WO2013085891A1

WO2013085891A1 - Fast curing polymeric sealant for negative pressure wound therapy

Info

Publication number: WO2013085891A1
Application number: PCT/US2012/067738
Authority: WO
Inventors: Xianbo Hu
Original assignee: Avery Dennison Corporation
Priority date: 2011-12-09
Filing date: 2012-12-04
Publication date: 2013-06-13

Abstract

Fast curing polymeric sealing materials are described. The sealing materials are useful for sealing in negative pressure wound therapies, such as between a biological surface and a drape or other covering. Also described are sealed systems including the sealing materials, and methods of sealing using the sealing materials.

Description

FAST CURING POLYMERIC SEALANT FOR NEGATIVE PRESSURE WOUND THERAPY

Cross References to Related Applications

[0001] This application claims the benefit of U.S. Provisional Patent Application no. 61/568,830 filed December 9, 2011, which is incorporated herein by reference in its entirety.

Background

[0002] The present subject matter relates to polymeric sealing materials used in negative pressure wound therapies to seal or prevent leaks from occurring between the wound environment and the external environment.

Summary

[0003] The difficulties and drawbacks associated with previously known technology are addressed in the present systems and methods for creating and maintaining sealed wound environments in negative pressure wound therapies.

[0004] In one aspect, a system is provided for creating or maintaining a sealed environment about an external wound area accessible along a patient's skin. The system comprises a flexible drape disposed over the wound area, and a fast curing polymeric sealing material disposed between the drape and the patient's skin such that a sealed environment is formed about the wound area.

[0005] In another aspect, a method is provided for creating or maintaining a sealed environment about an external wound area accessible along a patient's skin. The method comprises providing a flexible drape, and covering a wound area of a patient with the drape. The method also comprises providing a fast curing polymeric sealing material. The method additionally comprises administering an effective amount of the polymeric sealing material between the drape and the patient's skin about the wound area so as to form a closed region about the wound area. And, the method comprises curing the polymeric sealing material.

[0006] As will be realized, the subject matter described herein is capable of other and different embodiments and its several details are capable of modifications in various respects, all without departing from the claimed subject matter. Accordingly, the description is to be regarded as illustrative and not restrictive.

Detailed Description of the Embodiments

[0007] The present subject matter relates to polymeric sealing materials that are used in negative pressure wound therapies (NPWT) to seal or prevent leaks from occurring between the wound environment and the external or ambient environment. The polymeric sealing materials can be used along the interface between a user's skin and a drape or other covering associated with the NPWT assembly. And so, in certain embodiments the polymeric sealing materials are preferably compatible with biological skin. The polymeric material is initially flowable so that it can be administered as desired, such as by applying onto a user's skin or at one or more regions of a NPWT covering where leaks occur, or are expected to occur. The polymeric sealing material then quickly cures and effectively seals the area(s) of interest.

Negative Pressure Wound Therapy

[0008] Negative pressure wound therapy (NPWT) is a therapeutic technique using a vacuum dressing to promote healing in acute or chronic wounds and enhance healing such as for first and second degree burns. Typically, the wound is an external wound accessible along a patient's skin. The therapy involves the controlled application of sub-atmospheric pressure to the local wound environment, using a sealed wound dressing connected to a vacuum pump.

[0009] NPWT promotes wound healing by applying a vacuum through a special sealed dressing. The continued vacuum draws out fluid from the wound and increases blood flow to the area. The vacuum may be applied continuously or intermittently, depending on the type of wound being treated and the clinical objectives. Typically, the dressing is changed two to three times per week. The dressings used for the technique include open-cell foam dressings and gauze, sealed with an occlusive dressing intended to contain the vacuum at the wound site. Where NPWT devices allow delivery of fluids, such as saline or antibiotics to irrigate the wound, intermittent removal of used fluid supports the cleaning and drainage of the wound bed.

[0010] A general technique for NPWT is as follows. A dressing is fitted to the contours of a wound and sealed with a transparent film or "drape" as known in the art. A drainage tube is connected to the dressing through an opening in the transparent film. The drainage tu be is also connected to a vacuum source, turning an open wound into a controlled, closed wound while removing excess fluid from the wound bed to enhance circulation and remove wound fluids. This creates a moist healing environment and reduces edema. The technique is usually used with chronic wounds or wounds that are expected to present difficulties while healing, such as those associated with diabetes.

[0011] Commercial products for the technique are generally divided into three categories based upon the type of dressing used over the wound surface: open-cell foam, gauze, or honeycombed or non-woven textiles with a dimpled wound contact surface. Foam dressings are used to fill open cavity wounds and can be cut to size to fit wounds. The foam dressing is applied, filling the wound and then a film drape is applied over the top to create a seal around the dressing. A vacuum tube is connected through an opening in the film drape to a canister on the side of a vacuum pump. NPWT can be conducted using standard medical supplies such as open weave cotton gauze, transparent film, a flat drain and tubing that connects to a vacuum pump. The flat drain is sandwiched in gauze and this is then placed onto the wound. A film drape is used to cover the wound and create a complete seal, and then the drain is connected to the pump via the tubing. The third type of dressing involves layers of non- woven polyester, joined by a silicone elastomer, and has a non-adherent wound contact surface made up of numerous small semi-rigid dome structures.

