Injectable biochar-reinforced alginate hydrogels for hemostasis under wet and deformable conditions

Uncontrolled bleeding under wet and deformable conditions remains a major challenge for conventional hemostatic materials, which often suffer from limited tissue adhesion and poor mechanical adaptability. Here, we developed an injectable sodium alginate hydrogel ionically cross-linked with Ca²⁺ and reinforced with hazelnut branch-derived biochar (HB) to improve structural stability and local hemostatic performance. The HB-containing hydrogel exhibited pronounced shear-thinning behavior, high injectability, enhanced wet tissue adhesion, and self-healing efficiency exceeding 80%, while achieving an adhesive strength of approximately 420 kPa. Physicochemical characterization indicated homogeneous HB incorporation and Ca²⁺ retention by HB, which may influence the local ionic environment of the hydrogel network. In vitro studies demonstrated good cytocompatibility and hemocompatibility. In hemostatic assays, 6A7C-HB exhibited a blood clotting index (BCI) of 4.45%, markedly lower than that of the commercial oxidized cellulose hemostat Surgicel® (26.98%), and shortened the clotting time to 4.4 min compared with 7.5 min for the untreated blood control and 7.2 min for Surgicel®. In vivo evaluation in rat tail transection and liver injury models showed effective hemorrhage control, reducing blood loss by approximately 45-55% compared with untreated controls, while subcutaneous implantation demonstrated acceptable biocompatibility without evidence of significant systemic toxicity or adverse histopathological responses. These findings demonstrate that HB reinforcement provides a simple and effective strategy for developing injectable alginate hydrogels with improved mechanical adaptability and localized hemostatic performance under wet and deformable conditions.