HK1101341B - Dressing for a wound - Google Patents

Description

Wound dressing

The present invention relates to a wound dressing.

It is generally believed that a moist environment promotes wound healing. While preventing the formation of scabs with little scarring. A moist environment may be created by the medium that assists in wound healing. For this purpose, absorbent materials are often impregnated with such media for application to the wound.

DE 29721345U 1 discloses a wound plaster in which a liquid chamber is provided between the adhesive film and the wound nonwoven. The liquid chamber is arranged such that the liquid contained therein can penetrate the wound nonwoven.

DE 19631421 a1 discloses an antibacterial wound dressing. The wound dressing is composed of a hydrophobic bacterial adsorption material containing an antibacterial active compound that is not released to the wound. With the aid of the hydrophobic material and in combination with the antimicrobially active compound, bacteria from the wound fluid are absorbed onto the wound dressing and are killed there. By removing the wound dressing, bacteria are also removed. It no longer interferes with the wound healing process.

DE 19727032 a1 discloses a plaster in which the application area has a first application area and a second application area arranged outside the first application area. The first pasting region has a smaller adhesive force than the second pasting region.

DE 19860759C 2 discloses a plaster with which the skin surface can be covered, the interior of which is filled. The patch consists of an elastic surface having an adhesive surface adjacent to one side of the skin with an annular pharmaceutically active carrier of an absorbent material disposed therebetween. The carrier contains a disinfectant for disinfecting the injection area surrounded by the carrier. Above the infusion area there is an elastic surface with openings and a protective film covering the adhesive surface and the pharmaceutically active carrier and which has to be removed before use.

DE 69718035T 2 discloses adhesive dressings with an adhesive composition in the form of a layer containing at least a part of an adjustable reinforcement. The adhesive composition and the reinforcing member are selected such that the adhesive dressing is breathable.

EP 1005301B 1 discloses a wound dressing for attachment to the skin having a first region opposite a substrate for contact with the wound and a second region containing an antimicrobially active compound surrounding the first region to prevent bacterial ingress from the external environment.

WO 02/056927 a2 discloses a multilayered dressing. Comprising an absorbent layer, a gas permeable, liquid impermeable outer layer, and a chamber in the absorbent layer for release of a liquid treatment medium. The dressing also contains a perforated layer that forms a covering over the wound. The outer layer may have an adhesive layer to enable the dressing to be secured around a wound. With this dressing, the wound can be kept closed and moist.

The invention aims to provide a wound dressing which can enable a wound to be better healed. In addition, a method for preparing the same will be disclosed.

The invention achieves the object of the invention by the following technical solution.

A wound dressing is provided according to the invention comprising a first layer formed from an absorbent substrate and an antimicrobial active which is chemically or physically associated with a surface of the substrate. The surface of the substrate, including the surface of the substance, is coated with a hydrophilic polymer. The matrix comprises fibers and can be composed of a nonwoven fabric, a gauze, a foam material, or another soft absorbent material. An advantage of the foamed material is that it can hold the material detached from the wound and thus can be kept away from the wound so that it does not interfere with the healing process. The matrix may comprise or be formed from at least one fiber. The surface of the substrate to which the substance is bound may thus be the surface of the fibre. The substance is preferably bound to the surface of the fibres or the matrix so that it is not or hardly lost from the matrix when used as desired.

The matrix or fibre can be prepared in which the substance is present in association with the surface of the matrix or fibre, for example by treating a polymer to form a matrix or fibre with the substance. In the resulting matrix or fiber, some of the substance is present at the surface of the fiber or matrix. However, a greater part usually enters the interior of the polymer-treated matrix or fiber so that it does not come into contact with liquids from the outside. It is therefore preferred that the substance is fully bound to the surface of the matrix or fibres. Therefore, it is not necessary to use an unnecessary amount of the substance in the preparation, and it is eventually difficult to obtain it.

