WO2008135551A2

WO2008135551A2 - A filler with controlled absorption swell for wound bed cavity

Info

Publication number: WO2008135551A2
Application number: PCT/EP2008/055490
Authority: WO
Inventors: Chaabane Bougherara; Patrik Gavelin; Peter Kwok Hing Lam
Original assignee: Coloplast A/S
Priority date: 2007-05-03
Filing date: 2008-05-05
Publication date: 2008-11-13
Also published as: WO2008135551A3; WO2008135551A8

Abstract

The present invention relates to a product suitable for absorbing fluid from wounds during the healing process and a method for manufacturing such a product.

Description

A Fl LLER W l TH CONTROLLED ABSORPTI ON SW ELL FOR WOU N D BED CAVI TY

Field of the I nvention

This invention relates to a product suitable for absorbing fluid from wounds during the healing process.

Background of the invention

Various products have been used for absorbing fluids such as wound exudate, but they tend to be fibrous and are therefore prone to adhere to the wou nd and to leave bits in the wound.

I t is known from the prior art to use bits or individual discrete com ponents or balls or blocks as absorbent and arranging them on a string or in a net. The product in this form has a large wound contact surface enabling good fluid m anagem ent and release of actives. This form also allows the product to be tightly packed into a wound cavity and yet easily rem oved. The product can be cut to length to fit wounds of varying size.

EP 0575090 discloses a product suitable for absorbing wound exudate com prising a series of interconnected square or rectangular perforated bags m ade of a substance of m axim u m thickness 1 m m e.g. film , which is substantially non-adherent to a wound, wherein alginic acid or a salt thereof such as calcium alginate is housed in the bags, preferably in the form of sm all spheres. The film preferably com prises ethylene/ m ethyl acrylate copolym er. Alternatively, the product com prises a string along which beads of alginic acid or alginate are threaded.

US Patent No. 5470625 discloses an elongated segm ented wound packing product com prised of individual linked segm ents of hydrogel enclosed within a liquid perm eable pliable m aterial, the individual segm ents being connected in a strand-of-beads like configuration . US Patent No. 3095877 discloses as a surgical packing a nylon thread on which is spaced a plurality of equally spaced half inch diam eter balls, typically m ade of foam m aterial such as urethane foam or foam rubber.

Further background art m ay be found in US 3 797 496, US 4 1 20 299, US 1 997 467, US 5 833 642, US 5 470 625 and US 3 095 877.

The bits or individual discrete com ponents or balls or blocks according to the prior art are m anufactured in one process, which often require cutting and sorting.

The threads and the nets known in the prior art are necessary to string or connect the individual com ponents together. This is done in a separate process. I f twisting of the net is required, a further step of process is needed.

The threads and the nets are m ade of different m aterial from the absorbent com ponents to provide strength and con nectivity. Generally, these m aterials are not functional as absorbents.

The net or string is exposed in part or in full on the product when in use and m ay be m ade of harder m aterial, or with less skin friendly surfaces, thereby discom forting and aggravating the wound bed.

Such difficulties have been overcom e by the use of the absorbent product of the present invention . This product is m anufactured by a one step process, which is saving both tim e and m aterial. The product of the invention is giving absorbing ability to the whole length of the product. Furtherm ore, the absorbent surface of the product is soft and m oist, thereby giving these characteristics to the whole product, which m akes the product of the invention m ore user friendly.

Sum m ary of the invention

The present invention relates to a product suitable for absorbing fluid from wounds during the healing process and a m ethod for m anufacturing such a product. The product suitable for absorbing wound exudate comprising bits interconnected by a string, wherein the bits and the strings are consisting of the same absorbent material.

Brief description of the figures

FIG.1 is a top plan view of an embodiment of the invention and it illustrates the wound packing product of the invention.

FIG.2 is a top plan view thereof showing an embodiment of the invention where the cut sheets are assembled together.

FIG.3 illustrates a two-step cutting method of preparing the wound packing product of the invention.

