The effect of conditioning films on the hygienic status of titanium based and antimicrobial surfaces

Tetlow, Louise Ann (2018) The effect of conditioning films on the hygienic status of titanium based and antimicrobial surfaces. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Biofouling and contamination of surfaces is of critical importance to both the food and medical industries, causing not only huge economic burden, but also increased health risks to consumers and patients. The choice of surfaces which can help mitigate these risks is of critical importance. Antimicrobial surfaces were developed through unbalanced magnetron sputtering was producing titanium nitride and silver surfaces (Ag content = 15.03 % 25.45 %) which were to be assessed alongside surfaces commonly utilised in both medical and food industries; 3042R and 316L stainless steel, titanium, 316Ti, 316TiN. The surfaces were assessed for their physical and chemical properties through the use of SEM, EDX, goniometry, FTIR-DRIFTS, WLP and through comparisons with the pristine surfaces (control), assessment of what changes the addition of the bacterial species Staphylococcus aureus and Escherichia coli, 10 % bovine plasma conditioning film, or both the bacteria and conditioning film made to those parameters. The antimicrobial properties of the surfaces and their propensity to retain the bacterial species was also measured through ZOI, NTV and retention assays, as well as assessment of what effect the addition of the conditioning film upon the surfaces had upon bacterial retention. Results demonstrated the addition of the conditioning film made no significant difference to the physical properties of the surfaces but did affect the chemical properties. Assessment of the antimicrobial properties of the surfaces demonstrated that only the TiN/Ag surfaces were antimicrobial and that the bacterial response was species specific. Retention assays demonstrated that upon the pristine surfaces the E. coli was influenced by the physicochemistry of the surfaces, whilst the S. aureus was influenced by the surface topography. The conditioning film produced a significant reduction in the numbers retain bacteria to the surfaces. In conclusion, the bacteria were more significantly affected by the presence of the conditioning film than the physical parameters of the surfaces. This result was mediated by the affects that the conditioning film had upon the chemical parameters of the surfaces in conjunction with the molecular effects of protein binding to surface adhesins. This work demonstrates that whilst characterisation of the surface parameters is important, this must also be done in the presence of an appropriate conditioning film.