Patent Publication Number: US-2007122462-A1

Title: Bandage with a hydrophilic foam containing silver

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims the benefit of U.S. Provisional Application No. 60/680,225 filed May 12, 2005. 
    
    
     FIELD OF THE INVENTION  
      This invention is directed generally to an antibiotic bandages, and more particularly to wound dressing bandages that foster a moist wound-healing environment while minimizing the possibility of infection.  
     BACKGROUND  
      Silver has been used as an antimicrobial since ancient times. Recent years have seen a renewed interest in silver as an antibiotic. This renewed interest is driven in part by the development of antibiotic-resistant bacteria, such as methicillin-resistant  Staphylococcus aureus  (MRSA). Resistant bacteria are especially problematic in wounds. Silver is a broad-spectrum antibiotic that is effective against such resistant bacteria and bacteria do not appear to develop resistance to silver. There is an urgent need for an antibiotic wound care product that uses silver to treat and/or prevent MSRA and other resistant infections.  
      Silver is also known to exhibit wound-healing properties. Expeditious wound healing benefits the patient in terms of increased comfort and decreased susceptibility to infection and secondary injury. There is a need for wound care products that utilize silver to increase the rate of wound healing.  
      Many presently existing antibiotic wound care products lose their antibiotic activity in a short period of time. This is especially true for wound care products that contain silver in an ionic form. Ionic silver is readily dissolved in an aqueous environment and dissipated. Such dressings must be replaced frequently often resulting in extreme pain or discomfort and inconvenience for the patient as the dressing is removed and a new dressing is applied. Similarly, silver creams (including silver sulfadiazine) must be consistently reapplied to the injured area, and the dressing must be removed for reapplication of the cream. There is a need for a wound care product that releases silver ions over an extended period of time and which alleviates the need for frequent removal or replacement of the dressing or application of silver creams.  
      Silver is commonly applied in as a silver salt. Such salts can be irritating to the skin. There is a need for a non-irritating silver wound care product that does not rely on silver salts for the delivery of silver ions. Moreover, prolonged contact with silver salts can cause argyria, which creates a pronounced, permanent ashen-gray skin discoloration that can be localized or universal. Thus, there is a need for a silver wound care product that does not cause argyria.  
      Silver is known to affect the operation of matrix metalloproteinases (MMPs). Excessive MMPs are known to interfere with wound healing. Excessive interference with MMPs can also interfere with wound healing. Presently existing silver-based wound care products often inhibit MMPs too much, thereby interfering with the wound healing process. Thus, there is a need for a silver wound care product that delivers an amount of silver, which limits the activity of MMPs without unduly restricting MMP activity.  
     SUMMARY OF THE INVENTION  
      This invention is directed to a bandage formed from one or more layers of a stretchable, textile material forming a body of the bandage. The bandage may include a base material attached to the stretchable, textile material on a first side. In at least one embodiment, the base material may be a hydrophilic foam attached to the stretchable, textile material on a first side. A silver material may be attached to the hydrophilic foam for reducing risk of infection. The bandage may create a moist environment that is optimum for the release of silver ions into the wound bed to reduce the risk of infection in a wound on a patient.  
      The body of the bandage may include silver coated fibers. The silver coated fibers may be formed from silver coated nylon fibers. The base material may also include a silver material formed from a silver hydroxide or a silver powder, or both, that is attached to the base material for reducing risk of infection. The silver coated fibers, the silver hydroxide powder, or the silver powder may be used in amounts of about 0.5 percent and 10 percent by weight of the hydrophilic foam.  
      The silver material may be attached to a surface of the hydrophilic foam forming an antimicrobial layer on an outer surface of the bandage. In another embodiment, the silver material may be added to the base material during formation of the base layer. In such a configuration, the silver material may be positioned throughout the base material for increased antimicrobial effects.  
      An advantage of this invention is that the bandage may be formed from a silver metallized chopped fiber, a specialized metallic silver powder and silver hydroxide to provide ionic silver to treat and/or prevent MSRA and other resistant bacteria and fungi.  
      Another advantage of this invention is that the bandage uses ionic silver to inhibit the growth of bacteria that is detrimental to wound healing.  
      Yet another advantage of this invention is that the bandage includes ionic silver to increase the rate of wound healing and releases silver ions over a period of time. The release of silver ions is non-irritating and does not rely on silver salts for the delivery of silver ions.  
      Another advantage of this invention is that the bandage does not cause argyria in a patient to which the bandage is attached.  
      Still another advantage of this invention is that the bandage creates and maintains a moist wound-healing environment while preventing the growth of bacteria and fungi;  
      Another advantage of this invention is that the bandage maintains a moist environment, but eliminates unpleasant odors.  
      Yet another advantage of this invention is that the bandage uses metallic silver with a relatively large surface area that does not become detached from the base material.  
      Another advantage of this invention is that the bandage enables the delivery of an optimal dosage of silver ions.  
      Still another advantage of this invention is that the bandage delivers an amount of silver that limits the activity of MMPs without unduly restricting MMP activity.  
      Another advantage of this invention is that the bandage is easy and inexpensive to manufacture.  
      These and other embodiments are described in more detail below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The accompanying drawings, which are incorporated in and form a part of the specification, illustrate embodiments of the presently disclosed invention and, together with the description, disclose the principles of the invention.  
       FIG. 1  is a perspective view of a bandage having aspects of this invention.  
       FIG. 2  is a cross-section of the bandage taken at line  2 - 2  in  FIG. 1 .  
       FIG. 3  is a perspective view of a sliver coated fiber.  
       FIG. 4  is a perspective view of an alternative bandage having aspects of this invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      As shown in  FIGS. 1-4 , this invention is directed to a bandage  10  formed from one or more layers of a stretchable, textile material  12  forming a body  14  of the bandage  12 . The bandage  10  may include a base material  16  attached to the stretchable, textile material on a first side. In at least one embodiment, the base material  16  may be a hydrophilic foam attached to the stretchable, textile material  12  on a first side. A silver material  18  may be attached to the hydrophilic foam for reducing risk of infection. The bandage  10 , and specifically, the hydrophilic foam, may create a moist environment that is optimum for the release of silver ions into the wound bed to reduce the risk of infection in a wound on a patient.  
      As shown in  FIG. 2 , the bandage  10  may be formed from a textile material  12 . The textile material  12  may be a compression stretch bandage. The textile material may be any appropriate material. In at least one embodiment, the bandage  10  may include silver coated fibers  20 , as shown in  FIG. 3 , attached to the textile material  12 . The silver coated fibers  20  may be manufactured as described in U.S. Pat. No. 4,042,737, entitled “Process for producing crimped metal-coated filamentary materials, and yarns and fabrics obtained therefrom,” issued to Rohm and Haas Company (Philadelphia, Pa.), on Aug. 16, 1977, and are commercially available from Noble Fiber Technologies under the tradename X-STATIC. The silver coated fiber  20  may also be created in accordance with the process disclosed in U.S. patent application Ser. No. 10/666,568, the disclosure of which is hereby incorporated by reference.  
      The silver coated fiber  20  may be formed from a silver-coated nylon fiber. The following table describes characteristics of the silver coated fibers  20 :  
                                                       Length   Denier   Silver           in Mils   (dpf)   (% w/w)                                                            Outside range   80-200   .5-50   3-75%           Intermediate range   40-150   .7-30   9-60%           Optimal range   30-100    1-10   12-30%            Ideal   ˜20   ˜3   ˜18                      
 
