Chitosan (CS) is the deacetylated derivative of the biopolymer chitin. The attractiveness of chitosan for biomedical applications is attributed to the fact that it is biodegradable, biocompatible, non-immunogenic, non-carcinogenic and, most importantly, to the fact that it is a cationic polysaccharide. Chitosan-based hydrogels have been the focus of much of this previous work. Novel chitosan based hydrogels are continuously being produced, each new gel presenting different morphologies and physical characteristics that in turn have an effect on the biomedical application they are designed for. The scope of this thesis was to further the knowledge on chitosan based hydrogel systems, designed for biomedical applications, a number of previously unreported systems are described including a novel physically crosslinked chitosan hydrogel achieved by ionic crosslinking with adenosine tri-phosphate (A TP). This produced an array of different beads and their morphological, physical and protein drug delivery properties were extensively assessed. The results showed that - these gels behaved profoundly different to similarly ionically crosslinked systems. Utilizing a novel technique, 'microbubbling', to induce porosity into otherwise low porosity hydrogels a series of gels have been successfully produced from- a high viscosity chitosan solution. Normally this technique is only applicable to low viscosity liquids but we have shown that micro bubbles were indeed introduced into the chitosan hydrogels. The morphology of these gels has been carefully analysed. Gelation of chitosan solutions has also been achieved by utilizing a novel electrochemical process. Inducing gelation of chitosan solutions was achieved in a simple electrochemical cell. The effect of various counterions was also studied. The results show that gels were produced with profoundly different morphologies. The electrochemically induced gels showed a variety of different and controllable porosities. Such gels are believed to be potential candidates for such biomedical applications such as drug delivery and tissue engineering. Chitosan also has the capability of forming 'thermosetting' gels. This thesis reports for the first time on the use of such a system as 'fiducial markers' for computer assisted surgery. Fiducial markers are usually titanium screws which are surgically implanted on the bone in the area proximal to the operations and used as 'reference points' by the navigational system of the computer. In our study the titanium screws were replaced by a mix of thermo gelling hydrogel and radio-opaque solutions which were injected in the desired location, without the need for surgical implantation, and then analyzed. Promising results were obtained via computer aided topography.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:506749 |
| Date | January 2008 |
| Creators | Achilli, Luca G. C. |
| Publisher | Queen Mary, University of London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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