BACKGROUND OF THE INVENTION

Disclosed herein are single layered nonwoven wound dressings containing (1) about 5% by weight to about 95% by weight (e.g., 5% to 95%) non-scoured, non-bleached greige cotton fibers (preferably about 30% by weight to about 80% by weight (30-80), more preferably about 50% by weight to about 60% by weight (50-60)), (2) about 5% by weight to about 95% by weight (e.g., 5% to 95%) bleached cotton fibers (preferably about 20% by weight to about 70% by weight (20-70), more preferably about 20% by weight to about 30% by weight (20-30)), and (3) about 5% by weight to about 60% by weight (e.g., 5% to 60%) hydrophobic fibers (e.g., polypropylene, nylon) (preferably about 5% by weight to about 50% by weight (5-50), more preferably about 5% by weight to about 20% by weight (5-20)); all percentages adding up to 100 wt %. Also, multi-layered nonwoven wound dressings, containing (1) at least one inner layer containing (a) about 50% by weight to about 95% by weight (e.g., 50% to 95) non-scoured, non-bleached greige cotton fibers (preferably about 60% by weight to about 80% by weight (60-80); more preferably about 50% by weight to about 60% by weight (50-60)) and (b) about 5% by weight to about 50% by weight (e.g., 5% to 50%) hydrophobic fibers (preferably about 20% by weight to about 40% by weight (20-40), more preferably about 40% by weight to about 50% by weight (40-50)), all percentages adding up to 100 wt %, and (2) at least one outer layer containing (a) about 5% by weight to about 95% by weight (e.g., 5% to 95%) non-scoured, non-bleached greige cotton fibers (preferably about 30% by weight to about 80% by weight (30-80), more preferably about 50% by weight to about 60% by weight (50-60)), (b) about 5% by weight to about 95% by weight (e.g., 5% to 95%) bleached cotton fibers (preferably about 20% by weight to about 70% by weight (20-70), more preferably about 20% by weight to about 30% by weight (20-30)), and (c) about 5% by weight to about 60% by weight (e.g., 5% to 60%) hydrophobic fibers (e.g., polypropylene, nylon) (preferably about 5% by weight to about 50% by weight (5-50), more preferably about 5% by weight to about 20% by weight (5-20)); all percentages adding up to 100 wt %.

Half of all deaths on the battlefield are caused by uncontrolled hemorrhage (Bellamy, R. F., Military Medicine, 149: 55-62 (1984); Sauia, A., et al., Arch Surg., 129: 39-45 (1994)). In addition, high blood loss can lead to hypothermia, multiple organ failure, and infection (Cosgriff, N., et al., J. Trauma., 42: 857-862 (1997); Champion, H. R., et al., J. Trauma, 54: S13-S19 (2003)). Thus, rapid hemostasis is essential for survival and recovery. The development of improved hemostatic agents for use in lethal extremity arterial hemorrhages has increased over recent years. The U.S. Army Institute for Surgical Research (USISR) and the Uniformed Services University of the Health Sciences has outlined ideal properties needed in a battlefield dressing (Abou-Okeil, A., et al., Carbohydr. Polym., 90: 658-666 (2012)). These include the following properties: (1) being able to rapidly stop large vessel arterial and venous bleeding two minutes after application when applied to an actively bleeding wound through a pool of blood; (2) no requirement for mixing or preapplication preparation; (3) simplicity of application by wounded victim, buddy, or medic; (4) light weight and durable; (5) long shelf life in extreme environments; (6) safe to use with no risk of injury to tissues or transmission of disease; and (7) inexpensive (Pusateri, A. E., et al., J. Trauma, 60: 674-682 (2006)). With this list of ideal properties the question arises: Is there any deployed product capable of stopping or reducing groin arterial bleeding and preventing exsanguination that otherwise could not be controlled by the standard gauze dressing? The dressings evaluated by USAISR were the Army Field Dressing (a cotton product of long-standing use), Quikclot®, HemCon®, and Fibrin Sealant. Surface area coverage, sealant efficacy, adherence, and adsorption capacity are all important factors in this challenging area of hemostasis since the geometry and anatomical location of the wounds can vary greatly and factors into the success of patient survival. The Army Field Dressing, which is the standard field dressing used by the military, consists of two layers of gauze that wrap densely packed cotton. It absorbs a large volume of blood and the cotton strands stimulate platelet aggregation. The prohibitive price of Fibrin Sealant which consists of fibrinogen and thrombin ($500 to $1000 per dressing) prevents widespread deployment of this type of dressing. Quikclot® is a granular mineral zeolite that rapidly absorbs water in an exothermic reaction (Pusateri, A. E., et al., 2006). Some improvements on zeolite-impregnated dressings in the form of the kaolin-impregnated gauze (Quikclot® Combat Gauze) have been made. Bentonite (WoundStat™) also rapidly halts clotting (Ward, K. R., et al., J. Trauma, 63: 276-284 (2007); http://www.z-medica.com/zmedica/hemostasis_zmedica.asp). Kaolin and bentonite are clay minerals which act as sealants; however, they do not produce an exothermic reaction. It is also noteworthy that recently the relative thrombogenic effects of these aluminum phyllosilicate clay minerals have been examined and questioned for their in vivo safety (Kheirabadi, B. S., et al., J. Trauma Injury, Infection and Critical Care, 668: 2 (2010)). However, it is important to understand their mode of action as blood flow sealants and in clotting. Furthermore, considerable concern was registered about systemic vascular thrombogenesis shown by bentonite granules since the material was tested as loose granules at the locus of the wound bed and resulted in occlusive thrombi. HemCon®, which is principally chitosan, has strong tissue adhesive properties that seal the wound and stops bleeding through promotion of platelet aggregation (Pusateri, A. E., et al., 2006). TraumaDex employs starch microspheres which seal blood flow upon application through a molecular sieve-like mechanism (Gegel, B. T., AANA Journal, 78(2): 115-120 (2010)).

