Currently, massive wound bleeding remains a leading cause of hemorrhagic shock and prehospital trauma deaths worldwide. Approximately 40 % of trauma-related deaths are due to uncontrolled bleeding [1], [2]. The hemostatic function is an essential component of medical wound dressings. Wound dressings play a crucial role in trauma management and surgical procedures [3], [4]. When the human body experiences an injury, one of the most critical procedures is to stop bleeding promptly to prevent excessive blood loss. Hemostatic dressings aid in accelerating the process of hemostasis, reducing blood loss, and are vital for successful trauma treatment [5], [6]. Additionally, hemostatic dressings provide a physical barrier to block bacteria and other harmful microorganisms from entering the wound, thus reducing the risk of infection and promoting the wound-healing process [7], [8]. In specific situations, such as surgical procedures or emergency cases with significant trauma, hemostatic dressings can also provide additional pressure to help control bleeding [9], [10].

Traditional hemostatic materials such as gauze, tourniquets, sponges, and bandages have been limited in their effectiveness in treating uncontrollable bleeding [11]. Because the need to mitigate uncontrolled bleeding in emergency, surgical, and battlefield environments has yet to be fully met, developing an ideal hemostatic composite remains a challenge. The hemostatic powder has the advantages of comprehensive coverage, short hemostasis time, good hemostatic effect, and easy operation under endoscopy [12], [13]. In addition, the hemostatic powder can be sprayed on irregularly--shaped and incompressible wound surfaces to facilitate close contact with the wound [14], [15], [16]. However, hemostatic powder may have poor tissue adhesion properties. Benefiting from the biocompatibility, adhesiveness, and natural extracellular matrix-mimicking ability, hydrogels, particularly those based on natural polysaccharides, have received increasing research in recent years [17], [18], [19].

Chitosan-based hemostatic hydrogel is a novel medical dressing, which can quickly form a clot on the surface of a wound, stopping bleeding, preventing wound infection, and promoting wound healing [20], [21]. For example, in a prior study, konjac glucomannan as the functional moieties and chitosan as the backbone were applied to form an injectable hydrogel by the Schiff base reaction of dodecyl-modified N-carboxyethyl chitosan and oxidized konjac glucomannan. This hydrogel possessed tissue adhesive, self-healing, and antibacterial capabilities, which was used to stop the wound bleeding and tissue adhesion after surgery [22]. However, attributed to the poor solubility, it has remained a significant challenge to design the pristine chitosan-based hydrogel. With controllable solubility and machinability, the derivatives of chitosan, as alternatives, are being frequently investigated in formulations of hydrogels [23], [24]. Among the derivatives, quaternized chitosan (QCS)-based hydrogel not only serves as a hemostatic material and physical barrier to control bleeding and prevent infection but also creates a favorable moist environment for wound healing, making it a promising wound dressing [25], [26]. Besides, the antibacterial activity of quaternized chitosan is stronger than chitosan [27]. Polydopamine possesses abundant catechol groups, which allow it to adhere to various surfaces [28].

Herein, an adhesive hydrogel system composed of QCS-Methacryloyl (QCS-MA), polyvinylpyrrolidone (PVP), and dopamine (QMPD hydrogel) was designed, and it was found that this hydrogel had excellent hemostatic properties. The hydrogen bonds between the tissue surface and PVP, the hydrogen bonds between the tissue surface and dopamine (DA), and the adhesive properties of DA contributed to its outstanding adhesion to wet tissue surfaces and hemostatic abilities (Scheme 1). The QMPD hydrogel's superior hemostatic capability is validated in vivo by establishing Sprague-Dawley (SD) rat tail amputation and liver bleeding models. Even in the moist and dynamic environment of tail amputation or liver bleeding, the QMPD hydrogel is able to seal the bleeding wounds quickly. Our research findings demonstrate the immense potential of the QMPD hydrogel in emergency hemostasis and promoting wound healing, making it a promising candidate for emergency hemostasis applications.