A prerequisite for good wound treatment is that undesirable bacteria do not multiply in the matrix and in the liquid surrounding the matrix. For this purpose, the wound dressing contains an antibacterial active substance. If tested as described in DE 19758598A 1, which significantly delays or completely inhibits the propagation of microorganisms, the substances have an antibacterial activity. The antimicrobially active substance may also be a substance which, by conversion, produces an antimicrobially active compound in the environment in which the wound dressing is used as required. For example, if the antimicrobially active compound is a metal ion or an ionic complex containing a metal ion, the metal, alloys thereof, and other materials capable of releasing the metal ion or ionic complex containing a metal ion in the wound area will also have antimicrobial activity. The metal ions may be cations of silver, copper or zinc. Alternatively, the antimicrobially active substance may be metallic silver, copper or zinc or an alloy or other substance which can release the ions in the wound area.

The antimicrobial active may have antimicrobial activity against staphylococcus epidermidis or other microorganisms. According to the method disclosed in DE 19758598A 1, the antibacterial activity of the substances against other microorganisms was determined using the microorganisms studied in each case, but not the Staphylococcus. Particularly preferred substances are substances with antibacterial activity against one or more microorganisms selected from the group consisting of Bacillus, Clostridium, Enterobacter, Escherichia, Pseudomonas, Salmonella, Gluconobacter, Yersinia, Candida and Aspergillus.

It has been found that antibacterial actives, particularly those that are cytotoxic, can interfere with wound healing. The antibacterial active substance is cytotoxic if it has a cytotoxic action as described in DIN-ISO 10993-5. To prevent interference, the present invention provides that the substance should be bound to the surface of the matrix or matrix fibers. By combination, the above-mentioned antibacterial active substances can be prevented from reaching amounts at the wound site that interfere with wound healing. Furthermore, it is thereby possible to prevent the loss of the antimicrobial active substance from the wound dressing area due to absorption into the body, where it cannot have a long-lasting antimicrobial activity. Furthermore, absorption of the substance or causing an undesirable reaction in the body, such as allergy, can thereby be prevented.

With the wound dressing of the present invention, it is possible to prevent, for example, bacteria generated at the wound site from spreading at the wound site to cause wound infection or wound reinfection. By preventing the proliferation of bacteria for a long period of time, the wound dressing can be placed over the wound until the wound heals. Therefore, mechanical stress caused by peeling the wound dressing can be avoided, and a resting of the wound favorable for wound healing can be ensured. The main advantages of the wound dressing of the present invention are that it is practically sterile and that the wound healing process is not disturbed by antibacterial active substances.

The coating of the polymer needs to be thin and the polymer is chosen so that the action of the substance is not impeded. For example, the polymer may be a polymer formed by plasma polymerization of hexamethyldisiloxane. The coating enhances the bonding of the substance to the fiber or matrix. Clusters of particles of silver, for example plated by evaporation or deposition, are protected from mechanical wear. Wettability of the fibers or matrix is preferred due to the hydrophilic nature of the layer. A more uniform distribution of the liquid over the substrate can thereby be achieved. Furthermore, by improving the contact of the fibers or matrix with the liquid, a better action of the antibacterial active substance can be exerted. Furthermore, adhesion of gram-positive and/or gram-negative bacteria to the fibres or the substrate can be reduced by means of the hydrophilic polymer, in particular obtained by plasma polymerization. Furthermore, the hydrophilic layer improves the sliding behavior of the substrate or individual fibers of the substrate in a humid environment due to the formation of a liquid film directly on the surface of the coated substrate or fibers. Thus, if the matrix is present over the wound, it slides easily over the wound in the event of displacement, in the process of which only a small mechanical stress is applied to the wound. Thus, the wearing comfort of the wound dressing is significantly increased with a reduced liquid cushion between the substrate and the wound. Furthermore, the liquid film on the coated film or substrate also prevents the wound from forming new tissue growth into the substrate.

The wound dressing preferably has a second layer formed of a gas permeable, liquid impermeable film attached to a substrate and has a self-adhesive first region. The substrate is attached to the membrane in the second region. By way of example, the manner in which the substrate is attached to the membrane is such that: which is adhered to or bonded with the membrane. The first self-adhesive region is a region of the film which surrounds, preferably at a distance from, the second region by which the wound dressing may be applied to the skin of a human or animal. The result of the attachment is a liquid-tight interior space which is filled with a liquid-containing matrix. The interior space enables liquid wound care.

The theoretical basis for an embodiment of the invention is that in normal moist wound treatment the adsorbent material begins to dry at a stage prior to wound healing, and as a result the wound draws moisture. Thus, the wound healing process is adversely affected.