[0012] With all three techniques, once the dressing is sealed the vacuum pump can be set to deliver continuous or intermittent pressures, with levels of pressure depending on the device used varying between from about -125 to about -75 mm Hg depending on the material used and patient tolerance. Pressure can be applied constantly or intermittently.

[0013] The dressing type used depends on the type of wound, clinical objectives and patient. For pain sensitive patients with shallow or irregular wounds, wounds with undermining or explored tracts or tunnels, gauze may be used, while foam may be cut easily to fit a patient's wound that has a regular contour and perform better when aggressive granulation formation and wound contraction is the desired goal.

Polymeric Sealing Materials

[0014] As noted, polymeric sealing materials are provided to create and maintain a reduced or sub-atmospheric pressure around a wound area. The polymeric sealing material is typically disposed along the interface of the drape or covering for the wound and the patient's skin. Generally, nearly any polymeric sealing material can be used so long as (i) the material exhibits fast curing or fast polymerizing characteristics; (ii) after curing, the sealing material is flexible and pliable; (iii) after curing, the sealing material will sufficiently adhere to a biological surface such as human skin; and (iv) the sealing material should exhibit debonding characteristics which do not cause excessive pain or discomfort to the user. Each of these aspects is described in greater detail as follows.

[0015] Polymeric sealing materials can be categorized as either chemical curing systems or physical curing systems. In a typical chemical curing system, the system contains a polymeriza ble monomer, oligomer, or macromer, or a mixture thereof with or without solvent, and crosslinker and initiators capa ble of initiating free radical polymerization. The monomer, oligomer and/or macromer have polymeriza ble groups which typically include but are not limited to (meth)acrylamide, (meth)acrylate, styryl, vinyl ester, vinyl ketone, vinyl ethers, etc. In certain aspects it is particularly desira ble to use ethylenically unsaturated functiona l groups. Suita ble crosslinkers include crosslinkers having at least two polymeriza ble groups. The initiation of the curing or polymerizing can be induced by thermal means, light mea ns, via a redox reaction, or by atom transfer polymerization. Initiation of curing or polymerizing ca n be initiated by nearly a ny suita ble method or strategy. Another example of chemical curing is through Michael addition and "Click-Chemistry" as known in the art. Click-Chemistry is chemistry tailored to generate su bstances quickly and relia bly by joining small units together.

[0016] Typical physical curing may include, but is not limited to, complexation, hydrogen bonding, desolvation, Van der wals interactions, and ionic bonding.

[0017] Certain polymeric systems can be either chemically cured or polymerized, or may be physically cu red or polymerized. An example of such a system is a hydrogel system as follows. A hydrogel is a hydrophilic polymer network which can be crosslinked either physically and/or chemically. Due to the excellent biocompatibility and similar physical properties to soft tissue, hydrogel systems have been widely explored and developed recently for applications in contact lenses, biosensors, wound dressings, drug delivery, a nd tissue engineering. Two different hydrogel systems are described herein as examples of polymeric sealing materials which could be used in negative pressure wound therapy. An example of chemical curing a hydrogel system via a redox system is as follows. A hydrogel can be easily formed by mixing monomer/oligomer/macromer with one or more reducing agents and monomer/oligomer/macromer with one or more oxidizing agents. An example of physical curing of a hydrogel is as follows. Hydrogels can be formed by the ionic interaction of divalent cationic metal ions (such as Ca⁺²) with ionic polysaccharides such as alginates, xanthan gums.

[0018] A fast curing polymeric sealing system can be applied in a NPWT application using a variety of techniques. In certain embodiments in which the sealing system includes two reactive components, the application of a fast curing polymeric system is performed using a d ual syringe. The dual syringe keeps the two reactive components apart until delivery. During application, a static mixing tip mixes the two components uniformly and initiates the curing or polymerizing to form the polymeric layer. A tip capable of forming a stream or mist, or a brush shaped tip can be used to form a uniform layer. In many embodiments, the polymeric sealing material is applied between a drape or other flexible covering and a patient's skin, around the wound area of interest. If the polymeric sealing material is applied in a layer, the thickness of the layer depends upon the parameters of the NPWT system and aspects of the wound area. Typically, the layer of sealing material is from about 0.01 mm to about 10 mm in thickness. In certain embodiments, the thickness of the sealing material layer is from about 0.05 mm to about 5 mm. And, in still other embodiments, the thickness of the sealing material is from about 0.1 mm to about 2.5 mm.

[0019] In certain embodiments, a method for creating or maintaining a sealed environment about an external wound area accessible along a patient's skin is as follows. The method generally comprises providing a flexible drape. The drape can be any suitable flexible covering known in the medical field, and particularly those designed for NPWT applications. The method also comprises covering a wound area of a patient with the drape. The method further comprises providing a fast curing polymeric sealing material. The sealing material can be any of the sealing materials as described herein. The method also comprises administering an effective amount of the polymeric sealing material between the drape and the patient's skin about the wound area so as to form a closed region about the wound area. As will be appreciated, the closed region will define the region of reduced pressure. The method also comprises curing the polymeric sealing material. Curing can be performed by any of the techniques or strategies described herein.