Nonwoven dressings are typically composite materials containing more than one fiber, component, or layer (Das, D., et al., Text. Prog., 44: 1-84 (2012); Doh, S., et al., Fibers Polym., 14: 2176-2184 (2013)). In recent years nonwoven medical dressings have increased in usage both for absorbent hemostatic and chronic wound applications (Abou-Okeil, A., et al., 2012; Parikh, D. V., et al., Int. Nonwovens J., 8: 24-28 (1999)). A variety of natural and synthetic fibers have been reported and are used to promote hemostasis, including cotton, viscose, rayon/polyester, glass filament, chitosan, nylon, wool, and alginate (Barnett, S. E., and S. J. Varley, Ann. R. Coll. Surg. Engl., 69: 153-155 (1987); Fischer, T. H., et al., J. Biomed. Mater. Res. B, 91: 381-389 (2009); Groth, T., and W. Wagenknecht, Biomaterials, 22: 2719-2729 (2001); Gu, R., et al., Biomaterials, 31: 1270-1277 (2010); Hutchinson, R., et al., Cellulose, 20: 537-545 (2013); Islam, S., et al., J. Biobased Mater. Bioenergy, 7: 439-443 (2013); Jayakumar, R., et al., Biotechnol. Adv., 29: 322-337 (2011); Palm, M. D., and J. S. Altman, J. Dermatol. Surg., 34: 431-445 (2008); Segal, H. C., et al., J. Biomater. Appl., 12: 249-257 (1998); van der Weyden, E. A., Br. J. Community Nurs., 2005,10, doi:10.12968/bjcn.2005.10.Sup2.18175; Wang, H., et al., Blood Coagul. Fibrinolysis, 18: 555-558 (2007)). Topical hemostatic agents consisting of proteinaceous materials like wool (Islam, S., et al., 2013), and collagen and fibrin (Raccuia, J. S., et al., Am. J. Surg., 163: 234-238 (1992)) have also been reported to be very effective in promoting clotting. However, natural hemostatic fibers may be made from polysaccharide fibers (Rathinamoorthy, R., and I. Sasikala, Int. J. Pharm. Sci., 3: 38-44 (2013)), some notable ones include oxidized regenerated cellulose (Hutchinson, R., et al., 2013), carboxymethylcellulose (Doh, S., et al., 2013; Wang, H., et al., 2007), N-acetyl-glucosamine (Fischer, T. H., et al., J. Biomed. Mater. Res. A, 80: 167-174 (2007); Fischer, T. H., et al., Biomed. Mater., 2008, 3, doi:10.1088/1748-6041/3/1/015009), and starch (Bellamy, R. F., 1984), and these may be incorporated into materials that constitute structurally or process modified polysaccharides fibers. These polysaccharide fibers have also played an important role in understanding the relationship of structure to function in the design of hemostatic dressings, and they have been examined for their structure/function relationships in contact activation of blood coagulation (Fischer, T. H., et al., 2009; Fischer, T. H., et al., 2007; Fischer, T. H., et al., 2008). Bleached cotton has been utilized as a hemostatic for several centuries, and has been a stable of the standard First Aid kit. However, the usage of unbleached cotton as a hemostatic dressing has scarcely been explored.