Furthermore, embodiments of the present invention are based on the recognition that: wound healing may not only improve wound healing by moisturizing the wound, but also provide more fluid to form a fluid cushion on the wound. As a result, healing of the wound is improved and the tendency to scar is reduced. Such wound care is termed herein as liquid wound care. Use of the wound dressing of the invention is firstly achieved by placing the wound dressing dry on the wound to be treated and applying it to the skin surrounding the wound by means of the self-adhesive first region so that the wound region can thereby be sealed against liquids. The membrane can then be pierced by means of a cannula so that the liquid is injected into the interior region of the underside. After removal of the cannula, the opening created in the membrane may be sealed by an adhesive membrane. It is advantageous to inject the liquid multiple times, for example once a day. Finally, it can be ensured that the wound is permanently preserved under the liquid pad until healing and until the wound dressing is removed.

The self-adhesive first region preferably provides an adhesive which has a high affinity for skin and is insoluble in aqueous liquids. Such adhesives are known in the prior art, especially in the field of plasters. Furthermore, the adhesive should be able to withstand the increased liquid pressure in the inner space without detaching from the skin. The increased liquid pressure is already generated when the liquid is injected and the membrane exerts a tension. For example, increased fluid pressure may also be caused by mechanical stress on the wound dressing induced by the patient, such as movement of the body part in which the wound is located.

Due to the fact that the substrate is connected to the membrane, the substrate can be lifted away from the wound by means of the liquid pad. Thus, the wound is not in direct contact with the substrate and the antibacterial active. Unwanted proliferation of newly formed tissue in the wound into the stroma is also avoided by lifting the stroma away from the wound. Thus, as disclosed in WO 02/056927 a2, it is not necessary that the perforated layer form a covering over the wound and separate the wound from the matrix. As with known wound dressings, the matrix herein serves as a carrier for the substance and not for the purpose of keeping the wound moist. By positioning the self-adhesive first region at a distance from the second region, the matrix is attached to the second region by the membrane, which is helpful for the matrix to be lifted from the wound.

Wound disinfection is achieved by appropriate selection of the liquid. For example, the pH of the liquid is low enough to ultimately inhibit bacterial growth. Furthermore, liquids with low pH have an astringent effect on the wound, thereby aiding the healing process. Furthermore, the solution may contain elements and/or nutrients that stimulate cell growth.

The substance is preferably inorganic, in particular a metal or a metal compound. Such antibacterial actives are generally inexpensive, readily available, and easy to process. A metallic compound is herein understood to mean a mixture or alloy of at least two metals. The metal ion or the complex containing the metal ion may be formed of a metal or a metal compound as an active material and released. Preferably, the oligodynamic activity, such as a very small amount of an antimicrobially active metal or a oligodynamic active antimicrobial metal compound.

In a preferred embodiment, the substance is selected from the group consisting of silver, copper and zinc, their ions and their metal complexes or mixtures or alloys comprising at least one of the foregoing components. In addition to the metals mentioned above, the alloy contains, in particular, gold and/or platinum. These substances are resistant to a wide variety of different bacteria and interfere in many ways with their metabolism. Therefore, the use of these substances causes less resistance in bacteria than the use of special-acting organic antibacterial substances, such as antibiotics. These substances are preferably silver, silver cations or silver complexes or complexes releasing silver cations or silver alloys or alloys releasing silver cations. In particular, silver metal is easy to process and is available in relatively large quantities at relatively low cost, so that, by analogy, the wound dressing of the invention can also be produced relatively inexpensively.

The metal or metal compound can be applied in clusters to the surface of the fiber or substrate, in particular by evaporation or deposition by a sputtering process or chemical vapor deposition. In the case of evaporation or deposition, the metal or metal compound is evaporated by heating in a vacuum and the metal vapor is subsequently deposited on the fiber or substrate. The metal or the metal compound is present in clusters on the fiber or the substrate by evaporation or deposition plating. The clusters have particularly good antimicrobial properties.

