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A team of researchers in the Biomaterials and Tissue Engineering Division of ¹û¶³Ó°Ôº's Eastman Dental Institute is at the forefront of developing degradable glass for a spectrum of medical applications. The team has recently received almost £1million in collaborative funding from the Engineering & Physical Sciences Research Council (EPSRC) to advance their research.

Led by Professor Jonathan Knowles, the team is interested in phosphate-based glasses and their possible use for a variety of medical applications. "Phosphate-based glass is completely different to the silica-based glass used for window panes or bottles," explained Professor Knowles. "Although they look similar, phosphate-based glass is degradable, and we can alter the rate of degradation from one hour to the material being almost insoluble, depending on requirements."

Up until now, the material has been created by casting it in a furnace that reaches temperatures of over 1000°C, but a technique has recently been developed by Professor Knowles' collaborators at the University of Kent to manufacture the glass by synthesis via the sol-gel route, where glass is formed at lower temperatures of 300-400°C. "Sol-gel and melt-derived glasses are structurally similar," says Professor Knowles. "However, the sol-gel glass process extends the region of glass forming, so we can create certain chemical compositions that were previously impossible. We can also potentially create some unusual structures, such as high levels of porosity."

Fighting infection

The EPSRC has awarded £480,000 to the team, in collaboration with the universities of Kent and Warwick, to develop a new range of phosphate based sol-gels that can fight bacterial infections by releasing antimicrobial ions such as copper and silver. "If, for example, a patient has had a cyst surgically removed, some potentially infectious bacteria could remain in that area. By implanting a sol-gel, the microbial ions will be released as the material degrades, getting rid of the bacteria from the locality without the need for antibiotics," explained Professor Knowles. "Likewise, a strip of sol-gel could be applied to the gum margin to deal with gum infections."

Another strand of the team's research has also received £400,000 from the EPRSC, which will allow the scientists to examine the relationship between the structures and properties of various phosphate-based glasses. The multidisciplinary project - again with colleagues from the universities of Kent and Warwick - will conduct solid-state nuclear magnetic resonance tests, advanced neutron and X-ray scattering experiments and characterisation of the materials' thermal and degradation properties.

Rebuilding bone

These tests should identify possible applications for certain compositions of glass, such as which rate of degradation is suitable for a particular healing process. Professor Knowles explains: "At the institute, we often deal with patients who have experienced bone loss, and filling the defect with sol-gel can allow the bone to grow through. Depending on the porosity of the glass and the individual circumstances, the material can act as a scaffold that dissolves so that by the time the bone has healed, the glass has completely dissolved. This project will allow us to investigate the possibilities of these materials, and also give us a better understanding of how the materials interact."

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