Magnetic reconance imaging characterization of porous substrates and models of soil and biofilms

Cimmarusti, Gabriele Michele ORCID: 0000-0002-7030-2915 (2022). Magnetic reconance imaging characterization of porous substrates and models of soil and biofilms. University of Birmingham. Ph.D.

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Abstract

Bacteria and biofilms are frequently found growing in sponges and are a common cause of malodour in the sponge and cross-contamination of humans and surfaces with the risk of causing bacterial infections. Bacterial infection generates high annual healthcare costs and are related to high mortality rates. Removal of bacteria and biofilms from sponges is thus of critical importance to avoid infections, food poisoning, and surface contamination. To tackle biofilm development in sponges, and thus reduce cross contamination, fast-moving consumer goods (FMCGs) companies have focused on developing detergents which can remove food from sponges. However, due to their intrinsic method’s limitation, current existing techniques, such as X-Ray micro-CT, confocal laser scanning microscopy, scanning and transmission electron microscopy, do not allow a complete understanding and visualization on how detergents act in removing food and biofilms from sponges. To fulfil this gap, new methodologies need to be developed to increase knowledge on biofilm development, particularly within sponges, and its relationship with food residues, as well as on fluid dynamics within sponges. Thanks to their nature, nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) could allow to image food residues and biofilm development in porous media in-situ and in-vivo. Moreover, NRM and MRI enable the characterization of the 3D internal structure of porous media and the visualization of fluid flow within them. Thus, NMR and MRI could potentially allow to study how the physical parameters of sponges affect fluid flow, and how this is related to food residues removal and biofilm development in sponges, in-situ and without the need of pre-treatments.

In this work, novel nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) have been developed to characterize polyurethane open-cell porous media, and directly visualize food and biofilms within, without the need of sample pre-treatment or the addition of contrast agents. A combination of NMR relaxometry, MRI T2 relaxation maps and X-ray micro computed tomography (µCT), has highlighted the dependence of T2 relaxation times of water, within the foam, on the pore sizes. This has enabled the creation of new protocols to characterize polymeric open-cell porous media directly by MRI, which can be combined with MRI visualization of composition and flow. MRI Chemical Shift Selective (CHESS) imaging has been employed to visualize food residues within polyurethane (PU) sponges, enabling the selective mapping of hydrophobic and hydrophilic residues within the sponge without additional contrast agent. Finally, MRI chemical exchange saturation transfer (CEST) experiments have been successfully developed to image polysaccharide-based (alginate) materials within sponges, demonstrating their potential to visualise the exopolysaccharide matrix of biofilms without the need for additional contrast agents.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):