The substance present in the wound dressing according to the invention is suitably in particulate form, preferably with particles or granules having an average diameter of from 5 to 100 nm. The substance may be present as individual particles or as interconnected particles. Fine particles of these antibacterial active substances can be easily prepared, especially for inorganic substances, especially for silver in the present invention, but also for copper and zinc, and also mixtures, complexes and alloys of the three metals. Due to the small average particle size, the specific surface area of the material is so large that it is easily detached from the substrate, especially by diffusion. Furthermore, due to the large specific surface area, the particulate active compound sometimes produces chemical inertness in the wound environment, but usually only a part of the surface is involved, so that the substance can be released from the matrix in adverse circumstances. It has proven advantageous for the mean particle diameter of the substance to be in the range from 5 to 50 nm, preferably from 5 to 20 nm. If the substance is silver or a silver alloy, the particle size distribution is also considered to be nanoscale silver or a nanoscale silver alloy.

The substance is present in a layer thickness of at least 1 nm and preferably not more than 1 mm. If particulate matter is used, the layer is at least as thick as the active compound particles. Preferably the average layer thickness is at least 5 nm to 100 nm, particularly preferably the layer thickness is 10 nm to 50 nm, particularly if the substance is silver, copper and/or zinc or ions, metal complexes or mixtures or alloys of these elements. It has been shown that even a small thickness of the layer of the antibacterial substance, in particular comprising nano-sized silver, is sufficient for the purpose of achieving an antibacterial but non-toxic cell effect.

The substance is preferably present in an amount such that it has an antimicrobial effect in the event that the matrix is saturated with liquid in the matrix, especially throughout the matrix. The above amounts can be determined by simple routine tests. If the substance is metallic silver, sufficient antimicrobial action can be obtained by providing a silver content in the matrix of between 1 microgram and 200 microgram per square centimeter of the maximum area covered by the matrix. Higher silver levels are undesirable because the amount of silver ion released is sufficient to adversely affect wound healing.

Preferably, the polymer is a polymer that reduces the adhesion of bacteria, preferably gram negative bacteria or staphylococci, especially staphylococci, to the fibre or matrix. In addition to the substance, the method also reduces colonization of the substrate by bacteria.

Preferably, the fibers or substrate are surface coated with a polymer by plasma polymerization. Thus, very thin embodiments of the coating are possible, which hardly adversely affect the action of the substance. The properties of the polymer can be varied during the plasma polymerization by means of the selection of parameters. The person skilled in the art will be able to determine suitable starting materials and suitable production parameters for the polymer layer by routine experimentation. For example, the coating of the substrate with the antibacterial substance and plasma polymerization may be carried out as follows:

in a first step, clusters of nano-sized silver particles are coated on a substrate consisting of a non-woven fabric. For this purpose, metallic silver is evaporated at an operating pressure of about 10 mbar, for example under an argon protective atmosphere. In this process, silver is deposited on the substrate as individual particles or as interconnected particles. The silver particles have an average particle size of about 10 nm to about 20 nm. The silver is plated at a thickness of about 20 nm. In a second step, a plasma polymer layer containing Hexamethyldisiloxane (HMDSO) is applied as a monomer or precursor. The plasma polymerization was carried out at a working pressure of 0.07 mbar using 95% oxygen and 5% HMDSO as working gas. After plasma polymerization was thus carried out for 45 seconds, the silver plating was up to 45 nm in thickness and had a strongly hydrophilic plasma polymer layer. The coating surface energy here is 105 milli-newtons per meter.

The application of the polymer to the fibers occurs before or after the matrix is prepared from the fibers. If this occurs later, the entire substrate, e.g.the nonwoven or woven fabric, is subjected to a coating process, e.g.plasma polymerization. It is particularly preferred if the polymer is oxidized after the plasma polymerization. Thereby, a highly hydrophilic surface can be created.

In a preferred embodiment, the polymer is formed from monomers of acrylic acid, or from monomers based on siloxanes, in particular hexamethyldisiloxane. Such polymers may combine antibacterial adhesion with excellent hydrophilicity. It also allows the polymer coated material, such as metallic silver, to have a good effect on the substrate.

The polymer is preferably present in a layer having an average thickness of from 5 nm to 500 nm. However, especially for plasma polymerized polymers, the thickness is preferably from 5 nm to 200 nm, preferably from 10 nm to 100 nm. At these layer thicknesses, the use of polymer layers prepared by plasma polymerization, in particular, can lead to coatings which are distinguished by outstanding antibacterial properties and by no cytotoxicity. At the same time, these coatings are so thin that they are barely perceptible to the naked eye or may even be transparent.

