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Photodynamic high-level disinfection for medical surfaces

Pascoe, Michael J. 2019. Photodynamic high-level disinfection for medical surfaces. PhD Thesis, Cardiff University.
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Abstract

This project sought to evaluate photosensitisers as feasible alternatives to traditional biocide products for disinfecting medical surfaces. Photosensitisers produce damaging reactive oxygen species in the presence of light and may be safer than traditional disinfectants. However, their biocidal efficacy has yet to be determined using standardised methods and so comparisons with current technology are not possible. After establishing the photosensitiser toluidine blue O (TBO) as a lead compound, a biocide formulation was developed which exhibited broad spectrum bactericidal activity against a range of bacterial species. In the following chapter, the effect of photosensitiser-treatment on target cells was established and was observed to target the bacterial cytoplasmic membrane and nucleic acids. Upon testing against a broad spectrum of challenge organisms, the formulation was highly biocidal against yeasts, non-enveloped viruses and fast-growing mycobacteria and moderately effective against bacterial biofilms. However, its biocidal activity was found lacking against Aspergillus conidia, slow-growing mycobacteria and bacterial endospores. Further investigation determined that pigments, permeability barriers and DNA protection mechanisms confer resistance to photosensitisation. Evaluation of the scalability of photosensitiser-based disinfection determined that photosensitisers boast an exceptional ecotoxicological profile and can be produced at a price comparable to other disinfectants. Whilst photosensitisers are yet to be registered as an active substance in the European Union, they fulfil the general requirements of registration and do not contradict any exclusion criteria. Incorporating photosensitiser-based disinfection technology into complex devices such as an automated endoscope reprocessors is feasible, though would require complex design considerations which may discourage its use. Overall, these data demonstrate that photosensitiser-based biocide formulations are insufficiently effective for high-level disinfection of medical surfaces. However, their low production costs and ecotoxicological properties may make them suitable for alternative applications. The technology can be readily scaled-up the disinfection of commercial food preparation surfaces and so further investigations into alternative uses are recommended.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Pharmacy
Subjects: Q Science > Q Science (General)
Date of First Compliant Deposit: 8 April 2020
Last Modified: 29 Mar 2021 15:29
URI: https://orca.cardiff.ac.uk/id/eprint/130149

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