Stopping Blood Loss in Seconds: A Powder That Saves Lives

Millions of lives are lost during accidents and wars – not because injuries are fatal, but because bleeding is uncontrolled. Before patients reach a hospital, the available treatments are just bandages and cotton gauze. These rely on manual pressure, exhibiting poor hemostasis, or the mechanism that leads to cessation of bleeding from a blood vessel. They frequently stick to the blood clot and its removal can disrupt new tissues, trigger re-bleeding, and leave fibrous residues that promote bacterial infection. Moreover, the common patch-type treatments have weak adhesion to wet, irregular, or non-compressible wounds. 

Targeting this, a research team at KAIST introduced a powder-type hemostatic agent, called AGCL.

AGCL powder was developed through the chemical crosslinking of sodium alginate (A), gellan gum (G), and chitosan (C) using a glutaraldehyde crosslinker (L), forming a cohesive 3D polymer matrix. Unlike conventional treatments, the powder-based material allows for efficient application to wounds of variable geometry and depth, including deep and irregular sites. 

But that’s not all. AGCL’s groundbreaking effectiveness relies on two mechanisms: hydrogels and gelation.

Hydrogels are crosslinked polymer chains with 3D network structures, which can absorb very large amounts of fluid. Because of its soft structure, porosity, and fluid retention capacity, they closely resemble living tissues. AGCL replicates a hydrogel structure, which allows for its superior absorption. 

Upon contact with blood, the powder undergoes rapid ionic gelation, primarily driven by the interaction between gellan gum and sodium alginate with calcium ions abundant in the blood. Sodium alginate and gellan gum are both polymer chains with negatively charged COO^- groups in their repeating blocks, which makes them repel, staying separated. Calcium ions (Ca²⁺) in the blood can instantly bind to two carboxylate groups, creating ionic crosslinks that connect the polymers into a three-dimensional hydrogel network within seconds. At the same time, the crosslinked AGCL matrix facilitates erythrocyte (red blood cell) and platelet (cells that help with blood clogging in your body) aggregation, forming a dense clot that entraps blood components and accelerates thrombus (blood clot) formation. 

This innovative mechanism of AGCL offers powerful benefits. 

First, tissue adhesion. This is when a band of scar tissue joins two surfaces of the body that are usually separate. Sufficient adhesive strength enables the formation of a physical barrier to suppress blood loss and prevent re-bleeding caused by hemodynamic pressure, making it more effective than current bandages that depend on manual pressure alone. AGCL performs enhanced adhesion due to the rapid formation of a hydrogel layer that sticks to the surface of the skin. Hydrogen bonding between hydrogel and blood or tissue proteins, as well as electrostatic interactions between the positively charged chitosan in the powder and negatively charged blood cells creates a strong gel layer that seals the wound.

Second, biocompatibility. This is the ability of a substance to interact with the body's biological systems without causing negative effects such as inflammation, toxicity, or immune reaction. The low hemolysis (the destruction of red blood cells) of AGCL is attributed to the intrinsic biocompatibility of its carbohydrate-based components: alginate, gellan gum, and chitosan. These sugar-based polymers are similar to molecules already found in the body, preventing them from triggering an immune response.

Finally, antibacterial performance. AGCL-treated agar plates showed complete inhibition of bacterial growth. This is because chitosan is known to possess intrinsic antibacterial properties, which may arise from protonated amino groups that disrupt bacterial membranes through electrostatic interactions or local ionic imbalance. Additionally, the crosslinked hydrogel forms a porous mesh that physically traps bacteria and keeps antibacterial agents concentrated together at the wound site, enhancing antibacterial effectiveness through prolonged local contact.

The future potential for AGCL seems infinite. Suited for emergency care, surgical applications, and deployment in resource-limited settings, AGCL is a promising candidate for next-generation hemostats in trauma care, surgery, and emergency medicine. Park Gyu-soon, a KAIST doctoral student serving in the Korean military who participated in the research, stated, “I began this research with the thought of saving even one more soldier.”

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