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Thermosensitive chitosan hydrogel for biomaterial applications. Rong Zeng Queen Mary, University of London Fudan University Supervisor : Dr. Ray Smith Xin Chen. Contents. Background Chitosan Thermosensitive hydrogel Experiments & Some results
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Thermosensitive chitosan hydrogel for biomaterial applications Rong Zeng Queen Mary, University of London Fudan University Supervisor : Dr. Ray Smith Xin Chen
Contents • Background • Chitosan • Thermosensitive hydrogel • Experiments & Some results • GP/chitosan • thermosensitive chitosan hydrogel • Future work
Chitosan • Structure Biocompatibility Biodegradable Bioadhesive
Chitosan Hydrogel Temporary network Safe & reversible Weak mechanical properties Permanent network Stable &good mechanical properties Toxic
Temperature induced gelation Body temperature Injectable Topical drug delivery Tissue engineering Thermosensitive hydrogel
GP&chitosan Chenite et al.(2000) developed a novel approach to produce thermally sensitive neutral solutions based on chitosan /β-glycerophosphate (GP) combinations.
Three types of interactions may be involved in the gelation process: • (1) electrostatic attraction between the ammonium groups of chitosan and the phosphate group of GP; • (2) hydrogen bonding between polymer chains as a consequence of reduced electrostatic repulsion after neutralization of the chitosan solution with GP; • (3) chitosan–chitosan hydrophobic interactions.
NMR test result • 1H-NMR • 13C-NMR • 31P-NMR
1H-NMR 3,4,6 5,6
The line shifting is an indication of an exchange process which is speed up by increasing the temperature.
13C-NMR 1,4,5,3,6,2
Results • 1H NMR data on GP/Chitosan mixture indicates that hydrogen bonds have been disrupted as a result of increasing temperature. If GP alone is heated, the observed shifts are much smaller. • 13C NMR data was difficult to obtain for chitosan solutions, still trying to investigate the affect of temperature . But we expect no major shift. • 31P data again indicate that in mixture of GP/ Chitosan the hydrogen bonds have been disrupted. This is shown in a difference in shift value between GP and GP/Chitosan . We are closely examining the 31P-1H coupled data to verify this.
Thermosensitive chitosan hydrogel PKa Method: 1, alkaline chitosan solution 2, change the PH value of the solution by using different kind of acid solution
alkaline chitosan solution (PH=9.6) pluronic solution (PH=4.4) . Mixed solution (PH=7.0)