Greige cotton refers to unfinished cotton fibers that have not been scoured and bleached. The potential to use greige cotton in nonwoven absorbent products has received increased attention based on innovations in cotton cleaning and nonwovens processes that open and expose the hydrophilic cellulosic component of greige cotton fiber to water absorption.FIG. 1portrays a micrograph of hydroentangled greige cotton fibers that show how the outer layers of the fibers are loosened or lifted from the fiber during the hydroentanglement process. Previously it was shown that nonwoven greige cotton fibers, when compared with nonwoven bleached cotton, reduced the TEG (thromboelastography)-determined clotting time (FIG. 6) for both initial formation of fibrin and clot formation and increased the rate of clot formation while retaining approximately the same clot strength (Bellamy, R. F., 1984; Edwards, J. V., et al., A comparison of hemorrhage control and hydrogen peroxide generation in commercial and cotton-based wound dressing materials, IN Proceedings of 23rd Annual Meeting of the Wound Healing Society, SAWC Spring/WHS Joint Meeting, Silver (25th) Anniversary of the Wound Healing Society, Denver, Colo., 1-4 May 2013; Edwards, J. V., et al., J. Funct. Biomater., 5: 273-287 (2014)).

Moreover, recent work from USDA Agricultural Research Service in collaboration with H&H Medical has shown that nonwoven materials composed of greige cotton (True Cotton™ (TC)), and a combination of other fibers of varying polarity, accelerated blood clotting (Edwards, J. V., et al., A comparison of hemorrhage control and hydrogen peroxide generation in commercial and cotton-based wound dressing materials, IN Proceedings of 23rd Annual Meeting of the Wound Healing Society, SAWC Spring/WHS Joint Meeting, Silver (25th) Anniversary of the Wound Healing Society, Denver, Colo., 1-4 May 2013; Edwards, J. V., et al., 2014). It is important to note that TrueCotton™ is a highly cleaned form of raw cotton. Originally we found that TC accelerated clotting over bleached and scoured cotton as judged by thromboelastography (TEG) (Edwards, J. V., et al., 2014).

We have now studied materials that have been blended with combinations of greige cotton, bleached cotton, cellulosics, and synthetic fibers for the development of hemostatic wound dressings that would likely be suitable for accelerating clotting in the treatment of vascular trauma.

SUMMARY OF THE INVENTION

Disclosed herein are single layered nonwoven wound dressings containing (1) about 5% by weight to about 95% by weight (e.g., 5% to 95%) non-scoured, non-bleached greige cotton fibers (preferably about 30% by weight to about 80% by weight (30-80), more preferably about 50% by weight to about 60% by weight (50-60)), (2) about 5% by weight to about 95% by weight (e.g., 5% to 95%) bleached cotton fibers (preferably about 20% by weight to about 70% by weight (20-70), more preferably about 20% by weight to about 30% by weight (20-30)), and (3) about 5% by weight to about 60% by weight (e.g., 5% to 60%) hydrophobic fibers (e.g., polypropylene, nylon) (preferably about 5% by weight to about 50% by weight (5-50), more preferably about 5% by weight to about 20% by weight (5-20)); all percentages adding up to 100 wt %. Also, multi-layered nonwoven wound dressings, containing (1) at least one inner layer containing (a) about 50% by weight to about 95% by weight (e.g., 50% to 95) non-scoured, non-bleached greige cotton fibers (preferably about 60% by weight to about 80% by weight (60-80); more preferably about 50% by weight to about 60% by weight (50-60)) and (b) about 5% by weight to about 50% by weight (e.g., 5% to 50%) hydrophobic fibers (preferably about 20% by weight to about 40% by weight (20-40), more preferably about 40% by weight to about 50% by weight (40-50)), all percentages adding up to 100 wt %, and (2) at least one outer layer containing (a) about 5% by weight to about 95% by weight (e.g., 5% to 95%) non-scoured, non-bleached greige cotton fibers (preferably about 30% by weight to about 80% by weight (30-80), more preferably about 50% by weight to about 60% by weight (50-60)), (b) about 5% by weight to about 95% by weight (e.g., 5% to 95%) bleached cotton fibers (preferably about 20% by weight to about 70% by weight (20-70), more preferably about 20% by weight to about 30% by weight (20-30)), and (c) about 5% by weight to about 60% by weight (e.g., 5% to 60%) hydrophobic fibers (e.g., polypropylene, nylon) (preferably about 5% by weight to about 50% by weight (5-50), more preferably about 5% by weight to about 20% by weight (5-20)); all percentages adding up to 100 wt %.

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended as an aid in determining the scope of the claimed subject matter.

