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.