WOUND DRESSING

Abstract

The present invention relates to wound dressings. In particular, the invention relates to antimicrobial wound dressings, methods of making the same and uses of the same. The wound dressing of the present invention comprises a wound contact layer and an absorption layer, wherein the wound contact layer comprises at least one antimicrobial agent and wherein the lateral wicking rate of the wound contact layer is the same or higher than the lateral wicking rate of the absorption layer. The wound dressing of the present invention provides an absorbent, conformable and anti-microbial medical device that may be used in a variety of medical situations, including post and/or pre-operative.

Claims

1. A wound dressing comprising a wound contact layer and an absorption layer, wherein the wound contact layer comprises at least one antimicrobial agent and wherein the lateral wicking rate of the wound contact layer is the same or higher than the lateral wicking rate of the absorption layer.

2. A wound dressing as claimed in claim 1, wherein the lateral wicking rate of the wound contact layer is from 0.1 to 20 seconds.

3. (canceled)

4. A wound dressing as claimed in claim 1, wherein the absorbency of the wound contact layer is less than the absorbency of the absorption layer and/or wherein the absorbency of the wound contact layer is less than 20 g/g.

5. (canceled)

6. A wound dressing as claimed in claim 1, wherein the wound contact layer comprises polyurethane foam and/or wherein the thickness of the wound contact layer is from around 0.5 to 4 mm.

7. (canceled)

8. A wound dressing as claimed in claim 1, wherein the wound contact layer is compressed and/or wherein the wound contact layer has a density of greater than 0.06 g/cm.sup.3, optionally wherein the wound contact layer is compressed to a width of from 20-90% of its original width.

9. (canceled)

10. A wound dressing as claimed in claim 1, wherein the antimicrobial agent is selected from the group consisting of silver, polyhexamethylene biguanide, chlorhexidine gluconate, chitosan, chitosan derivatives, octenidine, iodine and combinations of any two or more thereof.

11. (canceled)

12. A wound dressing as claimed in claim 1, wherein the absorption layer comprises an antimicrobial agent that is the same or different to the antimicrobial agent in the wound contact layer, optionally wherein the concentration of antimicrobial agent is higher in the wound contact layer than the absorption layer.

13. (canceled)

14. A wound dressing as claimed in claim 1, wherein the absorption layer swells by greater than 15% when fully saturated and/or wherein the absorption layer has a thickness of from 1 to 6 mm.

15. A wound dressing as claimed in claim 1, wherein the absorbency of the absorption layer is greater than 20 g/g; and/or wherein the absorption layer comprises polyurethane foam; and/or wherein the absorption layer is attached to the wound contact layer by an adhesive, optionally wherein the adhesive is acrylic based.

16-19. (canceled)

20. A wound dressing as claimed in claim 1, further comprising a backing layer, wherein the backing layer is optionally permeable to air and moisture but impermeable to water droplets and bacteria; and/or wherein the backing layer comprises a polyurethane film optionally having a thickness of from 10 to 100 microns.

21-23. (canceled)

24. A wound dressing as claimed in claim 1, further comprising a second absorption layer, wherein the second absorption layer optionally comprises a superabsorbent material; and/or further comprising a skin contact adhesive material attached to at least a portion of the wound contact layer, wherein the skin contact adhesive material optionally comprises an adhesive bonded to the carrier layer wherein the skin contact adhesive material optionally comprises a silicone adhesive bonded to a polyurethane film.

25-28. (canceled)

29. A method of manufacturing a wound dressing, the method comprising the steps of: a. attaching an wound contact layer to an absorption layer using an adhesive; and b. applying at least one antimicrobial agent to the wound contact layer; wherein the lateral wicking rate of the wound contact layer is the same or higher than the lateral wicking rate of the absorption layer.

30. A method as claimed in claim 29, wherein the adhesive comprises an acrylic powder, wherein the powder is scattered onto a surface of the wound contact layer and/or the absorption layer and the wound contact layer and the absorption layer are then laminated; and/or wherein the antimicrobial agent is applied to the wound contact layer as a solution.

