WOUND DRESSING

Abstract

The present invention relates to materials for use as or in wound dressings. In particular, the present invention relates to a multilayer material for use as or in a wound dressing and to methods of making the multilayer material. The multilayer material comprises first and second layers comprising a chitosan and/or a chitosan derivative and a third layer located between the first and second layers comprising a reinforcing material, wherein one or more of the layers further comprises a physiologically acceptable acid.

Claims

1. A multilayer material comprising first and second layers comprising a chitosan and/or a chitosan derivative and a third layer located between the first and second layers comprising a reinforcing material, wherein one or more of the layers further comprises a physiologically acceptable acid.

2. A multilayer material according to claim 1, wherein the physiologically acceptable acid is located in either the first and/or second layer of the multilayer material.

3. A multilayer material according to claim 1, wherein the physiologically acceptable acid is located in the third layer of the multilayer material.

4. A multilayer material according to claim 1, wherein the first and/or second layers further comprise a carrier material for the acid.

5. A multilayer material according to claim 4, wherein the acid is absorbed in, or coated onto, the carrier material.

6. A multilayer material according to claim 1, wherein the reinforcing material comprises a non-absorbent material, for example viscose.

7. A multilayer material according to claim 1, wherein the reinforcing material comprises an absorbent material.

8. A multilayer material according to claim 7, wherein the absorbent material is a superabsorbent material.

9. A multilayer material according to claim 8, wherein the superabsorbent material is a polymeric material, such as poly(vinyl alcohol) (PVA), poly(ethylene oxide) (PEO), and poly(acrylic acid).

10. A multilayer material according to claim 1, wherein the chitosan, chitosan derivative and/or the reinforcing material are in the form of fibres.

11. A multilayer material according to claim 1, wherein the chitosan derivative is a partially deacetylated chitin, optionally with a deacetylation of degree above about 50%.

12. A multilayer material according to claim 1, wherein the physiologically acceptable acid comprises an organic acid selected from formic acid, acetic acid, ascorbic acid, halogen acetic acids (such as fluoro- or chloroacetic acid), propanoic acid, propenoic acid, lactic acid, succinic acid, acrylic acid, glyoxylic acid, pyruvic acid, hydroxyl propionic/butanoic acid and combinations of any two or more thereof.

13. A multilayer material according to claim 12, wherein the organic acid is lactic acid.

14. A multilayer material according to claim 1, wherein the acid is coated onto the chitosan, chitosan derivative, carrier material and/or the reinforcing material.

15. A multilayer material according to claim 1, wherein the first and second layers both comprise chitosan fibres coated with lactic acid; and the third layer comprises poly(acrylic acid) fibres.

16. A multilayer material according to claim 1, wherein the multilayer material comprises first and second layers comprising chitosan fibres, wherein the first and/or second layer further comprises a carrier material having lactic acid coated thereon; and a third layer comprising poly(acrylic acid) fibres.

17. A wound dressing comprising a multilayer material according to claim 1.

18. A method of manufacturing a multilayer material comprising the steps of: (a) providing first and second layers comprising chitosan and/or a chitosan derivative; (b) attaching the first and second layers to a third layer comprising a reinforcing material, such that the third layer is located between the first and second layers, wherein one or more of the layers further comprises a physiologically acceptable acid.

19. A method according to claim 18, comprising the steps of: (a) (i) mixing a chitosan and/or chitosan derivative with a non-aqueous solvent; and/or (ii) mixing a reinforcing material or carrier material with a solvent; (b) adding a physiologically acceptable acid to the or each mixture; (c) removing the solvent from the or each mixture to provide an acid coated component(s) being an acid coated chitosan, an acid coated chitosan derivative, a mixture of acid coated chitosan and chitosan derivative, an acid coated reinforcing material and/or an acid coated carrier material; (d) attaching first and second layers comprising chitosan and/or a chitosan derivative to a third layer located between the first and second layers comprising a reinforcing material, wherein one or more of the first and second layers comprises the acid coated chitosan, chitosan derivative and/or acid coated carrier material; and/or wherein the third layer comprises the acid coated reinforcing material.

20. A method according to claim 19, wherein the acid coated chitosan and/or chitosan derivative is attached to the reinforcing material by heat bonding or needle punching.

