Neel, E.A.E-S.A.; (2006) Collagen-phosphate glass fibres for biomedical and tissue engineering applications. Doctoral thesis , University of London.

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Abstract

The aim of this project was to develop three-dimensional (3-D) constructs of phosphate-based glass fibres (PGF) incorporated dense collagen matrices for biomedical and tissue engineering applications. For this, a novel method of "plastic compression" (PC) was used which rapidly removes fluid from hyper-hydrated collagen gels through the application of unconfined compressive load. The project objectives were: the understanding of structure-property relationship of PGF the understanding of the mechanisms of PC to produce dense collagenous matrices, and the application of PC to produce cellular 3-D constructs of PGF reinforced collagen matrices. PGF are unique glasses as they are degradable and biocompatible, and their degradation can be controlled through their chemistry. Two different quaternary glass systems incorporating CuO and Fe2O3 into the ternary glass system (in molar percentage) 50 P2O5- 30 CaO-20 Na2O were developed for either antibacterial or tissue engineering applications. These additional oxides were incorporated into the glass structure by partially substituting Na20. The rate of degradation was significantly decreased by the incorporation of both oxides possibly due to increased cross-link density, which correlated with an increase in the density and glass transition temperature. There was a further decrease in degradation with increasing fibre diameter. The amount of Cu2+ release increased with increasing CuO content, and 10 mol % was the most effective in killing Staphylococcus epidermidis. YqjOt, had a much more significant effect on rate of degradation, and the rate of Fe3+ release decreased with increasing Fe203 content. From the compositions and fibre diameters investigated, fibres containing 3-5 mol % Fe203 with a diameter of 30 urn were more durable, and therefore suitable for use as scaffolds. Furthermore, upon long term degradation, the iron containing glass systems showed the potential for tube formation. PC depends mainly on the ability of collagen to undergo creep deformation and no recovery upon load removal. Using this principle, a dense collagen matrix with improved mechanical properties was produced. PC was also successful in producing PGF-PC collagen constructs with different compositions. It was anticipated that PGF would initially further enhance the mechanical properties of the constructs. Moreover, PGF also provided the intriguing possibility of capillary-like channels within the collagen for cell and nutrient transportations. The effect of PGF incorporation was assessed morphologically, mechanically, and biologically using live/dead staining. Increasing the proportion of PGF yielded significantly stiffer, stronger constructs while compromising their compliance. At greatest, only 20 % cell death due to either PC or PGF incorporation occurred, however, a significant increase in cell viability after 24 hours was observed. The findings suggested that PC is effective for engineering composite, biomimetic collagen matrices with controllable properties.

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