Preferably, the amount of the substance therein is calculated such that the amount of active compound produced and/or released by the substance does not have a cytotoxic effect on the wound under the application conditions. Such amounts can be determined by simple routine experimentation. The active compound may be, for example, a metal ion or a complex of such metal ions. If the substance is silver, a suitable amount of silver in the matrix is 1 microgram to 200 microgram, preferably 5 microgram to 35 microgram, in particular 5 microgram to 15 microgram per square centimeter of the maximum area covered by the matrix. It has not previously been recognized that the commonly used silver-containing wound dressings release silver ions in a total amount that is cytotoxic to the wound. Thus, wound healing is disturbed.

Substances which aid wound healing, especially growth factors, are preferably bound to the matrix. Such a substance may be, for example, Epidermal Growth Factor (EGF), platelet growth factor (PDGF), Vascular Endothelial Growth Factor (VEGF) or Keratinocyte Growth Factor (KGF). Preferably, the matrix is completely soaked or impregnated with a liquid that facilitates wound healing, in particular an acidic liquid or a liquid containing nutrients that facilitate wound healing.

In a particularly preferred embodiment, the film is at least partially transparent. Thereby, the liquid level below the membrane can be observed, so that a new liquid can be refilled as soon as a decrease of the liquid content in the inner space is observed.

In a further particularly preferred embodiment of the invention, the entire wound dressing, including the substrate and the film, is transparent, in particular to ultraviolet, infrared or near-infrared light.

This can be achieved by selecting appropriate materials. Thus, the wound may be exposed to light treatment without removing the wound dressing. Phototherapy can significantly accelerate wound healing.

Preferably the wound dressing contains an indicator. The indicator may be a pigment which indicates a certain condition of the wound dressing or wound. For example, in connection with this, a pH indicator is capable of changing its color depending on the pH. The change in color is visible through the film, which is transparent at least at ordinary locations. The indicator can also be formed by most substances that interact to indicate a certain state. The indicator may also be a sensor. The sensor may be, for example, a conductive polymer that changes its conductivity depending on the condition of the wound or wound dressing. The sensor may also be a biosensor. A biosensor is understood to mean a measuring probe in which a biomolecule is coupled to a signal transducer, for example a potentiometer sensor. The signal converter converts a signal generated by binding a specific substance to a biomolecule into an electric signal. The sensor may be part of the field of sensors or biosensors comprising a number of sensors. With the aid of different sensors, a number of parameters characterizing the wound or the wound dressing can be determined simultaneously.

The indicator may also be an indicator of the amount of liquid in the matrix. Thus, drying of the matrix can be detected better and earlier. The indicator may also be an indicator of the degree or type of microbial contamination of the substrate or wound. This can be achieved, for example, by immunological indicators. In this case, for example, the microorganism or a part of the microorganism is bound by the antibody and thereby a color reaction is initiated. The indicator may also be an indicator of inflammatory wound conditions. Such indicators are likewise immunological indicators. In this case, the inflammatory factor specifically binds to the antibody and thereby initiates a color reaction.

Furthermore, the present invention relates to a method of preparing a wound dressing according to the invention, having the steps of:

-obtaining an absorbent matrix,

obtaining a gas-permeable but liquid-impermeable membrane,

-applying a first self-adhesive area (16) on the film and

attaching an absorbent matrix to the membrane in the second region of the membrane,

-the first region of the membrane surrounding the second region of the membrane,

on the substrate or the fibers forming the substrate, the antimicrobial active is first deposited by evaporation or deposition, sputtering process or chemical vapor deposition, and then the polymer is deposited by plasma polymerization.

The substrate may be a nonwoven, gauze, foam, or other soft absorbent material. The substance and the polymer may be deposited on the resulting substrate. The fibers are not necessarily the only fibers forming the matrix. The fibers forming the matrix may be fibers incorporated into the matrix during or after the matrix is prepared. By evaporation or deposition, sputtering processes or chemical vapor deposition in combination with plasma polymerization, coatings can be obtained in which the substance is particularly thin and simultaneously has a high antimicrobial activity, and coatings in which the polymer with particular properties is particularly thin for fibers or substrates. Only small amounts of substances or polymers are required. The substance is protected by the polymer, in particular against mechanical abrasion.