21. A method of absorbing fluid discharged from a physiological target site of a human or animal body, or of stemming a flow of a fluid discharged from a physiological target site of a human or animal body, comprising applying to the physiological target site a multilayer material according to claim 1.

22. Use of a multilayer material according to claim 1, in absorbing fluid discharged from a physiological target, or in stemming a flow of a fluid discharged from a physiological target site.

23. (canceled)

Description

[0153] Embodiments of the present invention will now be further described with reference to the following non-limiting examples and accompanying FIGURE in which:

[0154] FIG. 1: is a representation of a multilayer material of the present invention.

[0155] Referring to FIG. 1, there is shown a multilayer material (1) comprising first and second layers (2, 3) and a third layer (4). The first and second layers (2, 3) comprise chitosan and/or a chitosan derivative and the third layer (4) comprises a reinforcing material. Each of the layers (2), (3) and (4) are typically in fibrous form.

[0156] The multilayer material (1) further comprises a physiologically acceptable acid. Typically, the physiologically acceptable acid is coated onto the chitosan or chitosan derivative fibres forming the first and second layers (2, 3). Alternatively, it can be coated onto the fibres making up the reinforcing material to form the third layer (4). Alternatively still, the multilayer material (1) can further comprise a carrier material having the physiologically acceptable acid absorbed therein, or coated thereon. The carrier material may also be in the form of fibres. The carrier material, when present, is mixed with the chitosan and/or chitosan derivative in the first and/or second layers (2, 3), or segregated in separate portions in the first and/or second layers (2, 3).

[0157] In use, the multilayer material (1) can be rapidly applied to a wound site by removing any packaging and bringing either layer (2) or (3) into direct contact with the wound exudate. Beneficially, time can be saved as there is no need to analyse which surface of the multilayer material is the wound contacting surface, i.e. the surface that initially comes into direct contact with the wound exudate, since both layers (2, 3) are suitable.

[0158] Once applied, the physiologically acceptable acid dissolves in the wound exudate and contacts the chitosan. The dissolved acid reacts with the chitosan and/or chitosan derivative to form the corresponding salt of chitosan or chitosan derivative. The resultant salt gels upon contact with wound exudate, effectively encapsulating the fluid.

[0159] Furthermore, the reinforcing layer (4) typically comprises a superabsorbent material capable of absorbing wound exudate. Advantageously, this speeds up the time it takes to stem the bleeding from the wound.

EXAMPLES

Example 1

[0160] First and second layers, each being a 50 gsm layer of chitosan and Tencel, non-woven, and coated with lactic acid (Blend of chitosan:Tencel 55:45) between which lies a third layer of polyacrylate superabsorbent fibre (260 gsm), being a 50:50 blend of polyacrylate fibres and viscose fibres.

[0161] The layers were needle punched together.

Example 2

[0162] First and second layers, each being a 135 gsm layer of chitosan and Tencel, non-woven, and coated with lactic acid (Blend of chitosan:Tencel 55:45) between which lies a third layer of polyacrylate superabsorbent fibre (260 gsm), being a 50:50 blend of polyacrylate fibres and viscose fibres.

[0163] The layers were needle punched together.

Example 3

[0164] First and second layers, each being a 50 gsm layer of chitosan, non-woven, coated with lactic acid, between which lies a third layer of polyacrylate superabsorbent fibre (260 gsm), being a 50:50 blend of polyacrylate fibres and viscose fibres.

[0165] The layers were needle punched together.

Example 4

[0166] First and second layers, each being a 135 gsm layer of chitosan, non-woven, coated with lactic acid, between which lies a third layer of polyacrylate superabsorbent fibre (260 gsm), being a 50:50 blend of polyacrylate fibres and viscose fibres.

[0167] The layers were needle punched together.

Example 5

[0168] First and second layers, each being a 135 gsm layer of chitosan, non-woven, coated with lactic acid, between which lies a third layer of polyacrylate superabsorbent fibre (120 gsm), being a 50:50 blend of polyacrylate fibres and viscose fibres.

[0169] The layers were needle punched together.

Example 6

[0170] First and second layers, each being a 135 gsm layer of chitosan, non-woven, coated with lactic acid, between which lies a dry laid viscose polyamide layer (37 gsm).

