| Summary: | As understanding of host immune responses towards implanted biomaterials has grown, macrophages have been identified as critical predictors of inflammatory consequences following implantation. Depending on the phenotype they adopt in response to biomaterials in vivo, different macrophage phenotypes can either perpetuate chronic inflammation (via M1) or promote tissue healing (via M2). In the setting of tissue repair, a prompt shift in macrophage polarisation from a proinflammatory (M1 macrophages) to an anti-inflammatory (M2 macrophages) favours enhanced healing. In some cases, patients suffer adverse immune reactions to implanted devices leading to chronic inflammation, pain, and on occasion, implant failure. Therefore, it is beneficial to have an in-depth understanding of the metabolomics of different macrophage phenotypes, as this would help understand and improve the response of the human body to biomaterials.
Characterization of the small molecule signature, the metabolome of macrophage subsets within individual cells (in vitro) and tissue sections (ex vivo) offers great potential to understand the response of the human immune system to implanted biomaterials. As a first in vitro step I investigate the possibility of using 3D OrbiSIMS to characterise the metabolic profile of single cells after cytokine differentiation into naïve (non-polarised), M1 and M2. I identify key characteristic metabolites for each macrophage subset (Chapter 4). In the second step, I used of methacrylate monomers to synthesise copolymers via a thermal polymerization method and subsequently coat coverslips. Moreover, I found the coated polymers to impact on macrophage polarisation in terms of their behaviour and phenotype of macrophages (Chapter 5). In the third step in vivo, I investigate explanted as purchased and polymer coated silicon catheter coated sections as a model medical device in a subcutaneous rodent model of foreign body response (Chapter 6). Here, I identified the bio-instructive polymer coatings to induce macrophage pro/anti-inflammatory responses in vivo by examining the tissue surrounding the foreign body site from mice using immunohistochemistry, staining and using the 3D OrbiSIMS specifically employing a gas cluster ion beam (GCIB) and an Orbitrap analyser.
In summary, findings from this study show the potential of metabolomic analysis by 3D OrbiSIMS to achieve unbiased insight into cellular phenotype at the resolution of a single cell in culture. Also, this is possible on explanted devices in order to their response to various biomaterials.
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