Davrandi, Mehmet Kerem; (2020) Development of an in-vitro biofilm model for the investigation of dental plaque biofilms. Doctoral thesis (Ph.D), UCL (University College London).

Text MD_Thesis_Final_July2020.pdf - Accepted Version Access restricted to UCL open access staff until 1 August 2025. Download (143MB)

Abstract

The oral cavity is an open ecosystem housing a diverse range of microorganisms. In-vitro modelling enables investigation of this complex microbial ecosystem under controlled environmental conditions and also provides a tool for development of oral hygiene strategies. Given all biofilm model systems have their advantages and drawbacks, the aim of this PhD project was to develop a new biofilm model system capable of generating steady-state oral biofilms with representative microbial community under varying nutrient conditions. In the first part of this project, I explicitly focused on model development starting with the evaluation of the MBEC Assay system. In chapters 3 and 4, a range of growth media formulations and two feeding regimes were tested and it was concluded that the MBEC Assay system had major design drawbacks for the purpose of this study. Therefore, we designed a new biofilm model system (the Eastman Device), and introduced a two-phased approach that included baseline biofilm formation followed by subsequent maturation. Ultimately, the Eastman Device combined with the final experimental protocol was able to generate steady state dental plaque biofilms that were compositionally and physiologically comparable to that of the in-vivo biofilm. In the second part, I investigated the effect of two growth media on biofilm maturation by means of community and EPS matrix composition and used the system to examine the response to a CPC containing mouthwash. The community profiles were similar between the two growth media but eDNA content was significantly higher in the artificial saliva grown biofilms, and the same was true for total protein and NaOH-soluble polysaccharide in the modified brain heart infusion grown biofilms. Despite these differences, both mature biofilm types were found to be equally resilient to the mouthwash treatment, which showed no beneficiary effect throughout five days. Collectively, the findings demonstrated that the new model, and the experimental protocol generated a convenient tool for oral biofilm research with its parallelisable high-throughput capability and reproducibility.

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