31. (canceled)

32. A method as claimed in claim 29, further comprising the step of drying the wound dressing; and/or attaching a backing layer to the absorption layer using an adhesive; and/or attaching an adhesion means to the wound contact layer, the adhesion means comprising an adhesive bonded to a carrier layer.

33-34. (canceled)

35. A wound dressing as claimed in claim 1 for use as a medicament; or for use in killing or inhibiting the growth of microorganisms; or for use in absorbing fluid discharged from a physiological target or for use in stemming a flow of a fluid discharged from a physiological target site.

36-37. (canceled)

Description

[0142] Embodiments of the present invention will now be further described with reference to the following non-limiting examples and accompanying figures in which:

[0143] FIG. 1: is a representation of a wound dressing of the present invention;

[0144] FIG. 2: is a representation of an embodiment of a wound dressing of the present invention;

[0145] FIG. 3: is a representation of an embodiment of a wound dressing of the present invention;

[0146] FIG. 4: is a representation of an embodiment of a wound dressing of the present invention;

[0147] FIG. 5: is a graph showing the results of an elution test.

[0148] Referring to FIG. 1, there is shown a wound dressing (1) comprising a wound contact layer (2) and an absorption layer (3). The wound contact layer comprises an antimicrobial agent (not shown).

[0149] Typically, the wound contact layer (2) is a polyurethane open celled foam having a thickness of around 3 mm. The polyurethane foam can be compressed down to a thickness of 1.5 mm and/or can have a density of greater than 0.06 g/cm.sup.3. The absorption layer (3) is typically a polyurethane foam having a thickness of around 4 mm.

[0150] A distal surface of the wound contact layer (2) and a proximal surface of the absorption layer (3) are bonded to each other using an adhesive (not shown).

[0151] Referring to FIG. 2, there is shown a wound dressing (11) comprising a wound contact layer (12), an absorption layer (13) and a backing layer (14). The wound contact layer (12) and absorption layer (13) may be the same as those shown to in FIG. 1.

[0152] The backing layer (14) typically comprises a polyurethane film. The polyurethane film typically has a thickness of around 30 microns. The backing layer (14) is permeable to air and moisture vapour but is impermeable to microorganisms, such as bacteria, and liquid droplets, such as water. A distal surface of the absorption layer (13) and a proximal surface of the backing layer (14) are bonded to each other using an adhesive (not shown).

[0153] Referring to FIG. 3, there is shown a wound dressing (21) comprising a wound contact layer (22), an absorption layer (23), a backing layer (24) and a superabsorbent layer (25). The wound contact layer (22), absorption layer (23) and backing layer (24) may be the same as those described in FIG. 2.

[0154] The superabsorbent layer (25) typically comprises nonwoven fibrous material. The superabsorbent layer (25) is bonded to the absorption layer (23) and the backing layer (24) using an adhesive (not shown). The adhesive may be a heat bonded net.

[0155] Referring to FIG. 4, there is shown a wound dressing (31) comprising a wound contact layer (32), an absorption layer (33), a backing layer (34) and a skin contact adhesive layer (35). The wound contact layer (32), absorption layer (33) and backing layer (34) may be the same as those described in FIG. 2.

[0156] The skin contact adhesive layer (35) comprises a polyurethane film coated with a silicone adhesive. The film is perforated to as to allow for the passage of wound exudate into the wound contact layer (32).

[0157] The skin contact adhesive layer (35) is bonded to a proximal surface of the wound contact layer (32).

[0158] Table 1 shows changing density values for a 5 mm thick polyethylene foam compressed to three different thicknesses.

TABLE-US-00001 TABLE 1 Density (g/cm.sup.3) Min Max Thickness (mm) 0.07 0.09 4.5 0.22 0.28 1.5 0.33 0.43 1.0

EXAMPLES

Example 1

[0159] 3 mm thick open celled polyurethane foam wound contact layer was compressed to 1.5 mm and adhesive bonded to 4 mm thick polyurethane foam absorbent layer using an acrylic pressure sensitive adhesive. The polyurethane foam absorbent layer was then adhesive bonded to a polyurethane 30 micron film. A 20% BP CHG solution was dosed onto the wound contact layer and the dressing was heat treated to leave approximately 92 mg of CHG within the wound contact layer.

