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Title: Spherical sub-micron bioactive glass particles and their interaction with cells in vitro
Author: Labbaf, Sheyda
ISNI:       0000 0004 2713 4519
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2011
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Sub-micron bioactive glass particles (SMBGs) with composition 85 mol% SiO2 and 15 mol% CaO were synthesised and characterised. Bioactivity was demonstrated by the formation of calcium apatite following 5 days immersion in simulated body fluid (SBF). The effect of a 24 h exposure of human mesenchymal stem cells (hMSCs) to SMBGs at concentrations of 100, 150 and 200 μgml-1 on cell viability, metabolic activity and proliferation was determined using the LIVE/DEAD, MTT, total DNA and LDH assays after 1, 4 and 7 days of culture. None of the SMBG concentrations caused significant cytotoxicity, except the highest doses of 150 and 200 μgml-1 which significantly decreased hMSC metabolic activity after 7 days of culture. Cell proliferation decreased as SMBG concentration increased; however none of the SMBGs tested had a significant effect on DNA quantity compared to the control. Confocal microscopy confirmed cellular uptake and localisation of the SMBGs in the hMSC cytoskeleton. Transmission electron microscopy revealed that the SMBGs localised inside the cell cytoplasm and cell endosomes. To correlate the physiochemical properties (agglomerated versus non-agglomerated) of SMBGs with cellular behaviour, mono-dispersed bioactive glass particles (mono-SMBGs) of 80 mol% SiO2, 20 mol% CaO were synthesised with the diameters of 215 ± 20 nm. The effect of mono-SMBGs on both hMSCs and adipose stem cells (ADSC) were investigated using a range of cytotoxicity assays (LIVE/DEAD, MTT, Alamabar blue and Cyquant). Cytotoxicity data revealed that mono-SMBGs were non-cytotoxic to hMSCs or ADSC. TEM imaging techniques were applied to confirm the internalisation of the particles by the MSCs and ADSCs. It was shown, through confocal imaging, that mono-SMBGs were taken up readily by the cells through a clathrin and caveolae independent endocytosis process. In addition, the differentiation of the stem cells was investigated but the cells maintained their phenotype. Overall, the results presented in this thesis are of great importance for assessing the toxicity of sub-micron bioactive glass particles that may either be used as injectables, generated by wear or degradation of bioactive glass scaffolds or be used for other medical applications such as drug delivery or stem cell tracking.
Supervisor: Jones, Julian ; Porter, Alexandra Sponsor: EPSRC
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral