HK1068246B - Wound dressings and wound treatment compositions - Google Patents

Description

Wound dressing and wound treatment composition

Technical Field

The present invention relates, in a first aspect, to wound dressings and, more particularly, to wound dressings of the generic type comprising an absorbent or adsorbent composition, optionally together with one or more other compounds, usually in powder or granular form, contained in a sachet made of a moisture permeable material. Such wound dressings may contain one or more different absorbent or adsorbent compositions, the purpose of which is to absorb or absorb exudate from the wound to facilitate (and often accelerate) the healing process. The one or more additional compounds may also promote the healing process. The present invention is particularly, although not exclusively, concerned with wound dressings suitable for treating relatively large wounds and large areas of skin.

The invention also relates to a wound treatment composition which can be used in different forms, but is preferably used in a wound dressing, in particular a wound dressing according to the invention. In this regard, the present invention more particularly relates to the inventor's earlier south african patent No. 93/9117 and its european counterpart, namely european patent application publication No. EP-0601835, and the inventor's later international patent application publication no: compositions of the general type described in WO 00/09176. As noted above, such wound treatment compositions may be used to promote faster healing of the wound.

Background

In the past, wound dressings of the type described above have all had a sheet of woven or non-woven fibres forming the surface of the dressing which, in use, is in actual contact with the wound.

A disadvantage of this construction is that the fibrous material has a tendency to adhere significantly to the wound and this can have a serious detrimental effect when the dressing is to be removed. In fact, the patient suffers considerable pain when the dressing is removed and a great deal of the benefit gained by the healing process is lost. This is generally not improved by interposing a layer of scrim, or other fibrous material, usually a fibrous pad or the like, between the wound and the dressing, since the fibers of the scrim or pad then adhere to the wound. In addition, granulation tissue is destroyed during such removal of the dressing, and this often delays the healing process.

With respect to therapeutic compositions, in said earlier patent applications, the inventors describe wound treatment compositions consisting of two basic ingredients, namely a preservative or antimicrobial agent and a desiccant, the term desiccant referring to a compound acting on an adsorptive rather than absorption basis. Preferred compositions comprise sodium chloride or sucrose as the antimicrobial agent and silica gel as the desiccant.

Although these compositions have a useful effect from a medical or even therapeutic point of view, they have, from another point of view, the disadvantage that sodium chloride or sucrose is to some extent dissolved in the adsorbed moisture. As a result, sodium chloride or sucrose can migrate through the moisture permeable membrane, which is typically part of the envelope containing the composition, and is believed to form a barrier between the composition and the wound itself. As a result, in the case of sodium chloride, the patient suffers considerable pain due to the sodium chloride entering the wound. In the case of the use of both sodium chloride and sucrose, the composition may also adhere to the wound to some extent, thereby creating difficulty in removing the dressing, which is another possible factor of pain for the patient.

Collagen is widely used directly as a wound treatment composition. Many different methods and carriers have been proposed and used for applying them to wounds, for example directly to wounds in the form of: in the form of granules; in the form of a suspension; in the form of a gel, optionally in combination with other active ingredients such as iodine; forming an exposed layer in a central portion of the adhesive dressing; and as an active ingredient in a spray for application to a wound.

Us patent 5,800,372 discloses a field dressing in which collagen is used to promote blood clotting in a freshly formed wound to stop bleeding and to allow the subsequent clotting to spread to the wound. Mixing collagen with superabsorbent polymers can absorb large amounts of liquids contained in blood.

It has now surprisingly been found that the advantageous effects of collagen can be exploited and for which the applicant believes it is a new and very effective way.

Disclosure of Invention

It is therefore an object of the present invention to provide a wound dressing which is more easily separable from the wound than prior art dressings as described above. It is a further object of the present invention to provide a wound treatment composition which reduces, at least to some extent, the disadvantages of the wound treatment compositions heretofore proposed by the present inventors.

According to one aspect of the present invention there is provided a wound dressing having an inner wall (5) for contact with a wound in use, the inner wall being perforated (7) to allow exudate or slough to pass therethrough, and a sheath remote from the outer wall of the wound, wherein a wound treatment composition is contained within the sheath, the wound treatment composition comprising at least one absorbent or adsorbent compound in the form of silica gel, the wound dressing being characterised in that the silica gel is mixed with collagen.

Other features of the invention are: the surface of the inner wall which in use is in contact with the wound is a substantially smooth continuous plastics surface, typically the exposed surface of the plastics inner wall of the outer casing; the inner wall of the sheath is a medical grade polypropylene or other suitable plastic film with, for example, perforations, the film having a thickness of from about 15 microns to about 180 microns; the outer wall of the sheath is a perforated plastic film, conveniently of polyethylene, preferably having a layer of superabsorbent material, for example of weight about 40 to about 180g/m, bonded to its side adjacent to the inner wall²The fluff pulp fabric of (1); the wound treatment composition is contained in one or more preformed permeable sachets, the one or more moisture permeable sachets being located in the outer sleeve.

The moisture permeable material of the sachet is preferably from about 15 to about 60g/m in weight²For example, materials used in the manufacture of tea bags, or alternatively, cellulosic materials.

The casing is preferably produced in the following manner: each casing is interconnected with a series of adjacent casings to form a continuous row of casings which are interconnected by regions of sheet material of the sheet material forming the inner and outer walls of the casing, the regions of sheet material being located around the casings and the regions being fused together, typically by heat fusion, at least along predetermined lines, to define the peripheral boundary of each casing. Preferably heat-welded along two separate parallel lines to define a region of sheet material between the sheaths themselves, a predetermined line of weakness being formed along said region between the two parallel weld lines, along which line of weakness one or some of the sheaths may be cut or torn off. Of course, it is not necessary to form the outer cover by welding two sheets of material, but it is equally possible to sew, glue or otherwise secure them together.

From a structural integrity point of view, additional sheets may be additionally added to facilitate thermal welding, for which a sheet of non-woven fibres may be interposed between the inner wall, which is a substantially continuous surface in contact with the wound, and the absorbent or adsorbent compound, and a similar layer may be provided on the outside of the outer wall, so that the two similar layers can be effectively bonded together by heating, and the inner wall can be attached to the composite structure, thereby ensuring structural integrity.

The wound treatment composition is preferably a wound treatment composition according to the second aspect of the invention as defined below. However, the first aspect of the invention extends to other wound dressing compositions, in particular to other absorbent and adsorbent materials. Such absorbent or/and adsorbent materials may then be, for example, finely divided porous ceramic materials sold as various wound dressings in the form of individual sachets of permeable fibrous sheet material.

According to a second aspect of the invention, there is provided a wound treatment composition comprising, in combination:

(a) a silicone gel for adsorbing moisture on or around a wound; and

(b) collagen protein.

The collagen may be any medically acceptable collagen, and conventional food grade gelatin has been found to have a useful effect. The ratio of the adsorbent material to collagen may vary widely, but it is presently determined by the applicant that in the case of gelatin and silica gel, the ratio is about 10 to 15% by weight gelatin to about 85 to 90% by weight silica gel.

The wound treatment composition may further compriseAn indicator that changes a visible physical property, particularly a color thereof, in the presence of moisture to indicate moisture saturation of the wound treatment composition, thereby indicating the necessity of changing the wound treatment composition. The indicator may be cobalt chloride (CoCl)₂) It is blue when it is in anhydrous form, but turns pink when it is in hydrated form. Typically the amount of cobalt chloride is about 0.5% by weight of the wound treatment composition. Conveniently, cobalt chloride may be chemically bonded to a portion of the silica gel to form SiOCoCl₂In the form of (1), and the remaining silica gel is still SiO₂In the form of (1). In this case, the cobalt-containing silica gel may comprise about 1% of the total silica gel.

The invention also provides a wound dressing comprising a quantity of a wound treatment composition as described above contained in a sheath or sachet as described above.

The pouch or sheath is typically substantially flat, but may be made in any shape, such as an elongated plug shape for insertion into a wound. When it is a plug or the like, the wound dressing may comprise a gripping formation, optionally in the form of a depending tab attached, for example, to one end of the plug and optionally integral with the pouch or sheath.

According to another aspect of the invention there is provided a wound treatment kit comprising a wound treatment composition according to the invention, typically in the form of one or more sachets or jackets containing same, and comprising separate holding means for holding the wound treatment composition in contact with a wound.

For a more complete understanding of the present invention, embodiments thereof will now be described and illustrated with reference to the accompanying drawings.

Drawings

FIG. 1 is a schematic perspective view of a preferred wound dressing of the invention, with the layers partially cut away to show its construction;

FIG. 2 is a schematic perspective view similar to FIG. 1 showing an alternative configuration for providing additional integrity to the composite dressing;

FIG. 3 is a schematic perspective view showing a single pouch containing a wound dressing composition and which may be used inside a casing of a wound dressing as shown in FIG. 1;

FIG. 4 is a schematic perspective view showing a packaged wound dressing of the type shown in FIG. 1; and

fig. 5 to 9 show a series of different forms, respectively, in which the wound dressing of the invention can be manufactured, packaged or shipped.

Detailed Description

Various preferred forms of wound dressings and preferred wound treatment compositions according to the present invention will now be described.

In this embodiment of the wound treatment composition, the composition comprises a dry mixture consisting of: silica gel (SiO)₂)615 parts by weight (about 88% by weight); 6 parts by weight (about 1% by weight) of moisture indicate silica gel, i.e. indicator of cobalt chloride attached to silica gel (SiOCoCl)₂) (ii) a And 79 parts by weight (about 11% by weight) of food-grade gelatin as collagen.

As shown in figures 1 and 3, the wound treatment composition (1) is prepackaged in a pouch (2) and heat sealed around the perimeter as shown by numeral (3) to enclose the solid particulate material (1) in a highly permeable sheet material pouch. The sheet material may be of the same type as the material normally used to produce tea bags and may in particular be a non-woven fibrous polypropylene material having a weight of from 15 to 60g/m²。

In various applications of the wound dressing composition of the invention, the above-described sachets may be applied directly to the wound, although in doing so, difficulties as described above in connection with prior art wound dressings are encountered. Accordingly, it is preferred to apply the wound dressing composition in the form of a wound dressing provided by the present invention.

For this purpose, the preformed sachets are sandwiched between sheets of material described below to form a jacket around the sachets (when more than one sachet is used in a jacket, a jacket is formed around the plurality of sachets).

In one embodiment of the invention, two sheets of material are formed into a sheath as shown in figure 1 and the sheets of material adjacent the edges (4) of the sheath are heat fused together to enclose a sachet of wound treatment composition. The two sheets are different from each other, the sheet forming the inner wall of the sheath (i.e. the surface in contact with the wound) being indicated by the numeral (5), and the sheet on the outer wall remote from the wound forming the composite wall indicated by the numeral (6).

The inner wall (5) consists of a smooth continuous plastic film, usually of medical grade polypropylene. Moisture is made permeable by forming a plurality of holes (7) in the inner wall (5). The thickness of the above-mentioned film may be 15 to 180 micrometers, preferably about 20 micrometers thick.

The outer wall (6) is formed from a composite sheet material having an outer layer (8), the outer layer (8) being a low density polypropylene with small holes (9) to enable the outer wall to be breathable to a sufficient degree. The inner layer (10) is made of absorbent cellulose fluff pulp with a binder in order to provide sufficient integrity. The inner layer may be 40 to 80g/m²。

In use, it has been found that the wound dressing produced by the above method is very effective and does not adhere to the wound when the polypropylene film is in contact with the wound. The perforations of the film are sufficient to allow exudate to pass through the impermeable film, the exudate being absorbed by the silica and the excess exudate being absorbed by the absorbent fluff pulp layer.

As shown in fig. 4, a wound dressing of the above described form may be packaged for sale with a protective sealed overwrap (11) and may be sterilized after packaging in known manner, for example by gamma irradiation.

To ensure the integrity of the envelope enclosing the sachet, due to the different types of materials from which the inner and outer layers are made, it is contemplated that 2 similar sheets (11) and (12) of highly permeable non-woven fibres may be added as required to enclose the wound treatment composition, as shown in figure 2. Typically these sheets may be fibrous polypropylene sheets. The additional sheet (11) may be located outside the outer wall (6) and a further sheet (12) located between the inner wall (5) and the sachet. The two similar plastic sheets are very effectively welded together, thereby ensuring that the wound treatment composition is effectively enclosed, and the inner wall (5) can be welded or otherwise attached to the resulting structure.

It may be convenient to manufacture large sheets of the wound composition of the invention by positioning the preformed sachets, conveniently on the composite sheet, preferably by "spot" welding, although adhesive bonding may be employed; the inner and outer sheets are then heat fused together along parallel lines (13) separated in figures 4-7, the parallel lines (13) being between the locations of the sachets. This leaves a narrow region (14) of the sheet between the parallel lines along which the sheet can be broken to give a wound dressing of suitable size.

It is also conceivable that the areas (14) between the parallel lines of heat-welded seams on the casing are suitably made as weak connections to break by tearing, thereby avoiding the necessity of scissors. However, it is not preferred to perforate these regions in order to separate adjacent sheaths and sachets, in order to maintain the waterproof properties of the wound dressing as a whole and to prevent exudate from leaking to the outer surface.

It will therefore be appreciated that the wound dressing of the present invention may be provided in a number of different configurations, some examples of which will now be described with reference to figures 5 to 9.

Figure 5 shows a wound dressing for treating a small wound, the wound dressing consisting of a sheath enclosing a single sachet of wound dressing composition (as described above).