FIG.4 illustrates a preferred embodiment of the wound packing product of the invention where the product is further strengthened by having a continuous net or string on the inside.

FIG.5 illustrates an extrusion and/or moulding method of preparing the wound packing product of the invention.

Detailed description of the invention

The present invention relates to a product suitable for absorbing fluid from wounds during the healing process. The product suitable for absorbing wound exudate comprising bits interconnected by a string, wherein the bits and the strings are consisting of the same absorbent material.

The product according to the present invention is manufactured by a one step process, which is saving both time and material.

The product of the invention comprises bits interconnected by a string (an interconnecting element/member). The bits and the strings are consisting of the same absorbent material. This allows the bits and the string to provide an identical absorption capacity, whereby the whole length of the product may have the same absorption capacity. In one embodiment the interconnecting member/element and the bits define a monolithic element, i.e. defining one element with out seams. In one embodiment the density and/or the buoyancy of the bits and the strings are substantially identical.

In one embodiment the product according to the present invention defines a plurality of bits (spheres/balls/dices/cubes) and a plurality of interconnecting members. In the latter embodiment, any two neighbouring bits are interconnected by an interconnecting member. Accordingly, each of the interconnecting members (except those defining one of the two ends of the string) is connected to two bits only.

The product of the invention can also be understood as a continuous string or 'sausage' having fat and thin segments where the thin segments provide extra flexibility for bending and folding, hence enhancing the flexibility of the entire product, as the strings/interconnecting members enable the product to be packed into cavities, e.g. of a wound. The fat segments may correspond to the bits/spheres/balls/dices/cubes and the thin segments may correspond to the string(s)/interconnecting member(s) .

The bits and string parts may be connected mechanically or chemically, preferably by one step moulding or extruding method.

The bits-and-string-product may be treated, if needed, to prevent adhesion to each other or to the wound bed. The treating material may be polyvinyl-alcohol, polyvinylpyrrolidone or any other coating with swelling properties known in the art.

The bits and strings may be cut to required size. The disadvantage as mentioned above having a product comprising two different materials has been eliminated by using the same absorbent material for the bits as well as for the strings.

Furthermore, the absorbent surface of the product is soft and moist, thereby giving these characteristics to the whole product, which makes the product of the invention more user friendly. At least a part of the user friendliness is achieved by the soft and moist surface of the produce, as it will be appreciated that a moist and soft surface is less or non painful to have inserted into, to wear in and to have removed from a wound relative to a hard and non-moist surface.

The absorbent material can be in the form of a foam or a hydrogel. In the context of the present invention the term foam shall be understood as an open or closed cell flexible material.

The absorption capacity of the absorbent material is greater than 25% of its own weight, preferably greater than 100% of its own weight. In one embodiment the absorption capacity is in the range 100-5000%, such as in the range 500- 2500%, such as in the range 1000-2000%

The absorbent hydrogel may preferably be of the type described in US Patent No.4593053, the entire content of which is incorporated herein by reference. These hydrogels are of the hot melt type as is fully described in US Patent No. 5002792, the entire content of which is incorporated herein by reference.

Other materials may also be used, not necessarily of the hot melt type, such as calcium alginate, polyethylene oxide, polyacrylates , hydrophilic urethane and polyvinylpyrrolidone, to name a few other hydrogels.

Non-hydrogels may also be used as the absorbent material. For example, sponge-like materials available from Avitar, Inc., of Cantor, Mass. under the trademark Hydrosorb.TM. may be used. Foam-like materials available from Acme United Corporation, Medical Products Division, of Fairfield, Conn.0640, under the trademark Lyofoam.RTM. may also be used. This is a specially treated polyurethane. Foam materials may include, but are not limited to, silicone, polyacrylates, polyethylene oxide, polypropylene oxide, and polyurethane. A preferred foam material to be used is available from Coloplast A/S under the trademark Biatain. The foam is preferably the open cell type.

Bits can take various forms. Thus, they can be spheres or rectangular. In general, by bit is meant any small discrete quantity, which needs not be regular in shape.