Example 2

[0160] 3 mm thick open celled polyurethane foam wound contact layer was compressed to 1.5 mm and adhesive bonded to 3.25 mm thick polyurethane foam absorbent layer using an acrylic pressure sensitive adhesive. The polyurethane foam absorbent layer was then adhesive bonded to a polyurethane 30 micron film. A 20% BP CHG solution was dosed onto the wound contact layer and the dressing was heat treated to leave approximately 92 mg of CHG within the wound contact layer.

Example 3

[0161] 1.5 mm thick open celled polyurethane foam wound contact layer was adhesive bonded to 4 mm thick polyurethane foam absorbent layer using an acrylic pressure sensitive adhesive. The polyurethane foam absorbent layer was then adhesive bonded to a polyurethane 30 micron film. A 20% BP CHG solution was dosed onto the wound contact layer and the dressing was heat treated to leave approximately 92 mg of CHG within the wound contact layer.

Example 4

[0162] 3 mm thick open celled polyurethane foam wound contact layer was compressed to 1.5 mm and adhesive bonded to 4 mm thick polyurethane foam containing approximately 0.13% Ag using an acrylic pressure sensitive adhesive. The polyurethane foam absorbent layer was then adhesive bonded to a polyurethane 30 micron film. A 20% BP CHG solution was dosed onto the wound contact layer and the dressing was heat treated to leave approximately 92 mg of CHG within the wound contact layer.

Example 5

[0163] 3 mm thick open celled polyurethane foam wound contact layer was compressed to 1.5 mm and adhesive bonded to 4 mm thick polyurethane foam containing approximately 0.13% Ag using an acrylic pressure sensitive adhesive. The polyurethane foam absorbent layer was then adhesive bonded to a polyurethane 30 micron film. A 20% BP CHG solution was dosed onto the wound contact layer and the dressing was heat treated to leave approximately 50 mg of CHG within the wound contact layer.

Example 6

[0164] 3 mm thick open celled polyurethane foam wound contact layer was compressed to 1.5 mm and adhesive bonded to 4 mm thick polyurethane foam absorbent layer using an acrylic pressure sensitive adhesive. The polyurethane foam absorbent layer was then adhesive bonded to a polyurethane 30 micron film. A chitosan lactate solution was dosed onto the wound contact layer and the dressing was heat treated to leave approximately 50 mg of chitosan lactate within the wound contact layer.

Example 7

[0165] 3 mm thick open celled polyurethane foam wound contact layer was compressed to 1.5 mm and adhesive bonded to 2.5 mm thick polyurethane foam absorbent layer using an acrylic pressure sensitive adhesive. The polyurethane foam absorbent layer was then adhesive bonded to a polyacrylate superabsorbent nonwoven material with a net heat bonded on the side distal to the wound surface. The superabsorbent material was then adhesive bonded to a polyurethane 30 micron film. A chitosan lactate solution was dosed onto the wound contact layer and the dressing was heat treated to leave approximately 92 mg of chitosan lactate within the wound contact layer.

Example 8

[0166] 3 mm thick open celled polyurethane foam wound contact layer was compressed to 1.5 mm and adhesive bonded to 3.25 mm thick polyurethane foam absorbent layer using an acrylic pressure sensitive adhesive. On a proximal side of the polyurethane foam wound contact layer was bonded a perforated silicone coated polyurethane film. The polyurethane foam absorbent layer was adhesive bonded to polyurethane 30 micron film. A 20% BP CHG solution was dosed onto the wound contact layer and the dressing was heat treated to leave approximately 92 mg of CHG within the wound contact layer.

[0167] Test Methods

[0168] Absorbency:

[0169] An area of a test wound dressing is cut to 50×50 mm size and weighed. The test wound dressing is then fully immersed in saline solution for 30 minutes. After 30 minutes, the test wound dressing is removed by a corner of the dressing and allowed to drain for 15 seconds. The test wound dressing is then re-weighed and the fluid increase based on g/g calculated.

