Study Of The Synthesis And Properties Of Chitosan Oligosaccharide-graft-acrylic Acid Biodegradable Crosslinker And Hydrogel

In this study, a new water soluble and biodegradable crosslinker of chitosan oligosaccharide-graft-acrylic acid (CSO-g-AA) was synthesized, which was used to prepare novel biodegradable macroporous hydrogels, and the degradation was studied.The chitosan crosslinker was synthesized through the amidating reaction of amino groups in the chitosan oligosaccharide (CSO) chains and carboxyl groups in acrylic acid (AA) under the catalysis of1-ethyl-3-(3-dimethylaminopropyl)-carbodiimidehydro-chloride (EDC) and N-hydroxysuccinimide (NHS). The amidating reaction is able to provide polymerizable carbon-carbon double bonds for CSO. The chemical structure of the resluted compound chitosan oligosaccharide-graft-acrylic acid (CSO-g-AA) was characterized by Fourier transform infrared spectroscopy (FTIR) and1H nuclear magnetic resonance (1H NMR) spectroscopy. The content of double bonds was measured by titration analysis. The measurement showed that the grafting ratio of AA on CSO was about3.5%(averagely two acryoyl groups per CSO-g-AA chains) when the applied molar ratio of AA to CSO was1.0. Polyacrylamide (PAM) hydrogels were prepared by copolymerization of acrylamide and CSO-g-AA, which can be degraded to water soluble polyacrylamide chains under the catalysis of snailase.Polyacrylamide (PAM) cryogels were synthesized by the free radical polymerization of acrylamide and CSO-g-AA using a modified freezing polymerization method. A cation surfactant dodecyldimethylbenzylammonium bromide (DDBAB) was used during the cryo-polymerization process. The function of DDBAB is that it will react with the water soluble initiator ammonium persulfate (APS) to form a hydrophobic initiator dodecyldimethyl-benzylammonium persulfate (DDBAPS) and the cryo-polymerization reaction is initiated by DDBAPS aggregates with the size of hundreds of nanometers. The obtained cryogels are able to be degraded into linear chains as a result of the degradation of the crosslinking point in appropriate enzyme solutions.The cryogels were treated with snailase which was chosen as a model enzyme to perform the biodegradation process. The degradation was monitored by morphological studies using confocal laser scanning microscope (CLSM) and scanning electron microscope (SEM), dynamic mechanical measurements of the storage modulus, and the swelling measurements. The duration of degradation process was adjustable from one month to two months when using different concentration of snailase solutions.