibacterial properties or not. It is found that the physical shielding of bacterial cells from the antibacterial surface agent by the protein film reduces the antibacterial effect.

The new method developed is of significance as it provides researchers a reliable way to measure biofouling in three-dimensional structures with a protocol made for that very purpose. It is hoped that this method will continue to be refined to further enable research within microbiological assessments within orthopaedic scaffolds which carry a risk of biofilm infection in a clinical setting. The protein conditioning studies go on to explain why samples, even when containing known antibacterial agents, are still susceptible to bacterial infection in a clinical setting.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Grant, David
Scotchford, Colin
Atkinson, Steve
Felfel, Reda
Keywords: Biofilms; Orthopedic apparatus; Orthopedic implants; Fouling
Subjects: Q Science > QR Microbiology > QR100 Microbial ecology
R Medicine > RD Surgery
Faculties/Schools: UK Campuses > Faculty of Engineering
Item ID: 68277
Depositing User: Zurawski, Michal
Date Deposited: 31 Jul 2022 04:41
Last Modified: 31 Jul 2022 04:41
URI: http://eprints.nottingham.ac.uk/id/eprint/68277

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