Selectively oxidized chitin as a degradable and biocompatible hemostat for uncontrolled bleeding and wound healing

Chitin (CT), one of the most abundant biopolymers, is insoluble in both dilute aqueous solutions and common organic solvents. In traditional hemostatic applications, chitin must be either converted into acid-soluble chitosan by removing acetyl groups or dissolved in an alkaline aqueous solution at -20 °C. However, acetyl groups are more advantageous than amino groups in promoting hemostasis, biocompatibility, biodegradability, and wound healing. A significant challenge remains in retaining acetyl groups while directly preparing a hemostatic agent from chitin without requiring its dissociation. In this study, we have successfully applied oxidized chitin (OCT) as a hemostatic material, which is directly derived from chitin through a TEMPO-mediated selective oxidation of C6 primary hydroxyl groups to carboxyl groups. Due to its significantly higher hydrophilicity compared to chitin, OCT rapidly forms a gel upon contact with blood, efficiently sealing broken blood vessels and facilitating wound healing. Among OCTs with varying carboxylate contents and the commercial chitosan hemostat Celox™, OCT-24 demonstrated not only the best hemostatic performance in some injury models but also excellent biocompatibility and biodegradability, effectively preventing tissue adhesion and promoting wound healing. The selective oxidation offers a straightforward method for developing a highly effective hemostatic material from chitin to address uncontrolled massive bleeding.