Green Fabrication of Chitin/Chitosan Composite Hydrogels and Their Potential Applications.

Chitin is the second most abundant natural polysaccharide with biocompatibility and bioactivity. Aqueous KOH/urea solution is reported for rapid dissolution of chitin, therefore providing a greener and more efficient avenue to fabricate chitin-based functional materials. Chitosan is the most important derivative of chitin with the acetylation degree lower than 60%. Herein, novel chitin/chitosan composite hydrogels are fabricated from the green and highly efficient KOH/urea aqueous system for the first time. Both chitin and chitosan are dissolved in aqueous KOH/urea solutions, then cross-linked by epichlorohydrin to form bulk chitin/chitosan composite hydrogels (CCGEL). The structural, thermal, mechanical, and swelling properties of CCGEL are thoroughly studied. The cell studies show that NIH-3T3 cells self-assemble to form regular 3D multicellular spheroids on the CCGEL samples with high viability. L929 cells proliferate and intend to form cell aggregates, and the size of the cell aggregates becomes greater with the increase of chitosan loading. Additionally, the CCGEL samples exhibit antibacterial activities. Thus, this pioneering work has provided crucial information for novel chitin/chitosan composite materials constructed via the direct dissolution of chitin and chitosan in aqueous KOH/urea solutions, and presented their potential applications in the cell culture and antibacterial fields.