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Queen Mary University of LondonQueen Mary University of London
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School of Engineering and Materials Science
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PhD Thesis: Physically Crosslinked Chitosan Based Hydrogels for Biomedical Applications

Author: ACHILLI, Luca

Year: 2008

Supervisor(s): Ray Smith

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 (ATP). This produced an array of different beads. These gels behaved profoundly differently 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. The morphology of these gels has been carefully analysed. Gelation of chitosan solutions has also been achieved by utilizing a novel electro-chemical 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 makers 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 thermogelling 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.