Normal-pressure-prepared chitosan carbonate liquid dressing: Spontaneous transformation into a pure chitosan water-resistant film and enhanced wound repair

Liquid dressings are essential in wound care due to their excellent conformability and spontaneous film-forming properties. However, their application is hindered by two key challenges: strict biocompatibility requirements and the need for water-resistant film formation upon drying. Additionally, incorporating active repair functions is extremely difficult. Chitosan, a natural biopolymer with proven wound-healing properties, could address these limitations. However, conventional solubilization methods using acetic acid compromise biocompatibility and impede water-resistant film formation. Herein, we report the first normal-pressure synthesis of purified chitosan carbonate liquid dressing using an ammonium bicarbonate-mediated acetate replacement strategy. This solution spontaneously forms a water-resistant film of pure chitosan upon drying (water contact angle: 99.4°). In full-thickness wound models, it demonstrated remarkable reparative efficacy, including hair follicle regeneration within 10 days, a feature absent in commercial benchmarks like 3 M Cavilon. Importantly, this chitosan carbonate liquid dressing not only overcomes the limitations of conventional chitosan-based solutions in direct biomedical applications but also provides a new repair-facilitating option for the limited pool of liquid dressings. Its unique transformation into a pure chitosan film upon drying resolves long-standing processing limitations of chitosan, unlocking broader applications in biomedical fields such as drug delivery and tissue engineering.