The shape of the bits can vary but preferred are substantially spherical, rectangular or square bits.

In one embodiment the bits are in the form of small spheres, and particularly spheres having a diameter of 1 mm to 50 mm, for example 5 mm. By "sphere" it is not meant that it has to be a geometrically perfect sphere. The string has a thickness or diameter 1 to 50% of that of the bits.

In another embodiment the product is made of a substance of maximum thickness 50 mm.

In one embodiment of the invention the product is further strengthened by having a continuous net, film or string on the inside of the absorbent material.

The strengthening string, film or net can be a thin length of cord, thread, twine, fibre, woven or non-woven, or similar material, a continuous or perforated film, and may be of natural or synthetic material. Thus it may be a nylon thread. It can be hydrophilic but not water soluble, for example cross-linked.

Examples of fibrous materials which may be used as the strengthening string, film, or net are polyolefins such as polyethylene, polypropylene and polybutylene homopolymers and copolymers, polyethers, polyurethanes, vinyl polymers such as polyvinylchloride, polyamides such as nylon, and polyesters. Other fibres include rayon and acrylic fibres. In a further embodiment the bits and/or the strings could contain active wound healing agents, for example growth factors, collagen, glycosaminoglycans, vitamins, antiseptic agents and enzyme debriders.

Referring to Figures 1 and 3, a method of preparing the product of the invention will be described in connection with one embodiment thereof. Figure 1 shows a series of bits interconnected by a string. The bits are illustrated as squares and the strings are illustrated as having the same length as the bits. These dimensions and forms can be varied in many ways according to the invention. In one embodiment of the invention foam sheets can be cut out to provide the st rings- and- bit s form where smaller segments which are more flexible than the broad segments connecting the latter together. Figure 3 illustrates a preferred method of cutting in 3-dimension by a two step cutting or rotating cutting. Any method of cutting known in the art can used for the cutting, for example by press and stamping out, heat or laser cutting.

In one embodiment of the invention a plurality of series of bits interconnected by a string are connected in a 2-dimension form of a net or in a 3-dimension form of a matrix.

Figure 2 is illustrating an embodiment of the invention where the cut sheets are assembled together by glue or by other means to provide higher volume. A film or net or string may be sandwiched between the layers for further strengthening.

Figure.4 illustrates a preferred embodiment of the wound packing product of the invention where the product is further strengthened by having a continuous net, film or string on the inside.

FIG.5 illustrates an extrusion and/or moulding method of preparing the wound packing product of the invention. This can be done in a continuous or batch process. The pre-formed absorbent material is put into a mould and activated to form, by crosslinking and foaming, a stable bits and string product. Examples

In the following different recipes suitable for manufacturing foam for use in the present invention are disclosed:

RECI PE ONE:

Hypol 2002 12 g from Dow chemical

Hypol 2060 8 g from Dow chemical

Distilled water 20 g

Tween 20/80 0.15 g Aldrich

RECI PE ONEA:

Hypol 2002 12 g from Dow chemical

Hypol 2060 8 g from Dow chemical

Distilled water 20 g

Tween 20/80 0 .15 g Aldrich lbuprofen 0 .14 g Aldrich

RECI PE ONE B:

Hypol 2002 12 g from Dow chemical

Hypol 2060 8 g from Dow chemical

Distilled water 20 g

Tween 20/80 0.15 g Aldrich

Alphasan 2.4 g Melliken RECI PETWO:

Lupranol 2042 30 .00 g from BASF

Voranol CP 1421 3 .00 g from BASF

Distilled water 0 .36 g

Polycat 17 0 .30 g from Air product

Silpur 9000 0.2 g from GE Bayer Silicone

Norsocryl SF 35 7 .45 g from Atofina

Lupranat MP 102 1 1.4 g from BASF

RECI PETHREE

MDI 14977-11A 130 g from Dow cl

Distilled Water 100 g

Tween 20/80 1 g from Aldrich

RECI PE FOUR.