The wound dressing shown in figure 6 consists of two sheaths which are held connected by a region (14) of sheet material.

FIG. 7 shows a larger dressing consisting of four sheaths and enclosed pouches; while figure 8 shows a larger dressing consisting of twenty interconnected sheaths and sachets, the dressing is particularly useful for treating large areas of damage to the skin, such as burns.

Figure 9 shows another form in which a wound dressing of the invention is provided in roll form (15) which can be cut or ruptured along the region between the adjacent sheath and sachet to form a wound dressing of any size required for any particular application.

It will be appreciated that many variations may be made to the embodiments of the invention described above without departing from their scope.

In particular, as mentioned above, the sachet may be used directly in a number of different ways without it being enclosed in a jacket as described above. In particular, a plurality of sachets of this type as shown in figure 3 may be attached to the support layer, for example. The support layer may also be made of a non-woven material and may have a moisture impermeable layer of plastic.

The moisture impermeable support layer is important in that it isolates the pouch from the surrounding environment containing a certain amount of moisture and, therefore, prevents the moisture from being adsorbed onto the silica gel. However, in this application in the wound dressing composition of the invention, the outer casing no longer has the advantage of a substantially continuous surface.

The wound dressing of the invention may also be packaged in kit form for use in an outpatient setting. Such kits may comprise any dressing of the invention. The components of the kit are typically placed in moisture-proof polymeric plastic bags to maintain the dryness and sterility of the wound dressing and wound treatment composition. It is also desirable to provide suitable separate holding means for holding the wound dressing in contact with the wound as part of the kit.

In use, the wound dressing is applied to the wound in the usual manner with one permeable wall of the sachet in contact with the wound. The effect obtained with these two basic ingredients has been found to be significant. Silica gel itself is considered too active for practical use, however it is both fast and effective for absorbing exudate from a wound. Applicants believe that effective removal of such exudate is critical for rapid healing.

On the other hand, applicants have found that collagen itself acts too slowly, but is effective for absorbing and killing bacteria. The combined action of these two main components appears to be synergistic, as the rate of wound healing is significantly increased.

Typically, the wound dressing of the invention is replaced at regular intervals, for example every 4 to 6 hours, or in some cases once a day, depending on the condition of the wound.

It will be appreciated that many variations and modifications of wound treatment compositions and dressings are possible within the scope of the invention without departing from the scope of the invention.

Claims (11)

1. A wound dressing comprising a casing having an inner wall (5) for contact with a wound in use and an outer wall (6) remote from the wound, the inner wall (5) being perforated (7) to allow exudate or slough to pass therethrough, wherein a wound treatment composition (1) is contained within the casing, the wound treatment composition (1) comprising at least one absorbent or adsorbent compound in the form of silica gel, the wound dressing being characterised in that the silica gel is mixed with collagen.

2. The wound dressing of claim 1, wherein the inner wall of the outer casing is a plastic inner wall having a substantially smooth continuous plastic surface.

3. The wound dressing of claim 2, wherein the inner wall of the outer casing is a medical grade polypropylene film.

4. A wound dressing as claimed in claim 1, in which the outer wall of the sheath is a perforated (9) plastics film (8) having a layer of superabsorbent material (10) bonded to its side adjacent the inner wall.

5. The wound dressing of claim 1, wherein the wound treatment composition is contained in one or more prefabricated moisture-permeable sachets positioned in the outer sheath.

6. A wound dressing as claimed in claim 5 in which the sachet is formed from a moisture permeable material which is a non-woven fibrous polypropylene material.

7. The wound dressing of claim 1, wherein the casing is produced in the following manner: interconnecting each casing with a series of adjacent casings to form a continuous row of casings, the rows of casings being interconnected by regions (14) of sheet material forming the inner and outer walls of the casings, the regions (14) of sheet material being located around the casings, and the regions being fused together by thermal fusion at least along predetermined lines (13) to define the peripheral boundary of each casing.

8. A wound dressing as claimed in claim 7 in which the welds are made along two separate parallel lines to define a region (14) of sheet material between the sheaths themselves along which the sheaths can be separated from one another.

9. A wound dressing as claimed in any one of the preceding claims wherein the collagen is gelatin and in the wound treatment composition the gelatin is from 10% to 15% by weight and the silica gel is from 85% to 90% by weight.

10. A wound treatment composition, comprising in combination:

(a) a silicone gel that absorbs moisture on or around the wound; and

(b) collagen protein.

11. A wound treatment composition as claimed in claim 10 wherein the collagen is gelatin and in the wound treatment composition the gelatin is 10 to 15% by weight and the silica gel is 85 to 90% by weight.