PolySTAT-modified chitosan gauzes for improved hemostasis in external hemorrhage

Abstract

Positively-charged chitosan gauzes stop bleeding from wounds by electrostatically interacting with negatively-charged cell membranes of erythrocytes to cause erythrocyte agglutination and by sealing wounds through tissue adhesion. In the following work, nonwoven chitosan gauze was impregnated with PolySTAT, a synthetic polymer that enhances coagulation by cross-linking fibrin, to generate PolySTAT/chitosan gauzes with improved hemostatic efficacy. When comparing nonwoven chitosan and PolySTAT/chitosan to a commercially-available chitosan-containing gauze (Celox® Rapid), no appreciable differences were observed in fiber size, morphology, and pore size. However, PolySTAT/chitosan demonstrated more rapid blood absorption compared to Celox® Rapid. In a rat model of femoral artery injury, PolySTAT/chitosan gauzes reduced blood loss and improved survival rate compared to non-hemostatic controls and Celox® Rapid. While Celox® Rapid had stronger adherence to tissues compared to PolySTAT/chitosan gauzes, blood loss was greater due to hematoma formation under the Celox® dressing. Animals treated with PolySTAT/chitosan gauzes required less saline infusion to restore and maintain blood pressure above the target blood pressure (60mmHg) while other treatment groups required more saline due to continued bleeding from the wound. These results suggest that PolySTAT/chitosan gauzes are able to improve blood clotting and withstand increasing arterial pressure with the addition of a fibrin cross-linking hemostatic mechanism.

Statement of significance: Blood loss remains one of the leading causes of death after traumatic injury in civilian populations and on the battlefield. Advanced biomaterials that interact with blood components and/or accelerate the clotting process to form a hemostatic plug are necessary to staunch bleeding after injury. Chitosan-based gauzes, which stop bleeding by causing red blood cell aggregation, are currently used on the battlefield and have shown variable performance under high pressure arterial blood flow in animal studies, suggesting that red blood cell aggregates require further mechanical stabilization for more reliable performance. In this work, we investigate the binding and cross-linking of fibrin, a major component in blood clots, on chitosan gauze fiber surfaces to structurally reinforce red blood cell aggregates.

Keywords: Chitosan gauze; Fibrin; Hemostasis; PolySTAT; Polymer; Trauma.

Figure 1

Hemostatic mechanisms of PolySTAT/chitosan gauze components. PolySTAT structure reproduced with permission from [16].

Figure 2

Nonwoven gauze manufacturing process.

Figure 3

Fluid absorption behavior of gauze samples. (A) Water contact angle and blood absorption time. (B) Liquid absorption ratio (LAR) and liquid retention ratio under pressure (LRRP) normalized to gauze mass (top) and area (bottom).

Figure 4

In vitro clotting assay results. Hemoglobin absorbance from unclotted blood was measured after incubation of recalcified blood with gauze samples containing 0–1 mg/cm² PolySTAT loading.

Figure 5

Hemostatic efficacy of PolySTAT/chitosan gauzess in rat femoral artery injury models. (A) Workflow schematic and timeline. Modified with permission from [16]. (B) Survival curve for animals treated with PET gauze, Celox® Rapid, chitosan gauze, and PolySTAT/chitosan gauzes. (C) Cumulative hemorrhage volume normalized to survival time. (D) Total infused saline volume normalized to survival time. (E) Mean arterial pressure in the first 0–30 min of saline infusion. (F) Blood lactate concentration in the first 0–30 min of saline infusion. (G) Image of hematoma forming underneath Celox® Rapid gauze.