Abstract: A series of konjac glucomannan (KGM) hydrogels were prepared using chitosan-fulvic acid microparticles (CFMPs) as the reinforcing agents. CFMPs possessed high surface density and oxygen-containing functional groups, which could induce hydrogen-bonding interaction between KGM and CFMPs to form a more dense network structure. The effects of CFMPs on the network structure and releaseing behavior of KGM hydrogels were evaluated. The rheological results revealed that the regular change in the steady shear viscosity and dynamic viscoelasticity of all hydrogel-forming solutions was attributed to the reinforced network structure with strong interaction. Fourier transform infrared spectral analysis indicated that the carboxyl groups (–COOH) in CFMPs successfully formed hydrogen bonds with the hydroxyl groups (–OH) in the KGM polymer chains. Scanning electron microscopic images revealed that the structure of hydrogels was dense with interconnected pores. In addition, the in vitro drug-releasing behavior of KGM/CFMP hydrogels in artificial intestinal and gastric fluids was investigated. KGM/CFMP composite hydrogels possessed excellent pH-responsive property due to the protonated amine groups (–NH3+). Therefore, KGM/CFMP composite hydrogels have a huge potential as a pH-responsive drug delivery system.

Key words: konjac glucomannan; chitosan-fulvic microparticles; hydrogel; pH-controlled release