      The silver material  18  may also be formed from a silver hydroxide. The silver hydroxide may be prepared as described in U.S. patent application Ser. No. 10/937,966, the disclosure of which is hereby incorporated by reference. In another embodiment, the silver material  18  may be a silver micro and nano powder. The silver micro and nano powder may be prepared as described in U.S. patent application Ser. No. 10/937,966. The above obtained powder may be surface modified if a need for a greater ion release exists for a particular application. This may be done as described in U.S. patent application Ser. No. 10/836,530, which is hereby incorporated by reference.  
      The percentage of the silver material  18  used together with the base material  16  may be controlled. In particular, the percentage of silver material  18  may be controlled by controlling the percentage of silver coated fibers  20  and silver powder added to the base material  16 . In addition, the viscosity of the liquid inside the foam may be kept constant. The amount of silver material  18  used may also be controlled by altering the viscosity but keeping the percentage of silver coated fibers  20  or silver powders, or both the same.  
      The base material  16  may be a hydrophilic foam. The foam may be a chemically formed hydrophilic based polyurethane foam. The foam may have a thickness between about 0.1 inches and about 0.5 inches. The hydrophilic foam may be mixed with any of the three mentioned silver materials or any combination of the silver materials. The hydrophilic foam with silver coated fibers  20  can be prepared using materials in the following percentages:  
                                                       Percent of X-Static by weight           Type of Silver Material   by volume                          Chopped fiber (20 mil × 3 dpf)   0.5-10           Silver hydroxide powder   0.5-10           Silver powder with surface   0.5-10           conversion           Silver powder w/o surface   0.5-10           conversion                      
 