[0020] As noted, an aspect of the polymeric sealing material is that the material exhibits fast curing or polymerization. The term "cure time" as used herein refers to the time from contacting the user's skin or other covering associated with the NPWT assembly until the time at which the material becomes non-flowable. In certain embodiments, it is desirable that the sealing material exhibit relatively fast curing characteristics. If the cure time is too long, excessive run-off of the liquid may occur to undesired areas and subsequent curing may also occur at those areas. This may result in adverse effects. The term "fast curing" refers to the polymeric sealing material curing in a time period less than 5 minutes. In certain embodiments, the cure time is in the range of from about 1 second to about 5 minutes. In other embodiments, the cure time is from about 2 seconds to about 1 minute. And in still other embodiments, the cure time is from about 5 seconds to about 30 seconds. [0021] Another aspect of the polymeric sealing material is that after curing, the sealing material will be relatively flexible and pliable. This ensures that the material will bend and flex as necessary such as during movement by the patient, so that the seal is maintained.

[0022] After curing, the sealing material will sufficiently adhere to a biological surface such as skin so as to maintain the seal. Specifically, after curing, the sealing material will adhere to the skin with an appropriate adhesive strength for use in NPWT applications, and specifically for maintaining a seal between a drape and patient skin. The removal of the cured sealing materials will be similar to or even easier than the removal of a typical NPWT drape. No additional solvent or release agent will be needed to debond the material.

[0023] In certain embodiments, it is also desirable that the polymeric sealing material be sticky or tacky. However, in certain other embodiments, the polymeric sealing material is not sticky or tacky.

[0024] In certain embodiments, preferred polymeric sealing materials are those described in US Patent Application Publication 2002/0122771. In still other embodiments, a preferred polymeric sealing material is a wound spray dressing such as HYD OME 6-TS-66M Massive Wound Spray Dressing commercially available from Hydromer, Inc. of Branchburg, New Jersey.

[0025] Advantages of the preferred embodiment fast curing polymeric sealing material are numerous and include the following. The preferred embodiment sealing materials provide a single solution for all potential leakage. The material seals not only the interface between skin and drape of a NPWT system, but also seals any other connection/junction for potential leakage. Another advantage relates to a filling and sealing function of the material. Due to the fast curing time, the material can fill all, or substantially all, potential leaking pathways such as channels, microchannels, wrinkles, and then cures to seal such pathways. Additional advantages include excellent ability to conform to all anatomic sites, no requirements in modifying existing NPWT equipment or components, ease in application, does not hinder body movements, and the adhesion properties can be easily adjusted by either physical or chemical methods.

[0026] Many other benefits will no doubt become apparent from future application and development of this technology.

[0027] All patents, applications, and articles noted herein are hereby incorporated by reference in their entirety. [0028] As described hereinabove, the present subject matter overcomes many problems associated with previous strategies, systems and/or devices. However, it will be appreciated that various changes in the details, materials and arrangements of components, which have been herein described and illustrated in order to explain the nature of the present subject matter, may be made by those skilled in the art without departing from the principle and scope of the claimed subject matter, as expressed in the appended claims.

Claims

Claims What is claimed is:

1. A system for creating or maintaining a sealed environment about an external wound area accessible along a patient's skin, the system comprising:

a flexible drape disposed over the wound area; and

a fast curing polymeric sealing material disposed between the drape and the patient's skin such that a sealed environment is formed about the wound area.

2. The system of claim 1 wherein the polymeric sealing method cures in a time period of from about 1 second to about 5 minutes.

3. The system of claim 1 wherein the polymeric sealing material cures in a time period of from about 2 seconds to about 1 minute.

4. The system of claim 1 wherein the polymeric sealing material cures in a time period of from about 5 seconds to about 30 seconds.

5. The system of any one of claims 1-4 wherein the polymeric sealing material is a hydrogel system.

6. A method for creating or maintaining a sealed environment about an external wound area accessible along a patient's skin, the method comprising:

providing a flexible drape;

covering a wound area of a patient with the drape;

providing a fast curing polymeric sealing material;

administering an effective amount of the polymeric sealing material between the drape and the patient's skin about the wound area so as to form a closed region about the wound area;

curing the polymeric sealing material.

7. The method of claim 6 wherein curing is performed in a time period of from about 1 second to about 5 minutes.

8. The method of claim 6 wherein curing is performed in a time period of from about 2 seconds to about 1 minute.

9. The method of claim 6 wherein curing is performed in a time period of from about 5 seconds to about 30 seconds.

10. The method of any one of claims 6-9 wherein administering the polymeric sealing material includes forming a layer of the sealing material between the drape and the patient's skin.

11. The method of claim 10 wherein the layer has a thickness of from about 0.01 mm to about 10 mm.

12. The method of claim 10 wherein the layer has a thickness of from about 0.05 mm to about 5 mm.

13. The method of claim 10 wherein the layer has a thickness of from about 0.1 mm to about 2.5 mm.