Preparation and characterization of chitosan physical hydrogels with enhanced mechanical and antibacterial properties.

The chitosan physical hydrogels formed under gaseous ammonia atmospheres usually have poor mechanical properties and low antibacterial activities, which limit its application as biomaterials. In the current study, CTS-Ag+/NH3 physical hydrogels with great comprehensive properties were prepared by the gelation of chitosan in the presence of AgNO3 under a gaseous ammonia atmosphere. Compared with the previously reported hydrogels made with chitosan and AgNO3, the CTS-Ag+/NH3 hydrogels were more homogeneous and transparent. In addition, the AgNO3 content in the hydrogels was decreased to 0.064-0.424wt.%. The formation mechanism and the influence of reaction conditions on the structures and properties of CTS-Ag+/NH3 physical hydrogels were characterized by FT-IR, SEM, XPS, XRD and rheological measurement. Tensile testing suggested that CTS-Ag+/NH3 physical hydrogels had a higher tensile strength than the CTS/NH3 hydrogel. Moreover, the CTS-Ag+/NH3 physical hydrogels showed excellent antibacterial activities against both gram positive and negative bacteria.