[0171] The layers were needle punched together.

Example 7

[0172] First and second layers, each being a 135 gsm layer of chitosan, non-woven, coated with lactic acid, between which lies a dry laid viscose polyamide layer (37 gsm).

[0173] The layers are heat bonded together using a polycalprolactone adhesive.

Example 8

[0174] First and second layers, each being a 70 gsm layer of chitosan, non-woven, between which lies a 70 gsm layer of viscose, non-woven, coated with lactic acid.

[0175] The layers were needle punched together.

[0176] Example 1 Dressing:

TABLE-US-00001 TABLE 1 Absorbance and fluid retention data of the dressing of Example 1 Weight Absorbance Absorbance Retention (gsm) (g/g) (g/100 cm2) (%) Trilayer Mean 441.3 10.6 46.5 92.5 Std. dev 53.3 0.5 3.5 1.0

[0177] The results displayed in Table 1 show that the trilayer dressing of Example 1 was capable of achieving high absorbance and a high fluid retention of 92.5%.

[0178] The absorbency and tensile strength of the dressings of Examples 1-8 were tested with comparative examples of single layer dressings. The results are shown in Table 2.

[0179] For tensile strength, the results for Examples 1-7 show a value of >50 as the strength of the dressing was too high for load cell when dry (>50N). The wet strength was measured as >15N/25 cm.

TABLE-US-00002 TABLE 2 Absorbance and tensile strength data for test dressings Absor- Absorption Dry Wet bency under Tensile Tensile (g/100 compression (N/25 (N/25 Dressing example cm2) (g/100 cm2) mm) mm) Example 1 46.5 32.5 >50* 17.2 Example 3 44.5 28.6 >50* 16.3 Example 4 56.8 41.2 >50* 20.1 Example 5 48.3 36.4 >50* 16.9 Example 6 25.6 15.2 >50* 27.6 Example 7 20.1 12.4 >50* 28.3 Example 8 23.5 16.1 18.80 5.67 Alginate dressing single 21.28 13.52 12.40 9.88 layer Alginate dressing single 17.39 10.28 0.21 0.52 layer Carboxymethylcellulose 19.68 15.96 10.59 0.60 dressing single layer Carboxymethycellulose 27.93 18.8 37.19 15.69 dressing single layer with re-inforced stitch bonding Gelling fibre cellulose 23.75 18.08 13.63 1.23 dressing single layer Chitosan gelling fibre 28.59 16.12 23.69 2.16 dressing single layer *Reading greater than load cell capacity of tensiometer

[0180] The test methods are as follows:

[0181] Absorbency:

[0182] A 5 cm5 cm area of dressing was prepared and weighed. The test article was then immersed in saline solution (de-ionised water with 0.9% sodium chloride) for a period of 30 minutes. Following immersion, the test article was removed and excess fluid was allowed to drain. The dressing was re-weighed and the weight of fluid absorbed per weight and area of test article was determined.

[0183] Absorbency Under Compression:

[0184] A 5 cm5 cm area of dressing was prepared and weighed. The test article was applied to a test rig whereby a weight mimicking 40 mmHg pressure was applied on top. Saline solution (de-ionised water with 0.9% sodium chloride) was introduced to the test article and allowed to stand for a period of 30 minutes. Following absorbency, the test article is removed and excess fluid was allowed to drain. The dressing was re-weighed and the weight of fluid absorbed per weight and area of test article was determined.

[0185] Dry Tensile:

[0186] The test article was prepared to a width of 25 mm and positioned within a tensiometer. The force to break the test article was recorded.

[0187] Wet Tensile:

[0188] The test article was prepared to a width of 25 mm. 2 g of fluid (saline solution of de-ionised water with 0.9% sodium chloride) was applied to the central portion of the test article, allowing it to absorb for a period of 30 minutes. The test article was then positioned within a tensiometer. The force to break the test article was recorded.

[0189] The results displayed in Table 2 show that the wet tensile strength of the dressings of the present invention is increased at least compared to the Chitosan gelling fibre single layer. Further, for Examples 1-5 where the reinforcing layer comprises a polyacrylate superabsorbent fibre, the absorbency potential is significantly increased over all of the comparative dressings.

[0190] 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.