Primary Supervisor: Dr Sarah Kuehne, School of Dentistry
Secondary supervisor: Dr Sophie Cox (UoB) & Dr Richard Shelton (UoB)
PhD project title: Development of a co-culture system to improve pre-clinical dental implant testing
University of Registration: University of Birmingham
Background: In the US alone about 1.3–2 million dental implants are placed annually (Achermann & Day, 2012). Once in place, the race to the surface starts (Gristina AG, 1987; figure 1). Tissue cells grow and integrate the new material in a process known as osseointegration. At the same time bacteria, present in the oral cavity, start to adhere to the new surface. The mouth is a non-sterile site. It is colonised by thousands of microbes, mostly living in biofilms. The healthy mouth represents an equilibrium of microbes and host cells, but this can be disturbed shifting the balance to a disease-associated biofilm. New implants are at risk of implant failure due to infection and inflammation. The concept of the race to the surface is not new and novel materials and antimicrobial approaches are being developed all the time, but we are still lacking sufficiently representative model systems to test these adequately. It is critical that we are able to test developing implants and biomaterials in physiological relevant environments. Therefore, we have now developed a preliminary 3-D organotypic cell culture model, which encompasses a capacity for integration of materials to be tested and bacterial challenge. The project will focus on refining this model through rigorous testing in order to provide the biomaterials field with a robust pre-clinical asset that may support the progression of new implants.
Aim: Refinement and evaluation of a 3D model consisting of a hydrogel containing fibroblasts and epithelial cells (representing the mucosa/gum) being exposed to oral bacteria (single and mixed species biofilms) in an in vitro model modified from Millhouse et al (2014). Exploration of addition of a calcium phosphate scaffold containing osteoblasts (representing bone) encased by the above-mentioned hydrogel to develop an even more realistic model.
Further evaluation of this model to study osseointegration and risk of infection/inflammation through ‘implanting’ of various biomaterials. Biological and physical optimisation of the 3D model will be performed iteratively.
Methodology: This project will combine biological (eukaryotic cell biology and microbiology) with physical lab-based techniques to develop a novel 3D-implant model. We will (1) build on our present model combining fibroblasts in a hydrogel support covered by an epithelial layer (potentially encasing a porous hydroxyapatite disc), which will be exposed to a biofilm of Streptococci (early colonisers of oral biofilms) in a cell-culture insert set-up (figure 2). Cell proliferation, viability and bacterial growth will be measured (2) using established assays and confocal microscopy including live-dead staining and analysis with Image J.
Scientific outcomes: Development of a new 3D-implant model which will be used to study (dental) implants (different topographies, antimicrobial approaches), with particular emphasis on the interplay between mammalian and bacterial cells.
- Achermann, How will dentistry look in 2020?, Straumann CMD, 2012.
- G. Gristina, Science, 1987, 237, 1588.
- Millhouse et al, BMC Oral Health, 2014, 14, 80.
BBSRC Strategic Research Priority: Understanding the Rules of Life: Microbiology
Techniques that will be undertaken during the project:
- Physical sciences:
- Formulation of biomaterials, in particular hydrogels and hydroxyapatite. Characterisation of biomaterials: rheology and mechanical testing.
- Comparison of mechanical properties of human tissue to model
- Biomedical sciences:
- Culture of mammalian and bacteria cells.
- Biological assays to assess cell growth, proliferation, adhesion, bacterial-cell interactions.
- Cytokine assays
- Biofilm growth, evaluation including biomass, live/dead staining, confocal microscopy (imaging and image analysis)
Contact: Dr Sarah Kuehne, University of Birmingham