Foam f MCF 03 from Corpura

RECI PE FIVE

MDI 14977-11A 1 10 g from Dow cl

Distilled Water 1 00 g

Tween 20/80 1 g from Aldrich Procedure for determination of retention and extension of foam manufactured using one of the above recopies

The retention and the extension may be determined using a procedure comprising the following steps:

1. providing a foam of material manufactured using one of the above recipes (the foam may be provided as a sheet of foam with a thickness of 3-4 mm);

2. punching a circular pad having a "dry diameter" of 43 mm (diameter of the pad in its dry state);

3. determining the weigh of the pad so as to determine a "dry weight";

4. inserting the pad into a Petri dish;

5. pouring approximately 30 ml of Solution A (8.298 g NaCI + 0.368 g CaCl2-2H2θ per litre of distilled water) into the Petri dish;

6. providing a cover/lit over the Petri dish;

7. leaveing the pad in the Solution A for at least 4 hours, preferably 24 hours and at a temperature of 37°C;

8. removeing the pad by means of tweezers;

9. allowing the pad to drip for 10 seconds;

10. determining the weigh of the pad (which have been soaked in Solution A) so as to determine an "absorption weight";

11. measuring the diameter at saturation so as to determine a "wet diameter" 12. placing the sample between 2 pieces of dry paper suitable for absorbing liquid present on the surface of the foam (It will be appreciated that the better the absorption capacity of the paper is, the more liquid may be absorbed);

13. inserting the two sheets of paper with the pad provided therein-between into plastic rollers at the speed of 30 RPM (the distance between the rollers shall be such that when no foam is provided between the rollers, the rollers physically contacted each other), so as to squeeze water out of the pad;

14. repeating step 13 and 14 until the pad has been rolled between new dry paper three times all in all.

15. determining the weight of pad so as to determine a "compressed weight";

16. calculating the retention in percent using the following formula:

(compressed weight - dry weight)

Retention [g/g] = 100 x

(absorption weight - dry weight)

17. calculating the expansion in percent using the following formula:

(wet diameter - dry diameter)

Expansion [%] = 10O x

(dry diameter)

It will be appreciated that the unit of each of the weight and the diameter, must be identical in the equations, i.e. the compressed weight, the dry weight and the absorption weight must be provided in the same unit, such as grams, and the wet diameter and the dry diameter must be provided in the same unit, e.g. millimetres. Example One:

Polyurethane foam spheres/balls were obtained by moulding at room temperature (20-25 degrees Celsius) for 3 minutes with a mixture based on RECIPE ONE.

The mould into which the mixture was poured during the moulding process was shaped such that the moulding process resulted in a plurality of spheres/balls each of which has a diameter of 10 mm. In the plurality of spheres/balls any two neighbouring spheres/balls were interconnected by an interconnecting member having a thickness (a diameter in the case of circular interconnecting member) of 1 mm. The length of each of the interconnecting members were 3 mm. Accordingly, the spheres/balls were spaced apart by a distance of 3 mm.

The following table illustrates the retention and the extension of the balls of Example One:

The retention and extension were determined by means of the abovementioned method. The retention is indicated in the terms of "grams of liquid per grams of foam" [g/g]. The extension is indicated in terms of extension of volume as a result of absorption of fluid.

Example Two:

Example Two is identical to Example One, with the difference that the foam was based on RECIPE ONE A, and thus contained a pain reducing agent such as Ibuprofen.

The following table illustrates the retention, the extension and the content of Ibuprofen of the balls of Example Two:

The content of lbuprofen content was measured by HPLC, using Dionex Ultimate 3000 equipment

The retention and the extension were determined by means of the abovementioned method.

Example Three

Example Three is identical to Example One, with the difference that the foam was based on RECIPE ONE B, and thus contained an anti microbial ingredient such as silver complex (Ag⁺).

The following table illustrates the retention, the extension and the content of Ag⁺ of the balls of Example Three:

The content of Ag⁺ was determined by atomic absorption using a Perkin Elmer equipment, type "AAnalyst 100".

