Foroutan, F; (2015) Sol-Gel Synthesis of Phosphate-Based Glasses for Biomedical Applications. Doctoral thesis , UCL(University College London).

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Abstract

This thesis concerns the development of a new and facile sol-gel synthesis route for production of phosphate-based glasses for biomedical applications including; tissue engineering, imaging contrast agents and drug delivery systems. The structure of the prepared samples was probed by XRD, 31P MAS-NMR, EDX and FTIR spectroscopy that confirmed successful synthesis and production of phosphate based glasses via the sol-gel method. In this study, for the first time, quaternary phosphate-based sol-gel derived glasses in the P2O5–CaO–Na2O–TiO2 system with a high TiO2 content of up to 30 mol% were synthesised. While incorporating a high percentage of titanium into the phosphate network is non-trivial via traditional melt quench methods. Investigation of quaternary glasses with the general formula of (P2O5)55–(CaO)25–(Na2O)(20-x)–(TiO2)x, where X = 0, 5, 10 or 15 revealed, substituting titanium in place of sodium significantly improves the stability and prolongs the degradation of these glasses, which opens up a number of potential biomedical applications. Cell studies on titanium-stabilised glasses suggested glasses containing 5 or 10 mol% TiO2 have optimal potential for bone tissue engineering applications. Electrospraying was used to prepare (P2O5)55–(CaO)30– (Na2O)15 glass nanospheres with a diameter size range of 200-500 nm. These glass nano spheres were used as a transient contrast agent for ultrasound imaging to label mesenchymal stem cells and it was determined in vitro and in vivo that these nanospheres had a detection limit of 5 and 9 μg.mL-1, respectively. Cell counts down to 4000 could be measured with ultrasound imaging with no cytotoxicity at doses required for imaging. Glass nanospheres were also used as a carrier for drug delivery applications with a linear release of tetracycline hydrochloride molecules within the first 4 hours of the study period. Importantly, ion release studies confirmed these glass nanospheres biodegrade into an aqueous medium with degradation products that can be easily metabolised in the body. To the knowledge of the author, this is the first report of sol-gel synthesis and electrospraying to prepare glass nanospheres at low processing temperature and the first use of such a system for both diagnostic and therapeutic purposes.

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