Rheological, water uptake and controlled release properties of a novel self-gelling aldehyde functionalized chitosan

In this work, aldehyde-functionalized chitosan was used to prepare gels through Schiff base formation between the aldehyde and the free amine groups. The gels, which were formed in situ without an external crosslinker, were characterized in respect to their rheological properties and water uptake capacity. In addition, the potential use of these gels as drug carriers was investigated using metronidazole (Mw 171 Da), FTIC-dextran (Mw 40 kDa) and bovine serum albumin (Mw 66 kDa), as the model drugs. Higher concentrations of the aldehyde-functionalized chitosan originated more rigid gels, as evidenced by the higher values of complex modulus (G*). The highly porous structure of these gels allowed for more than 400% of water uptake. The release of the model drugs followed a near zero-order release profile. The molecular size as well as the pH of the medium influenced the amount of drug released, where the higher the pH, the slower the resulting drug release.