Preparation of chitosan-Cu2+/NH3 physical hydrogel and its properties.

Chitosan (CTS) physical hydrogels crosslinked under gaseous ammonia atmospheres have attracted considerable attentions for their abilities to maximize the biological activities of CTS while maintaining their biocompatibility. However, poor mechanical properties significantly limit their application. The CTS-metal ion complexing hydrogels showed better mechanical properties. However, the formation process is uncontrollable, and the high dosages of metal ions used may cause cytotoxicity. In the present work, CTS-Cu2+/NH3 physical hydrogel with excellent comprehensive properties was prepared by ammonia fumigation and metal ion complexation. Its formation mechanism and structure were investigated. The above physical hydrogel revealed excellent mechanical properties with the mechanical strength up to 0.30 MPa, significantly higher than CTS/NH3 hydrogel, even at much lower Cu2+ contents. And CTS-Cu2+/NH3 hydrogel is more thermal stable than CTS/NH3 hydrogel. In addition, it exhibited specific killing effects on Pseudomonas aeruginosa. These results suggest that CTS-Cu2+/NH3 physical hydrogel has a great application potential as a wound dressing.