Example Four Example Four is identical to Example One, with the difference that the foam was based on RECI PE THREE.

The following table illustrates the retention and the extension of the balls of Example Four:

Example Five:

Example Four is identical to Example One, with the difference that the foam was based on RECIPE TWO and that the foam moulding process took place at a temperature of 50 degrees Celsius and not at room temperature, i.e. the temperature of the mould into which the foam was poured/injected had a temperature of 50 degrees Celsius.

The following table illustrates the retention and the extension of the balls of Example Five:

Example Six: A rod-shaped foam element with a diameter of 10 mm were obtained by moulding a polyurethane masse based on RECIPE ONE at room temperature.

Subsequent to the moulding process the rod-shaped foam element were cut by means of a cutting tool, into a monolithic element (i.e. one single element with out seams) defining a plurality of spheres/balls interconnected by a plurality of interconnecting members.

In Example Six the diameter of each of the spheres/balls were identical to the diameter of the rod-shaped foam element i.e. 10 mm. The monolithic element defined a plurality of interconnecting members, each of which interconnected two neighbouring spheres/balls. Each of the interconnecting members had a length of 3 mm. The cross-section of each of the interconnecting members was rectangular such that one side of the rectangular cross-section was 10 mm and another transverse side was 1 mm.

The following table illustrates the retention and the extension of the balls of Example Six:

Example Seven:

Example Seven is identical to Example Six, with the difference that the polyurethane foaming masse was based on RECIPE FIVE.

The following table illustrates the retention and the extension of the balls of Example Seven:

Example Eight:

The foam of Example Eight was based on Corpura Foam MCF 03. The foamed material were cut so as to from a monolithic element comprising a plurality of dices. Any two neighbouring dices were interconnected by an interconnecting member. Each of the dices had the following dimensions: 10 mm x 10 mm x 10 mm. The interconnecting members each of which interconnected two neighbouring dices were 3 mm long and had a rectangular cross-section with the dimensions 3 mm x 2 mm.

The following table illustrates the retention and the extension of the balls of Example Eight (comprising Corpura Foam MCF 03, Batch 0803121238):

Example Nine:

Starting from a 10 mm thick sheet of foam of Corpura, a welding tool was utilised to form a plurality of spheres/balls each of which had a diameter of 10 mm. Any two neighbouring spheres/balls were interconnected by an interconnecting member.

Each of the interconnecting members was 3 mm long and had a rectangular cross section with the dimensions 1mm x 3mm.

The following table illustrates the retention and the extension of the balls of Example Nine (comprising Corpura Foam MCF 03, Batch 0803121238):

Claims

CLAI MS

1. A product suitable for absorbing wound exudate comprising bits interconnected by a string, wherein the bits and the strings are consisting of the same absorbent material.

2. The product according to claim 1 wherein the bits and string are of the same continuous phase.

3. The product according to any of the claims 1-2 wherein the absorbent material is substantially non-adherent to a wound.

4. The product according to any of the claims 1-3 wherein the density of the strings is substantially identical to the density of the bits.

5. The product according to any of the claims 1-4 wherein the absorbent material is a hydrogel.

6. The product according to any of the claims 1-4 wherein the absorbent material is a foam.

7. The product according to any of the claims 1-4 wherein the absorbent material is selected from the group of: polyethylene oxide, hydrophilic urethane, silicone, polyacrylics, polyvinylpyrrolidone, alginic acid or a salt thereof preferably calcium alginate, polyurethane foam.

8. The product according to any one of the preceding claims wherein the bits are substantially in the form of spheres.

9. The product according to any of the claims 1-7 wherein the bits are substantially square or rectangular in shape.

10. The product according to any one of the preceding claims wherein the product is made of a substance of maximum thickness or diameter 1 to 50 mm for the bits part, and 1 to 50% of that for the string part.

11. The product according to any one of the preceding claims wherein the product is further strengthened by having a continuous net, film or string on the inside of the absorbent material.

12. The product according to any one of the preceding claims wherein the bits and/or strings contain active wound healing agent.