Designing cryogels through cryostructuring of β-chitin nanofibers to reinforce polyelectrolyte complexes for non-compressible hemorrhage control

β-Chitin nanofibers enable freeze–thaw reinforcement of hemostatic cryogels. • Freeze–thaw cycling improves structural integrity and rapid blood absorption. • β-Chitin nanofibers mainly enhance coagulation through the intrinsic pathway. • The sponges show low hemolysis and high cytocompatibility in vitro. • An optimized sponge achieves 3.5 s hemostasis in a rat liver injury model. Non-compressible hemorrhage remains a major clinical challenge, requiring hemostatic materials with rapid blood absorption and sufficient mechanical robustness. Conventional carboxymethyl chitosan (CMCS)/sodium alginate (SA) polyelectrolyte complex (PEC) sponges exhibit high swelling capacity but limited uptake kinetics and mechanical strength. Here, β-chitin nanofibers (β-ChNFs) were incorporated into the CMCS/SA system to establish a freeze–thaw reinforcement strategy depended on β-ChNFs. Repeated freeze–thaw cycles had little effect on the storage modulus (G′) of CMCS/SA alone, whereas G′ progressively increased with the number of cycles in β-ChNF-containing systems. After six freeze–thaw cycles and electrostatic complexation, the resulting double-network sponges featured layered, stacked pore walls that conferred excellent shape recovery and fatigue resistance, together with rapid blood absorption and enhanced platelet–red blood cell adhesion, thereby accelerating blood clotting. The β-ChNF-dependent procoagulant enhancement was mainly associated with activation of the intrinsic coagulation pathway, and the sponges also exhibited favorable hemocompatibility and cytocompatibility. In a rat liver perforation model, the optimized sponge demonstrated significantly superior hemostatic performance compared with a commercial gelatin sponge, achieving a hemostasis time of 3.5 s and blood loss of 80 mg, underscoring its strong potential for controlling non-compressible hemorrhage. Download: Download high-res image (144KB) Download: Download full-size image