[0170] Wicking Rate:

[0171] An area of a test wound dressing is cut to 50×50 mm size. 2 g of saline solution is measured and pipetted onto the surface of the test article. The time taken for the 2 g of saline solution to be absorbed into the test article is recorded.

[0172] Comparative Testing

[0173] The wound dressing of the present invention was tested in comparison to Biopatch®, an antimicrobial dressing currently available on the market. The results are explained below.

[0174] A wound dressing of the present invention was prepared according to Example 2.

[0175] The wound dressing of the present invention comprised a 25 mm diameter disc comprising a central 4 mm hole and radial slit extending from the central hole to the edge of the disc.

[0176] For comparison purposes, a Biopatch® disc was obtained having a diameter of 25 mm comprising a central 4 mm hole and radial slit extending from the central hole to the edge of the disc.

TABLE-US-00002 TABLE 2 Absorbency: Example 2 test dressing >10.0 g/g Biopatch ®  >8.0 g/g

TABLE-US-00003 TABLE 3 Antimicrobial content: Example 2 test dressing 87 +/− 2 mg Biopatch ® 89 +/− 2 mg

[0177] Elution Test:

[0178] An elution test was method devised to assess the level of CHG eluted from the each test dressing. The higher the elution value, the more CHG is being delivered to the microorganisms at the wound interface and within the wound dressing, the theory being that the more antimicrobial agent that can be exposed to the microorganisms, the greater the kill rate.

[0179] The aim of the test method is to determine the elution profile from the CHG impregnated test materials.

[0180] The following test method was followed: [0181] (1) bond test wound dressing to a 30 mm diameter disc of Corex, backing membrane side down, to prevent the test wound dressing from curling throughout testing; [0182] (2) wet a filter paper disc with 0.4 ml of deionised water; [0183] (3) place the test wound dressing onto the filter paper; [0184] (4) place the test wound dressing/filter paper inside a foil pouch, ensuring that the filter paper remains in contact with the entire surface of the wound contact layer side of the wound dressing; [0185] (5) seal the pouch using a vacuum, to maintain contact between the filter paper and surface of the wound dressing; [0186] (6) store the wound dressings at ambient conditions; [0187] (7) at the required time interval carefully open the pouch & remove the test wound dressing/filter paper; [0188] (8) remove the filter paper from beneath the test wound dressing; [0189] (9) submerge the filter paper in a set amount of deionised water; [0190] (10) leave the filter paper submerged for 60 minutes; [0191] (11) measure the conductivity reading of the solution; [0192] (12) record the result; [0193] (13) repeat steps 3-12, using the same test article, at further time intervals; [0194] (14) calculate the amount of CHG (mg) from Conductivity (μS/cm) at the different time points.

[0195] The results of the testing are shown in FIG. 5 and Table 4 below.

TABLE-US-00004 TABLE 4 Cumulative elution CHG (mg) over time Time Point (hrs) Sample Type 2 24 48 72 96 120 144 168 Example 2 test dressing 29.82 45.05 55.16 61.58 66.13 69.94 72.72 74.67 Example 2 test dressing 28.20 42.60 52.16 58.23 62.54 66.14 68.77 70.61 with 7 mm centre hole Composition as in Example 17.57 26.54 32.49 36.27 38.95 41.20 42.84 43.98 2 but as a 19 mm disc with 1.5 mm centre hole and radial slit Biopatch ® 2.55 5.67 13.31 20.15 24.63 28.33 31.19 33.44

[0196] It is clear from the Table 4 and from FIG. 5 that the Biopatch® dressing releases CHG at a far slower rate, around 10× slower, than the dressing of the present invention. As such, the dressing of the present invention is beneficial for application to wounds where a large quantity of antimicrobial agent needs to be delivered quickly.

[0197] It is of course to be understood that the present invention is not intended to be restricted to the foregoing examples which are described by way of example only.