An embodiment of the invention is explained in more detail below with the aid of the accompanying drawings:

figure 1 shows a schematic diagram illustrating a side view of a wound dressing of the invention,

figure 2 shows a schematic diagram representing a top view of a wound dressing of the invention,

FIG. 3 shows a series of graphs showing the time course of bacterial growth as measured in terms of Optical Density (OD) when contacted with conventional substrates as well as wound dressing substrates of the invention.

Figures 1 and 2 show a wound dressing 10 of the invention having an absorbent substrate 12, a gas permeable but liquid impermeable membrane 14 and a first self-adhesive region 16. The first region 16 is herein a region of the film in which the adhesive is coated. Here a first area 16 surrounds a second area 17 of the membrane in contact with the substrate. When it is desired to use wound dressing 10, matrix 12 is placed over wound 18 and self-adhesive first region 16 is circumferentially affixed to the skin surrounding wound 18. Thereafter, the liquid is injected through the membrane 14 into the inner region formed by the bonding together. The holes formed upon injection into the membrane 14 are sealed by an adhesive membrane.

In an application study, the wound dressings of the invention used in the first group of patients had the fibers of the matrix coated with silver and a hydrophilic polymer obtained by plasma polymerization of hexamethyldisiloxane. The wound dressing in this case is used for at least 4 days or more for postoperative fluid wound care of funnel chest clinical presentation. A second group of patients used conventional wound care for comparison. No infection occurred in the first group of patients, whereas the second group of patients occasionally presented with infection. Moreover, due to the hydrophilic coating, the wearing comfort of the wound dressing of the invention is significantly higher than that of wound dressings used for conventional care. Liquid wound care using the wound dressing of the present invention may heal faster with less tendency to form scars. The matrix of the wound dressing for wound care still had antimicrobial activity on the wound after 4 days as shown in the experiment shown in figure 3.

The results shown in FIG. 3 have been determined according to the method disclosed in DE 19758598A 1. This method is also disclosed in Bechert, Thorsten et al, Nature Medicine (2000), Vol.6, No. 8, p.1053-1056. The disclosures of both of these documents are included herein. The substrates tested were used as described in this test.

In FIG. 3, each region shows an x-y plot with time labeled on the x-axis and optical density labeled on the y-axis. The test results shown in columns 1, 2, 4, 5, 11 and 12 of FIG. 3 have been determined in parallel tests of batches of A-H, using the following substrates for the corresponding rows A-H:

column 1, rows A-H: the substrate is not coated with a solvent,

column 2, rows A-H: a substrate coated with silver and a polymer obtained by plasma polymerization of hexamethyldisiloxane,

column 4, rows A-H: substrates coated with silver and a polymer obtained by plasma polymerisation of hexamethyldisiloxane, from the first wound dressing used for 4 days in the above application study,

column 5, rows A-H: substrates coated with silver and a polymer obtained by plasma polymerisation of hexamethyldisiloxane, from the second wound dressing used for 4 days in the above application study,

column 11, rows A-H: sterility comparison

Column 12, row a: front contrast

Column 12, row B: contrast on the reverse side

Column 12, row E, F: blank value

In the case of the sterility comparison, only medium was used in each case without addition of staphylococci to show that bacterial propagation was not caused by the medium. In the case of a positive comparison, a metal-silver-containing polymer was used. The values indicate that the bacteria used are sensitive to and can kill silver. In the case of the reverse comparison, the same polymer was used, however without silver. Blank values are values determined in hollow microtiter plates, which are subtracted out in all calculations of the measurements.

The test results show that the wound dressing of the present invention, in which the substrate is coated with silver and a polymer obtained by plasma polymerization of hexamethyldisiloxane, has high antibacterial and bactericidal effects. This effect was still present on the wound after 4 days.

