Enzymatic modification and characterization of chitosan-based hydrogels

In the present thesis, a natural biopolymer chitosan was crosslinked with glutaraldehyde and chitosan hydrogels were synthesized.In order to increase the water holding capacity of the hydrogels, they were modified using lipase and penicillin acylase enzymes and also alanine and leucine aminoacids. In the present thesis, the swelling behavior of the all synthesized hydrogels were investegated. FT-IR, TGA, DSC, XRD and SEM analysis were carried to determined the structural, thermal, morphological and surface-sectional properties of the pure and modified hydrogels and changes resulting from structures of enzyme and aminoacid were identified. For all hydrogel samples, swelling experiments were investigated at 25°C and in solutions with different pH values, it was found that, the highest swelling ratio for all the hydrogels was obtained at low pH value. At low pH values, enzyme and aminoacid added chitosan hydrogels have higher swelling degree than pure chitosan hydrogel. The hydrogel samplescontaining 0.6 g of penicillin acylase, 0.04 g of lipase and 0.4 g alanine and leucine have the highest equilibrium swelling ratios.FT-IR specta of all hydrogels was investigated and characteristic peaks of enzyme, aminoacid and glutaraldehyde were obtained. For analysis the thermal properties of all hydrogels, TGA thermograms were investigated and it was found that; modified hydrogels have a significant weight loss at lower temperatures than pure chitosan hydrogel. The morphology of the pure and modified chitosan hydrogels was investigated by X-Ray diffraction. XRD results showed that, characteristic diffraction peaks were obtained for modified hydrogels. Surface morphology of all hydrogels were obtained using scanning electrone microscope and an increase in pore size in the surface of modified hydrogels was observed. According to all results, chitosan hydrogel was modified with enzymes and aminoacids.