 Thus, the silver coated fibers  20  may be used in amounts of chopped fibers of between 0.5 percent and 10 percent by weight of the hydrophilic foam  16 . The silver hydroxide powder may be used in amounts of about 0.5 percent and 10 percent by weight of the hydrophilic foam  16 . The silver powder may be used in amounts of about 0.5 percent and 10 percent by weight of the hydrophilic foam  16 . These materials create a flexible, stretchable and hydrophilic bandage  10 . The moisture filled foam  16  with the silver material  18  provides an optimum moist environment which enables an optimum release of silver ions into a wound to increase a healing rate without significant scarring. 
 
      The silver material  18  may be attached to an outer surface of the base material  16 , referred to as metallizing the base material  16 , as shown in  FIGS. 1-2 , or may be incorporated in the base material  16  during formation of the base material  16 , as shown in  FIG. 4 . The silver material  18  may be attached to the base material  16  via metallizing using, for instance, the process disclosed in U.S. patent application Ser. No. 11/209,567, which is incorporated by reference herein, whereby the silver material  18  forms a layer of silver on the base material  16 . In another embodiment, the silver material  18  may be included in the base material  16  during formation of the base material  16 . By including the silver material  18  in the base material  16 , the silver material  18  may found throughout the base material  16  and not limited to being only on the surface of the base material.  
      The bandage  10  includes resistance at levels recordable in Ohms, which was an unexpected result. The foam  16  was conductive not only in the X and Y direction but also in the Z direction, which indicates that the foam  16  together with the silver material  18  have thermodynamic characteristics. It should be noted that lack of conductivity does not impair the ion release or the anti-microbial efficacy of the bandage  10 .  
     EXAMPLE  
      The base material  16  may be formed from a hydrophilic foam and a chopped fiber having about a 20 mil length and 3 dpf that was blown together. In another embodiment, the base material  16  may be formed from a hydrophilic foam and a silver hydroxide and silver powder, as noted below. The hydrophilic foam may have a dark brown color that darkens as time passes due to the hydroxide in the silver. However, the antimicrobial capabilities of the hydrophilic foam do not deteriorate with time. The following data was obtained from experiments:  
                                                           Ion                           release               after 1       ASTM   ASTM           %   hour (In-   Resistance   E-2149   E-2140       Foam   of X-   house   of sample in Z   against  S. Aureaus     against       blown with   Static   protocol)   direction   (1 hr)   MRSA (1 hr)                                                        Chopped   4   9   1 × 10 5  Ω   99.9%   99.9%       fiber (20 mil × 3 dpf)       Chopped   2   5   1 × 19 5  Ω   99.9%   99.9%       fiber (20 mil × 3 dpf)       Silver   3   10   1 × 10 8  Ω   99.9%   99.9%       hydroxide*       Silver   5   18   1 × 10 7  Ω   99.9%   99.9%       hydroxide*       Surface   5   25   1 × 10 5  Ω   99.9%   99.9%       converted silver       X-Static powder       Surface   3   20   1 × 10 5  Ω   99.9%   99.9%       converted silver       X-Static                  
 
      According to another test, the degree of hydrophilicity of the base material  16  was affected little by the addition of the silver material  18  that was added, as shown below:  
                              Hydrophilicity Test (Based on Water retention Capacity)                                     Foam w/5% Ag   Foam w/out Ag                       Orginal Length   81 ± 2.0 mm   81 ± 2.0 mm           Original Width   60 ± 2.0 mm   60 ± 2.0 mm           Original Thickness   6.2 ± 0.8 mm    6.2 ± 0.8 mm            H 2 O Held   16 ml   16 ml           Wt. After       mins.            0   11.922    11.042             30   7.606   6.624            45   6.448   5.348            60   5.420   4.170            75   4.500   3.216            90   3.943   2.641           105   3.738   2.433                         Oven Temp 100° C.                5.22% silver on the foam             
 
     
       
     
      While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular embodiments disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.