Rapid, organic-solvent-free freeze-thaw fabrication of pure chitosan sponges for scalable potential wound dressing applications

Chitosan sponges hold significant promise for advanced wound dressings; however, their widespread adoption is hindered by complex and costly fabrication processes that depend on organic solvents, lyophilization, and alkaline immersion. Here, we introduce a novel organic-solvent-free freeze-thaw strategy to overcome these challenges. The integration of ammonium bicarbonate into acetic acid-dissolved chitosan, followed by a single freeze-thaw cycle (freezing at -20°C and thawing at 26°C within 1 hour), results in the spontaneous formation of pure chitosan sponges. The resulting material exhibits exceptional tensile strength (26.35 kPa at 1.57% solid content) without the use of potentially harmful crosslinkers. This approach eliminates the need for energy-intensive lyophilization and organic solvents, thereby reducing production time and cost by over 90% compared to traditional methods. In vivo studies using SD rat models demonstrate 67% faster epithelialization compared to gauze controls, along with full biocompatibility attributed to the inherent biological properties of pure chitosan. With minimal equipment requirements, environmental sustainability, and high scalability, this method establishes a new benchmark for biomaterial manufacturing. Its potential for clinical translation in emergency wound care and tissue engineering applications is underscored, pending further validation.