Claims (25)

1. Wound dressing (10) comprising a first layer of an absorbent substrate (12) and an antimicrobial active which is in chemical or physical connection with one surface of the substrate (12) comprising a substance coated with a hydrophilic polymer, the wound dressing (10) comprising a second layer of a gas permeable, liquid impermeable membrane (14) attached to the substrate (12) and having a self-adhesive first region (16), the substrate (12) and the membrane (14) being attached to the second region (17) and the first region being a region of the membrane (14), the first region (16) surrounding the second region (17), through which the wound dressing (10) can be attached to the skin of a human or animal, the attachment resulting in a liquid impermeable interior space, the interior space being filled with a liquid, the antimicrobial active substance is a metal or a metal compound.

2. The wound dressing (10) of claim 1, the substrate (12) having or being formed from at least one fibre, and the antimicrobially active substance being bound to a surface of the substrate (12), the surface of the substrate (12) being the surface of the fibre.

3. A wound dressing (10) according to claim 2 in which the antibacterial active is fully bound to the surface of the fibre.

4. A wound dressing (10) according to claim 1 or 2, the antimicrobially active substance being selected from the group consisting of silver, copper and zinc, their ions and their metal complexes, or mixtures or alloys comprising at least one of these components.

5. A wound dressing (10) according to claim 1 in which the metal or metal compound is capable of being applied in clusters to the surface of the substrate.

6. A wound dressing (10) according to claim 1 or 2, the mean particle size of the antimicrobially active substance is between 5 nm and 100 nm.

7. A wound dressing (10) according to claim 1 or 2, in which the layer of antimicrobially active substance is present in an average thickness of from 5 nm to 100 nm.

8. A wound dressing (10) according to claim 1 or claim 2 in which the antibacterial active substance is present in an amount such that the liquid in the substrate (12) is antibacterial active in the event that it is fully impregnated into the substrate (12).

9. A wound dressing (10) according to claim 1 which is a polymer that reduces bacterial adhesion to the fibre or substrate.

10. A wound dressing (10) according to claim 2, the fibres or surface of the substrate (12) being those coated with the polymer by plasma polymerisation.

11. A wound dressing (10) according to claim 10 which is a polymer that has been oxidised after plasma polymerisation.

12. A wound dressing (10) according to claim 1, the polymer being formed from acrylic monomers, or from silicone-based monomers.

13. A wound dressing (10) according to claim 1 in which the average thickness of the layer in which the polymer is present is from 5 nm to 500 nm.

14. A wound dressing (10) according to claim 1 or claim 2 in which the antibacterial active substance is present in an amount such that, in use, the active compound formed and/or released by the antibacterial active substance is in an amount that does not cause cytotoxic effects on the wound.

15. A wound dressing (10) according to claim 1 or claim 2 in which the antibacterial active substance which assists in wound healing is bound to the substrate (12).

16. A wound dressing (10) according to claim 1 or claim 2 in which the matrix (12) is fully soaked or filled with a liquid which assists in wound healing.

17. A wound dressing (10) according to claim 1 in which the film (14) is transparent, at least in the usual position.

18. A wound dressing (10) according to claim 1 or 2 which is transparent to light.

19. A wound dressing (10) according to claim 1 or claim 2 which includes an indicator.

20. A wound dressing (10) according to claim 19, the indicator being a sensor.

21. A wound dressing (10) according to claim 20, the sensor being a conductive polymer which changes its conductivity depending on the condition of the wound or wound dressing.

22. A wound dressing (10) according to claim 19 which may also be an indicator of the liquid content of the matrix (12).

23. A wound dressing (10) according to claim 19, the indicator being an indicator of the extent and/or kind of microbial contamination of the substrate (12) or wound.

24. A wound dressing (10) according to claim 19, the indicator being one which is indicative of a wound inflammatory condition.

25. A method of making a wound dressing (10) as claimed in any preceding claim, having the steps of:

-obtaining an absorbent matrix (12),

-obtaining a gas-permeable but liquid-impermeable membrane (14),

-applying a first self-adhesive area (16) on the film (14) and

-attaching an absorbent matrix (12) to the membrane (14) in a second zone (17) of the membrane,

-a second area (17) of the membrane (14) is surrounded by the first area,

on the substrate (12) or the fibers forming the substrate (12), the antimicrobial active is first deposited by evaporation or deposition, a sputtering process or chemical vapor deposition, and then the polymer is deposited by plasma polymerization.