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.