Antibacterial microspheres with a bionic red-blood-cell like hollow structure and superior swelling recovery capacity for efficient traumatic hemostasis

• A bionic red blood cell like microspheres with controllable surface morphology. • The microspheres are microporous structure on the surface and hollow structure inside. • The microspheres formed physical barrier in wound by facilitate aggregations of blood. • The microspheres exhibit hemostasis, antibacterial and histocompatibility performance. Broad interest in developing new commercial hemostatic agents has been widely aroused for massive blood loss in terms of hospital surgery and on the battlefield. In this study, we report biomimetic red-blood-cell like (RBC-like) hydrogel microspheres with controllable surface morphology by adjusting the proportion of carboxylated chitosan (CM) and gelatin (G) using Fe 3+ as crosslinking agent. It is worth noting that the microspheres are similar to RBCs in the dry state, with a microporous structure on the surface and a hollow structure inside, and enable restoration to the microsphere shape after absorbing water. The CMG1 microspheres show the best hemostatic effect, as indicated by whole blood coagulation in vitro and rat liver and leg artery damage models in vivo . The microspheres exhibit antibacterial properties against Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ). In addition, the microspheres have satisfactory degradation performance, hemocompatibility, biocompatibility and histocompatibility. This study indicates that these RBC-like microsphere-based hemostatic powders facilitate a physical barrier in wounds by forming aggregations. In addition, the micropores on the surface of the microspheres make it swell rapidly by absorbing blood, aggregating coagulation factors, activating platelets and ultimately accelerating the coagulation cascade to facilitate hemostasis. In conclusion, CMG1 hydrogel microspheres present potential application in the field of emergency hemostasis.