Continuous production of uniform chitosan beads as hemostatic dressings by a facile flow injection method

In this work, we developed a facile flow injection method to fabricate chitosan beads of uniform size in a continuous manner and assessed their properties as hemostatic dressings. Chitosan was dissolved into the ionic liquid 1-ethyl-3-methylimidazolium acetate (EMIM Ac) to form a solution, and then the chitosan/EMIM Ac solution was flow injected into ethanol to form beads of uniform size. The formed chitosan beads were obtained following the exchange of ethanol solvent with water and freeze-drying. The overall process is ecofriendly and scalable without acid/alkali treatment or the use of cross-linking agents. The morphology, swelling, and cytotoxicity of the chitosan beads were characterized. The blood coagulation and whole blood clotting kinetics of the chitosan beads were also studied. The chitosan beads have a significantly high swelling capacity. They can absorb 30 times as much water and 40 times as much PBS/0.9% NaCl solution as their dry mass. Cytotoxicity was not observed on NIH3T3 fibroblast cells after 24 h- or 48 h-incubation, when the concentration of the chitosan beads was 1.2 mg mL^-1 or lower. Pig whole blood quickly lost its flowability in 10 min after the blood (1 mL) was incubated with 1 mg of chitosan beads. The whole blood clotting kinetics results showed that the chitosan beads efficiently caused the pig whole blood to clot with the absorbance of red blood cells (RBCs) dramatically reduced in 20 min and further reduced in 1 hour. The chitosan beads were shown to be biocompatible with excellent hemostatic properties. This work can apply a simple method to prepare chitosan beads for trauma hemostasis and broaden chitosan processing such as continuous manufacturing and 3D printing.