Chitosan Hydrogels and their Glutaraldehyde-Crosslinked Counterparts as Potential Drug Release and Tissue Engineering Systems - Synthesis, Characterization, Swelling Kinetics and Mechanism

Snail shells had been utilized to prepare chitosan and hydrogels of the chitosan were also prepared and crosslinked with varying amounts of glutaraldehyde to achieve different crosslink densities between 0.75 and 1.50. The materials were characterized in terms of the dependence of their swellabilities on time and pH. FTIR analysis was also carried out on the hydrogels and the results obtained show a band at 3451 cm-1, attributed to O-H stretching of the chitosan. The crosslinked hydrogels also showed an N-H bending vibration at 1635 cm-1 which has a reduced intensity and has moved to a lower wavenumber when compared to the N-H bending vibration of the uncrosslinked chitosan hydrogels at 1652 cm-1. The swelling studies showed that the extent of swelling of the hydrogels was dependent on the crosslink density (CD), increasing as CD increased. Uncrosslinked chitosan hydrogel had maximum swelling of 162.71% while that for the crosslinked chitosan hydrogels with CD of 0.75, 1.00 and 1.50 were 119.87%, 93.21% and 87.65% respectively. In all cases, their crosslinked counterparts had decreased swellabilities suggesting that, the crosslinked chitosan hydrogels can be used for a more controlled delivery of drugs and as efficient materials for tissue engineering. The chitosan hydrogels showed maximum percent swellability in highly acidic medium (pH2) equally suggesting the potential of these hydrogels as drug release systems in this medium. The swelling of the chitosan hydrogels followed second-order kinetics and their swelling diffusion exponents ranged from 0.142 to 0.155, indicative of a Less Fickian diffusion or transport mode.