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Title: Tailoring the nanostructure of sol-gel derived bioactive glasses and investigating their interactions with proteins
Author: Lin, Sen
ISNI:       0000 0004 2682 5764
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2010
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Sol-gel derived bioactive glasses with the 70S30C composition (70 mol% SiO2 and 30 mol% CaO) have high potential as materials for bone regeneration and devices for sustained drug delivery. They bond to bone and have a unique tailorable nanoporosity, which affects protein adsorption and cellular response. The first aim of this thesis is to fully characterise the evolution of the nanoporous structure of sol-gel derived bioactive glass for the first time, to fully understand its nanostructure evolution and control. Nanoparticles that were produced early in the sol-gel process, agglomerated into larger particles during gelation and during thermal stabilisation. Calcium was found to not enter the silica network until the material was heated to 400 °C. This has implications for the homogeneity of the calcium distribution in sol-gel derived bioactive glasses. Region separation was found within sol-gel derived bioactive glass monoliths produced by the standard procedure. The calcium concentration and nanoporosity were found to be higher near the edge of the monoliths. This is believed to be caused by calcium accumulation on the outer surface of the monoliths during the drying stage of the sol-gel process. The homogeneity of monoliths was successfully improved by using Teflon moulds. To provide further control of the nanostructure of 70S30C, a method for increasing the nanopore diameter from 12 nm to 30 nm was devised by adding specific amount of trimethylethoxysilane (TMES) during the sol-gel process. A series of amounts of TMES were added at different time points during the sol-gel process. Solid state nuclear magnetic resonance (NMR) and electron microscopy were used to explore the mechanisms behind the changes in nanostructure. Protein adsorption to sol-gel glass was investigated using in situ studies by monitoring the adsorption of fluorescent-labelled proteins onto various types of solgel derived bioactive glasses under confocal microscope with fibrinogen as model protein. Fibrinogen molecules were found to penetrate into inner nanopores of TheraGlass® (a commercial glass with 17 nm nanopores) whereas no penetration was found into sol-gel derived silica (with 3 nm nanopores). Protein interactions were further studied by conducting bioactivity tests with SBF supplemented with 10% serum. Apatite deposition was found inhibited by the interference of serum proteins.
Supervisor: Jones, Julian Sponsor: NovaThera Ltd ; Society of Chemical Engineering ; EPSRC ; Royal Academy of Engineering ; Royal Society ; Philip Leverhulme Prize
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral