U.S. patent application number 11/255956 was filed with the patent office on 2006-03-16 for antimicrobial composite.
This patent application is currently assigned to Beiersdorf AG. Invention is credited to Harald Buttner, Peter Hilfenhaus, Heike John.
Application Number | 20060057369 11/255956 |
Document ID | / |
Family ID | 33542150 |
Filed Date | 2006-03-16 |
United States Patent
Application |
20060057369 |
Kind Code |
A1 |
Hilfenhaus; Peter ; et
al. |
March 16, 2006 |
Antimicrobial composite
Abstract
A wound covering article comprises an antimicrobial composite
which comprises a first, liquid-permeable layer and a second layer
over the first layer, An antimicrobial metal in elemental form is
present between the first and second layers. The article further
comprises a backing material arranged on the second layer. This
Abstract is neither intended to define the invention disclosed in
this specification nor intended to limit the scope of the invention
in any way.
Inventors: |
Hilfenhaus; Peter; (Hamburg,
DE) ; John; Heike; (Neu Wulmstorf, DE) ;
Buttner; Harald; (Neu Wulmstorf, DE) |
Correspondence
Address: |
GREENBLUM & BERNSTEIN, P.L.C.
1950 ROLAND CLARKE PLACE
RESTON
VA
20191
US
|
Assignee: |
Beiersdorf AG
Hamburg
DE
|
Family ID: |
33542150 |
Appl. No.: |
11/255956 |
Filed: |
October 24, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10654949 |
Sep 5, 2003 |
|
|
|
11255956 |
Oct 24, 2005 |
|
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Current U.S.
Class: |
428/343 ;
428/346; 428/354; 428/355AC; 428/356 |
Current CPC
Class: |
B32B 2305/38 20130101;
A61F 13/8405 20130101; B32B 27/04 20130101; Y10T 428/2813 20150115;
A61L 2300/104 20130101; A61L 15/18 20130101; Y10T 428/2891
20150115; Y10T 428/2857 20150115; B32B 27/08 20130101; Y10T 428/28
20150115; Y10T 442/10 20150401; Y10T 442/109 20150401; A61L
2300/102 20130101; Y10T 442/178 20150401; B32B 2535/00 20130101;
Y10T 442/2525 20150401; B32B 7/12 20130101; Y10T 442/183 20150401;
A61L 15/46 20130101; Y10T 442/164 20150401; A61L 2300/608 20130101;
B32B 3/26 20130101; A61L 2300/404 20130101; Y10T 442/169 20150401;
B32B 27/32 20130101; B32B 27/12 20130101; A61F 13/0203 20130101;
B32B 2311/08 20130101; Y10T 156/10 20150115; B32B 2311/24 20130101;
B32B 15/08 20130101; Y10T 428/2848 20150115; A61F 2013/00748
20130101; B32B 2305/026 20130101; B32B 2307/54 20130101; A61F
2013/00936 20130101; A61F 2013/0091 20130101; B32B 2307/726
20130101; A61F 13/0276 20130101; Y10T 442/172 20150401; B32B
2323/04 20130101 |
Class at
Publication: |
428/343 ;
428/354; 428/355.0AC; 428/346; 428/356 |
International
Class: |
B32B 7/12 20060101
B32B007/12; B32B 15/04 20060101 B32B015/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 23, 2003 |
DE |
103 28 261.0 |
Claims
1. A wound covering article comprising an antimicrobial composite
which comprises a first, liquid-permeable layer and a second layer
over the first layer, wherein an antimicrobial metal in elemental
form is present between the first and second layers, the article
further comprising a backing material arranged on the second
layer.
2. The article of claim 1, wherein the backing material carries an
adhesive on a surface which faces the second layer of the
composite.
3. The article of claim 2, wherein the adhesive comprises one of a
UV-curable acrylic adhesive and a rubber-based hot melt
adhesive.
4. The article of claim 1, wherein the backing material comprises
at least one of a polyester nonwoven and a polyethylene film.
5. The article of claim 1, wherein the first layer comprises a
foramenous material.
6. The article of claim 1, wherein the first layer comprises at
least one of a perforated film and a mesh.
7. The article of claim 6, wherein the first layer comprises a
polyethylene mesh.
8. The article of claim 1, wherein the second layer is one of a
liquid-permeable layer and a liquid-absorbing layer.
9. The article of claim 8, wherein the second layer is a
liquid-absorbing layer.
10. The article of claim 9, wherein the second layer comprises a
textile sheet.
11. The article of claim 8, wherein the antimicrobial metal
comprises Ag and alloys thereof.
12. The article of claim 1, wherein the antimicrobial metal is
provided as a coating on at least one of the surfaces of the first
and second layers.
13. The article of claim 1, wherein the antimicrobial metal is
present as a layer which comprises the antimicrobial metal and is
arranged between the first and second layers.
14. The article of claim 1, wherein the article has a sheet-like
structure.
15. The article of claim 1, wherein the first layer has a silver
coating on a surface thereof which faces the second layer.
16. The article of claim 15, wherein an intermediate aluminum layer
is arranged between the silver coating and the first layer.
17. A wound covering article comprising an antimicrobial composite
which comprises a first, liquid-permeable layer and a second,
liquid-absorbing layer over the first layer, wherein silver in
elemental form is present between the first and second layers, the
article further comprising a backing material arranged on the
second layer.
18. The article of claim 17, wherein the silver is provided as a
coating on one of the surfaces of the first and second layers.
19. The article of claim 18, wherein substantially no silver is
present on external surfaces thereof.
20. A wound covering article comprising an antimicrobial composite
which comprises a first, liquid-permeable layer and a second,
liquid-absorbing layer over the first layer, wherein a coating of
silver in elemental form is present on a surface of the first layer
that faces the second layer, the article further comprising a
backing material arranged on the second layer and being
substantially free of elemental silver on external surfaces
thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a divisional of U.S. application
Ser. No. 10/654,949, filed on Sep. 5, 2003, which claims priority
under 35 U.S.C. .sctn. 119 of German Patent Application No. 103 28
261.0, filed on Jun. 23, 2003. The disclosures of these
applications are expressly incorporated by reference herein in
their entireties.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to antimicrobial composites
which may be used, in particular, as wound coverings, dressings,
cloths, and the like. By coating one side of a liquid-permeable
material with an antimicrobial metal such as silver and laminating
the resultant material to a material such as a liquid-absorbing
nonwoven material with the metal coating facing the
liquid-absorbing material, the abrasion of metal particles may be
prevented while at the same time, the antimicrobial and
disinfectant effect of the metal coating is retained.
[0004] 2. Discussion of Background Information
[0005] Treating and healing bacterially contaminated skin and
wounds, or infected skin and wounds is a major challenge to
medicine and the natural sciences. Poorly healing and chronic
wounds frequently become populated by a wide variety of
microorganisms that considerably delay healing and sometimes even
prevent healing altogether. Frequently, in the case of acute wounds
that are caused by trauma, surgical intervention or even just
simple injury, the penetration and infection by pathogenic
microorganisms can, however, not completely be prevented.
[0006] Various possibilities are described for removing
microorganisms from the contaminated or infected tissue of a wound
and/or for killing the microorganisms. In addition to the oral
administration of antibiotics, the removal of pathogenic
microorganisms from a wound may be achieved, in accordance with the
prior art, by the topical application of a disinfectant or an
antibiotic. However, antiseptics and antibiotics are cytotoxic; in
addition, many pathogenic strains have developed resistances to
antibiotics.
[0007] An example of the known antimicrobial and/or prophylactic
treatment of contaminated or infected wounds is the use of oxidants
such as tincture of iodine, or of antiseptics such as ointments
which contain silver sulfadiazine.
[0008] For a very long time, silver has been the agent of choice
for treating infections, due to its broad bactericidal and
fungicidal effect. In addition to its broad range of activity,
silver is effective in minute, i.e., trace amounts (oligodynamic
effect). Since the amounts of silver are so small, the tolerance is
excellent. For example, silver aerosols, silver-containing
solutions, ointments or tablets, etc. are widely used as
antiseptics.
[0009] Silver-containing products are also used in the form of
corresponding antimicrobially treated or impregnated wound
dressings and wound care materials. The use of silver-containing
zeolites, glasses and zirconyl phosphates, and also of silver in
elemental or nanocrystalline form, is known as well.
[0010] Basically, there are two forms used for the administration
of silver (ions), i.e., forms in which the silver ions are present
in the product per se, and forms in which the ionic form of silver
is generated by the oxidation of elemental silver. The first case
essentially involves a dissolution or ion-exchange process. This
makes the silver ions rapidly available, but the amount of silver
ions in the preparation drops quickly as well. To provide a
sufficient amount of silver to counteract this disadvantage is not
without problems. For example, the cytotoxicity of silver ions
limits the maximum acceptable amount thereof that can be used in a
product.
[0011] Another disadvantage is that silver is deactivated by
proteins, other complex-formers, or in the presence of ions that
form scarcely-soluble silver salts. These conditions doubtlessly
exist in wound fluids. In contrast, the release of silver from
"elemental" silver (silver metal) is slower and occurs over a
longer period, but takes place continuously. Accordingly, a
sufficient amount of silver ions that is harmless to the user can
always be released from the reservoir of elemental silver, the
amount of silver ions depending on whether more or less of these
ions can be released by equilibrium processes. The release of
silver is, therefore, "as needed," and the release of an effective
quantity of silver is ensured.
[0012] An overview of known antimicrobial, silver-containing wound
care materials is given in DE-A1-19958458.
[0013] A commercially available wound care product with
antimicrobial properties is known under the name of Arglaes.RTM..
Its mode of action is based on "slow-release polymer" technology
that causes a slow but constant release of silver ions in the moist
milieu of the wound (Biomed. Mat., November 1995; Health Industry
Today, 1 Nov. 1997, Vol. 58, No.11).
[0014] DE-A1-19958458 discloses wound coverings comprising a
synthetic polymer material which contains metal ion-containing
zeolites.
[0015] Silver-containing glasses that have an antimicrobial effect
are known from EP-A1-1116698 and EP-A1-1116700. These glasses are
embedded in thermoplastic polymers that are used in a wide variety
of forms for household and hygienic applications such as wallpaper,
cutting boards, etc.
[0016] U.S. Pat. Nos. 5,753,251 and 5,681,575 describe
antimicrobial coatings with so-called nanocrystalline silver that
are formed on a medical product by depositing metals such as, e.g.,
silver from a gas phase. The antimicrobial effect is based on the
release of ions, atoms, molecules or clusters from a disordered
metal lattice when the silver is in contact with water or
alcohol-based electrolytes. The corresponding product is known
under the name Acticoat.RTM.. One of the disadvantages of this
product is the visibly identifiable silver abrasion that causes a
black discoloration of the covered skin area.
[0017] U.S. Pat. No. 2,934,066 describes a wound covering coated
with metals, especially silver, which is reported to have a
disinfecting effect.
[0018] The entire disclosures of the documents cited above, as well
as those of all other documents mentioned in the present
specification, are expressly incorporated by reference herein as if
each of these documents in its entirety were part of the present
specification.
[0019] Wound coverings comprising a non-woven material that is
covered with a silver-coated polyethylene mesh are also known,
e.g., Katomed.RTM..
[0020] In all of the known disinfectant wound dressings which
comprise a coating of elemental or nanocrystalline silver, the
silver coating is intended to directly contact the wound. A
disadvantage of these disinfecting materials is, therefore, that
upon their contacting of the skin or wound they give rise to an
abrasion and release of small particles of elemental silver. These
particles form inclusions in the skin or wound, so-called
granulomas, and can lead to complications during wound healing.
Furthermore, due to the generated black discoloration, the
aesthetic acceptance of corresponding products among users is very
low.
[0021] It would be desirable to have available a material, e.g., a
skin or wound dressing, which does not show the disadvantages of
the known materials, but nevertheless shows antimicrobial
activity.
SUMMARY OF THE INVENTION
[0022] The present invention provides an antimicrobial composite
comprising a first, liquid-permeable layer and a second layer
arranged on the first layer. An antimicrobial metal in elemental
form is present between these layers. Moreover, substantially none
of this antimicrobial metal in elemental form is present on
exterior surfaces of the composite.
[0023] In one aspect of the composite, the first layer may comprise
a foramenous structure, and preferably comprises a hole structure
and/or a mesh structure. For example, the first layer may comprise
a perforated film and/or a mesh.
[0024] In another aspect of the composite, the first layer may
comprise an organic polymer, preferably, a polyolefin such as,
e.g., polyethylene and/or polypropylene
[0025] In yet another aspect, the first layer may comprise a
polyethylene mesh.
[0026] In a still further aspect, the first layer preferably
comprises openings having a size of from about 250 .mu.m to about
1400 .mu.m, e.g., from about 400 .mu.m to about 700 .mu.m. In one
embodiment, the openings may have a substantially triangular shape
and/or may provide an open area of from about 15% to about 60% of
the surface area of the first layer.
[0027] In another aspect of the composite, the first layer may have
a thickness of from about 0.02 mm to about 0.8 mm, e.g., of from
about 0.05 mm to about 0.5 mm.
[0028] In a still further aspect, the second layer is a
liquid-permeable layer or a liquid-absorbing layer.
[0029] In another aspect, the second layer may comprise a
perforated film and/or a mesh.
[0030] In yet another aspect, the second layer may comprise an
organic polymer. The organic polymer may comprise a polyolefin. For
example, the second layer may comprise a polyethylene mesh.
[0031] In a still further aspect of the composite of the present
invention, the second layer preferably has a thickness of from
about 0.02 mm to about 2.5 mm.
[0032] In another aspect, the second layer may be a
liquid-absorbing layer. This layer may have a liquid-absorbing
capacity of from about 300 g/m.sup.2 to about 2000 g/m.sup.2, e.g.,
from about 400 g/m.sup.2 to about 1000 g/m.sup.2. For example, the
liquid-absorbing layer may comprise a textile sheet, which textile
sheet may in turn comprise a nonwoven, a fleece, a woven fabric, a
knit and/or a felt.
[0033] In a still further aspect, the second layer may comprise
fibers and/or yarns.
[0034] In another aspect, the second layer may comprises viscose,
polyolefin (e.g., polyethylene and/or polypropylene) and/or
polyester.
[0035] In another aspect of the composite, the second layer
preferably has a thickness of from about 0.3 mm to about 2.4 mm,
e.g., from about 0.5 mm to about 1.4 mm and/or an area weight of
from about 80 g/m.sup.2 to about 200 g/m.sup.2.
[0036] In a still further aspect, the second layer may comprise a
superabsorber, for example, a superabsorber comprising a polymer
having recurring units derived from acrylic acid and derivatives
thereof. The superabsorber may be present in an amount of from
about 0.01% to about 40% by weight, based on the weight of the
second layer.
[0037] In another aspect of the composite of the present invention,
the antimicrobial metal preferably comprises at least one of Ag,
Au, Pd, Pt, Cu, Ir, Zn, Sn, Sb, Bi and/or an alloy comprising one
or more of these metals. Preferably, the antimicrobial metal
comprises Ag and/or an alloy thereof.
[0038] In yet another aspect of the present composite, the
antimicrobial metal may be provided as a coating on at least one of
the surfaces of the first and second layers.
[0039] In another aspect of the composite, the antimicrobial metal
may be present as a layer which comprises the antimicrobial metal
and is arranged between the first and second layers.
[0040] In a still further aspect, the composite preferably has a
sheet-like (web-like) structure.
[0041] In yet another aspect of the composite of the present
invention, the antimicrobial metal (e.g., silver) preferably is
present in an amount of from about 1 mg/m.sup.2 to about 1
g/m.sup.2 of composite, e.g., in an amount of from about 10
mg/m.sup.2 to about 600 mg/m.sup.2 of composite, more preferably in
an amount of from about 50 mg/m.sup.2 to about 450 mg/m.sup.2 of
composite, e.g., in an amount of from about 60 mg/m.sup.2 to about
80 mg/m.sup.2 of the composite.
[0042] In another aspect of the composite of the present invention,
the first layer has a silver coating on the side (surface) thereof
which faces the second layer and/or the second layer has a silver
coating on the side (surface) thereof which faces the first layer.
In yet another aspect, an intermediate layer is arranged between
the silver coating and the first layer. The intermediate layer
preferably comprises aluminum.
[0043] In yet another aspect of the composite, the composite
preferably has an area weight of from about 50 g/m.sup.2 to about
300 g/m.sup.2, e.g., from about 80 g/m.sup.2 to about 160
g/m.sup.2, and/or a thickness of from about 0.4 mm to about 2.5 mm,
e.g., from about 0.5 mm to about 1.4 mm, and/or a peeling strength
of from about 0.05 N/cm to about 1.5 N/cm, e.g., from about 0.15
N/cm to about 0.8 N/cm, and/or a maximum tensile strength of from
about 10 N/cm to about 40 N/cm, and/or a 24-hour release of the
antimicrobial metal (e.g., silver) of from about 0.05 mg/m.sup.2 to
about 3 mg/m.sup.2 of composite, e.g., of from about 0.1 mg/m.sup.2
to about 2 mg/m.sup.2 of composite and/or a size of at least about
0.5 cm.sup.2 and/or a size of not higher than about 1 m.sup.2.
[0044] The present invention also provides a wound covering
article, a skin care article and a diaper, all of which comprise
the above composite, including all of the various aspects
thereof.
[0045] The wound covering article, for example, may further
comprise a backing material arranged on the second layer of the
composite. The backing material may carry an adhesive, e.g., a
UV-curable acrylic adhesive or a rubber-based hot melt adhesive, on
the side thereof which faces the second layer. Furthermore, the
backing material preferably comprises a polyester nonwoven and/or a
polyethylene film.
[0046] The present invention also provides a method of covering a
wound. The method comprises placing the above wound covering
article, including the various aspects thereof, on the wound so
that the first layer of the composite contacts the wound.
[0047] The present invention also provides a method of covering a
wound. The method comprises providing a material which comprises a
liquid-permeable layer and an antimicrobial metal in elemental form
associated with this layer (e.g., coated with the metal and/or
having the metal incorporated therein and/or being in (direct)
contact with the metal, etc.), and placing the material on the
wound so that a surface of the liquid-permeable layer which is
substantially free of the antimicrobial metal in elemental form
contacts the wound.
[0048] In one aspect of the method, the liquid-permeable layer
preferably comprises a foramenous material, e.g., a hole and/or a
mesh structure. For example, the liquid-permeable layer may
comprise a perforated film and/or a mesh, e.g., a polyolefin
mesh.
[0049] The present invention also provides a process of making an
antimicrobial composite as set forth above. The process comprises
bonding together a first, liquid-permeable material and a second
material which is liquid-permeable and/or liquid-absorbing. At
least one of the first and second materials is coated with an
antimicrobial metal in elemental form on a side (surface) thereof
which faces the other material, whereas substantially no
antimicrobial metal in elemental form is present on the exterior
surface of the composite.
[0050] In one aspect, the process may comprise providing a
liquid-permeable, sheet-like material, coating one side of the
material with the antimicrobial metal and bonding a
liquid-absorbing material to that side of the liquid-permeable
material which has the antimicrobial metal thereon. The
liquid-permeable material preferably comprises a hole and/or a mesh
structure. In another aspect of the process, the liquid-permeable
material may be coated with the metal by a technique which
comprises vapor deposition, e.g., by vacuum evaporation,
sputtering, ion-beam assisted deposition, ion plating or magnetron
sputtering.
[0051] In another aspect of the process of the present invention,
the liquid-permeable material has an intermediate coating on that
side thereof which is to be coated with the antimicrobial metal.
The intermediate coating preferably comprises aluminum in metallic
form.
[0052] In a still further aspect of the present process, the
liquid-absorbing material and the liquid-permeable material are
bonded to each other by lamination under heat and/or pressure,
gluing, welding, and/or sewing.
[0053] As mentioned above, the first layer of the composite of the
present invention is a liquid-permeable layer. The term
"liquid-permeable" as used in the present specification and the
appended claims is interchangeable with the term "fluid-permeable"
and denotes a material which is capable of allowing liquid (fluid)
such as water, wound secretions (wound exudate) etc., present on
one side of the material to get to the opposite side of the
material, irrespective of the way and/or mechanism through which
this is accomplished. Accordingly, any material which is not
completely impervious to liquid (fluid) is "liquid-permeable" for
the purposes of the present invention. In this regard, it should be
noted that a liquid-absorbing material may become liquid-permeable
once the liquid absorbing capacity of the material is exceeded.
Preferably, the liquid-permeable material has a foramenous
structure, e.g., a hole or mesh structure. Non-limiting examples of
corresponding materials are a perforated film and a mesh.
[0054] The material of the first layer will usually comprise one or
more substantially bioinert materials, e.g., a (natural,
semisynthetic or synthetic) organic polymer, preferably, a
polyolefin such as, e.g., polyethylene and/or polypropylene.
However, materials different from organic polymers may be used as
well, as long as they can be made to be--or already
are--liquid-permeable. If the composite of the present invention is
to be used in wound-care applications, the material is preferably
substantially non-adhering to the wound.
[0055] Particularly in cases where the liquid-permeable material
comprises a net, the openings thereof preferably have an (average)
size (=length of the longest bisector) of at least about 250 .mu.m,
e.g., at least about 400 .mu.m, and not higher than to about 1400
.mu.m, e.g., not higher than about 1000 .mu.m, or not higher than
about 700 .mu.m. The openings may be of any shape such as, e.g.,
circular, triangular, rectangular, etc., and different shapes
and/or different sizes of openings may be present in the same
material. Preferably, the open area created by these openings is at
least about 15%, e.g., at least about 25%, and not more than about
60%, e.g., not more than about 50%, of the surface area of the
first layer. The same applies to other liquid-permeable structures
such as, e.g., perforated films, although in this case the size of
the hole openings may be by far larger than those usually
encountered with a net structure (e.g., up to about 3 mm or even
larger). Holes may be created (e.g., in a film) by many different
techiques, e.g., by mechanical perforation, punching, embossing,
flame-perforation, etc. Moreover, holes may be present in the
material from the beginning, e.g., in the case of nonwovens (e.g.,
spun bonded nonwovens), and woven or knitted fabrics.
[0056] The first layer will usually have a thickness of at least
about 0.02 mm, e.g., at least about 0.05 mm, or at least about 0.1
mm. Usually the thickness of the first layer will be not higher
than about 0.8 mm, e.g., not higher than about 0.5 mm, or not
higher than about 0.3 mm. It should be noted that while it is
currently preferred for the first layer to be composed of a single
layer, the first layer of the composite of the present invention
may itself be a composite of two or more individual layers (e.g., a
combination of a perforated film and a mesh), in which case the
above thickness values refer to the entire first layer. The unit
area weight of the first layer, including any antimicrobial metal
which may be combined therewith (in particular, silver), preferably
is in the range of from about 10 g/m.sup.2 to about 40 g/m.sup.2,
e.g., about 25 g/m.sup.2 (as determined by DIN EN 29073-1).
[0057] It should also be noted that the first layer of the
composite of the present invention may have a variety of substances
on the surface thereof which is to contact the wound, provided
these substances do not interfere to any significant extent with
the liquid-permeability of the layer and the antimicrobial effect
exerted by the metal. Non-limiting examples of such substances are
compounds and compositions which promote wound healing and/or have
a skin care effect.
[0058] Non-limiting examples of preferred materials for use in or
as the first layer of the composite of the present invention are
polyethylene nets available under the trade name Delnet.RTM.
(Applied Extrusion Technologies, Wilmington, Del.). These nets are
produced by extrusion, embossing and stretching of films. A huge
variety of these nets is commercially available and may be produced
by altering the polymer blend, the melt temperature, the embossing
pattern, and the stretch ratio.
[0059] The second layer of the composite of the present invention
will usually be liquid-absorbing, or at least liquid-permeable.
Where the second-layer is (merely) liquid-permeable, the second
layer may be the same as, or similar to the first layer, and in
this case the above comments with respect to the first layer may be
referred to with respect to properties, structure, etc. of the
second layer.
[0060] The second layer of the composite of the present invention
preferably is a liquid-absorbing layer. The term "liquid-absorbing"
as used in the present specification and in the appended claims
denotes a material which is capable of not only taking up a certain
amount of liquid (fluid), but also of retaining the liquid within
its structure under atmospheric pressure. Usually, a
liquid-absorbing material will be capable of retaining an amount of
liquid which equals at least about 5%, preferably at least about
10% of its own weight.
[0061] The liquid-absorbing capacity of the preferred
liquid-absorbing second layer of the composite of the present
invention (determined according to DIN 53923) will usually be at
least about 300 g/m.sup.2, e.g., at least about 400 g/m.sup.2, or
at least about 500 g/m.sup.2, but will usually not be higher than
about 2000 g/m.sup.2, e.g., not higher than about 1500 g/m.sup.2,
not higher than about 1000 g/m.sup.2, or not higher than about 800
g/m.sup.2. However, higher liquid-absorbing capacities than those
given above may be more appropriate in certain cases, for example,
for compresses for use with larger wounds.
[0062] Where the second layer is liquid-absorbing, the second layer
may be composed of any material that is liquid-absorbing and is
compatible with the intended use of the composite. Preferably, the
liquid-absorbing material will be substantially bioinert. For
example, the second layer may comprise a textile sheet and/or a
foam, e.g., a polyurethane foam. The textile sheet may comprise, by
way of non-limiting example, a nonwoven, a fleece, a woven fabric,
a knit and/or a felt. Preferred examples of the liquid-absorbing
material include nonwovens, e.g., nonwovens which are bonded by
various technologies such as, e.g., thermal bonding, stitch-bonding
(Malivlies, Maliwatt), carding, spun-lacing, melt blowing, etc.
[0063] By way of non-limiting example, the second layer may
comprise one or more natural, semisynthetic and/or synthetic
materials such as, e.g., viscose, cellulose and derivatives
thereof, polyolefins (e.g., polyethylene and/or polypropylene),
polyesters, polyetheresters, polyamides, polyurethanes,
hydrocolloids, hydrogels, and in general, materials which are
conventionally used for making wound coverings/dressings.
[0064] The second layer of the composite of the present invention
preferably has a thickness of at least about 0.3 mm, e.g., at least
about 0.4 mm, or at least about 0.5 mm. The thickness will usually
be not higher than about 2.4 mm, e.g., not higher than about 2.0
mm, or not higher than about 1.4 mm. Like in the case of the first
layer, the second layer of the composite of the present invention
may itself be a composite of two or more individual layers (by way
of non-limiting example, a combination of two layers or sheets of
different liquid-absorbing materials such as, e.g, a foam and a
textile sheet), in which case the above values (and those given
below) refer to the entire second layer.
[0065] The desirable area weight of the second layer of the
composite of the present invention depends on the intended use and
the type of lamination. For standard bandage products for treating
conventional wounds the area weight of the second, liquid-absorbing
layer (e.g., the nonwoven), as determined according to DIN EN
29073, will usually be not lower than about about 80 g/m.sup.2,
e.g., not lower than about 100 g/m.sup.2, and be not higher than
about 200 g/m.sup.2, e.g., not higher than about 150 g/m.sup.2, or
not higher than about 130 g/m.sup.2. An area weight of about 125
g/m.sup.2 is particularly preferred. In certain cases higher area
weights than those indicated above may be more appropriate, for
example, for compresses for use with larger wounds.
[0066] Additionally, the second (liquid-absorbing) layer may
comprise one or more superabsorbers such as, for example,
water-insoluble, cross-linked polymers that can swell and form
hydrogels to absorb and store large amounts of liquid (e.g.,
water), even under pressure. A non-limiting example of a suitable
superabsorber is a polymer which comprises recurring units derived
from acrylic acid and derivatives thereof. When present at all, the
superabsorber(s) will usually be present in an amount of from about
0.01% to about 40% by weight, based on the weight of the second
layer.
[0067] The composite of the present invention comprises one or more
antimicrobial metals such as, e.g., Ag, Au, Pd, Pt, Cu, Ir, Zn, Sn,
Sb, Bi, and alloys comprising one or more of these metals. A
particularly preferred metal is silver. The term "antimicrobial" as
used in the present specification and the appended claims is to be
understood in its broadest sense, and is inclusive of terms like
"disinfectant", "antibacterial", "antifungal" etc. In particular,
"antimicrobial" denotes activity against pathogenic microorganisms
of any kind.
[0068] The antimicrobial metal in elemental form may be present
between the first and second layers of the composite of the present
invention in any form which ensures that metal (ions) will be
present on the external surface of the first layer (opposite the
surface that faces the second layer) when this surface is contacted
with (aqueous) liquid (water, liquid electrolyte, wound exudate
etc.) for a sufficient period of time. Accordingly, the expression
"present between the first and second layers" as used in the
present specification and the appended claims does not exclude, but
rather includes, composites in which the antimicrobial metal is
present within the first layer and/or within the second layer
instead of, or in addition to, its presence between the layers. By
way of non-limiting example, the first layer of the composite of
the present invention may be composed of a combination of two
individual liquid-permeable layers (e.g., a mesh and a perforated
film or two perforated films), and the antimicrobial metal may be
sandwiched between (e.g., be present at the interface of these two
individual layers. Thus, the present invention encompasses any
composite wherein the antimicrobial metal in elemental form is
present within the composite, but substantially no antimicrobial
metal in elemental form is present on exterior surfaces of the
composite. "Substantially no antimicrobial metal in elemental form
is present on exterior surfaces of the composite" means that no
more than trace amounts of antimicrobial metal, in particular,
amounts which by themselves will not give rise to a noticeable
antimicrobial effect, are present on exterior surfaces of the
composite.
[0069] In a preferred embodiment of the composite of the present
invention, the antimicrobial metal is present as a coating on at
least one of the surfaces of the first and second layers,
preferably (at least) on one of the surfaces of the first layer,
although a corresponding coating or the like may also be present on
one or both sides of the second layer.
[0070] The antimicrobial metal may be present as such (i.e.,
without any other materials), but it may also be present in any
other suitable form, for example, as a layer which comprises the
antimicrobial metal and other materials such as, e.g., in the form
of a porous polymer matrix which contains embedded antimicrobial
metal.
[0071] The antimicrobial metal (e.g., silver) will usually be
present in an amount of at least about 1 mg/m.sup.2, e.g., at least
about 10 mg/m.sup.2, at least about 50 mg/m.sup.2, at least about
60 mg/m.sup.2, or at least about 70 mg/m.sup.2. Usually the amount
of silver will not be higher than about 1 g/m.sup.2, e.g., not
higher about 600 mg/m.sup.2, not higher than about 450 mg/m.sup.2,
not higher than about 200 mg/m.sup.2, or not higher than about 80
mg/m.sup.2 of the composite.
[0072] One or more other layers may be arranged between the
antimicrobial metal and the first layer and/or the second layer.
For example, an intermediate layer may be arranged on the surface
of the first layer (and/or the second layer) onto which the
antimicrobial metal is to be applied. The intermediate layer may
serve various purposes, e.g., to provide a higher optical density
in order to improve the aesthetic appearance (in particular, where
the amount of antimicrobial metal is relatively low) and/or to
produce a more uniform coating and/or to promote adhesion of the
antimicrobial metal, etc. The intermediate layer preferably
comprises aluminum (e.g., in the form of a thin aluminum metal film
produced by deposition from the gas phase), but any other
material(s) can be used as well as long as they are suitable for
the desired purpose(s) and, in particular, do not interfere with
the release of the antimicrobial metal and the antimicrobial
activity thereof.
[0073] In a preferred embodiment of the composite of the present
invention, the first layer of the composite is laminated to the
second layer (preferably a liquid-absorbing layer such as, e.g., a
nonwoven) by using meltable fibers under heat and pressure. Welding
(e.g., ultrasonic welding) is an example of the various other
techniques which may be employed for this purpose. In the case of
spot-welding the bond between the first layer, e.g., a mesh, and
the second layer, e.g., a liquid-absorbing nonwoven, tends to be
relatively weak, wherefore a type of bonding with a larger contact
area between these layers is preferred. Yet another non-limiting
example of the techniques for bonding the first and second layers
together is the use of adhesives. In this case, the utilized
adhesive should not significantly interfere with the release of the
antimicrobial metal (e.g., silver) or cause inconvenience to the
user.
[0074] Preferably, the first layer of the composite of the present
invention is bonded to the second layer by continuous bonding,
e.g., substantially completely (as opposed to bonding in certain
places only, like in the case of, e.g., spot-welding). Where the
first layer is laminated to the second layer by using meltable
fibers, a sufficient amount of meltable fibers should be used to
ensure sufficient resistance against delamination.
[0075] The composite of the present invention (without any
additional layers which may optionally be present, such as, e.g., a
backing layer etc.) will preferably have an area weight (as
determined according to DIN EN 29073-1) of at least about 50
g/m.sup.2, e.g., at least about 80 g/m.sup.2, and not more than
about 300 g/m.sup.2, e.g., not more than about 230 g/m.sup.2, or
not more than about 160 g/m.sup.2. Also, the composite preferably
has a thickness (as determined according to DIN EN 29073-2) which
is not lower than about 0.4 mm, e.g., not lower than about 0.5 mm,
and not higher than about 2.5 mm, e.g., not higher than about 1.4
mm. Furthermore, the composite will usually show a peeling or
delamination strength (as determined according to DIN 53357) of at
least about 0.05 N/cm, e.g., at least about 0.15 N/cm, and not
higher than about 1.5 N/cm, e.g., not higher than about 0.8 N/cm.
The minimum single value of the peeling strength (as determined
according to DIN 53357) will usually not be lower than 0.05 N/cm.
Additionally, the composite will usually show a maximum tensile
strength (as determined according to DIN EN 29073-3) of from about
10 N/cm to about 40 N/cm. Furthermore, the 24-hour release of
antimicrobial metal (e.g., silver) provided by the composite of the
present invention (as determined according to the method described
hereinbelow) preferably is at least about 0.05 mg/m.sup.2,
particularly, at least about 0.1 mg/m.sup.2, but usually it will
not be higher than about 3 mg/m.sup.2, e.g., not higher than about
2 mg/m.sup.2 of composite.
[0076] A wound covering article according to the present invention
may, by way of non-limiting example, comprise the above composite
and a cover or backing layer arranged on the second layer of the
composite (e.g., directly bonded to the second layer or to any
intermediate layer such as, e.g., a liquid-permeable layer which
may optionally be present in a composite wherein the second layer
is made of a liquid-absorbing material). The cover layer may
comprise any material that is suitable for this purpose.
Non-limiting examples of corresponding materials include a nonwoven
(e.g., composed of polyester), a polyolefin (e.g. polyethylene)
film and a combination thereof. The cover layer may carry an
adhesive on the surface which is to come into contact with the
second (or intermediate) layer and, optionally, also with the skin.
Non-limiting examples of suitable adhesives are disclosed in, e.g.,
DE 27 43 979 C3. For example, commercially available
pressure-sensitive or UV-curable adhesives based on acrylate or
rubber may be used for this purpose. Preferable is the use of
thermoplastic hot-melt adhesives based on natural and synthetic
rubbers and other synthetic polymers such as, e.g., acrylates,
methacrylates, polyurethanes, polyolefins, polyvinyl derivatives,
polyesters and silicones. These adhesives may optionally contain
additives such as, e.g., tackifying resins, softeners, stabilizers
and other auxiliary agents. Subsequent cross-linking of the
adhesive by UV or electron beam radiation may be advantageous.
[0077] Hot-melt adhesives based on block copolymers, in particular,
are distinguished by their numerous varieties. By specifically
lowering the glass transition temperature of the pressure-sensitive
adhesive through selection of the appropriate tackifier, softener,
the polymer molecule size and molecular weight distribution of the
individual components, an appropriate adhesion to the skin is
ensured also at critical locations of the human locomotive
system.
[0078] It has surprisingly been found that, for example, a wound
covering article which does not have the antimicrobial metal (e.g.,
silver) on the surface of a liquid-permeable layer which is to come
into contact with the wound (i.e., not on an external surface
thereof, but has the metal on the opposite surface of the layer, is
capable of releasing a sufficient amount of the metal to give rise
to an antimicrobial (disinfectant) effect when the article is in
contact with a wound.
[0079] It is surprising that a wound covering article (e.g., a
wound dressing) according to the present invention shows an
antimicrobial activity, as demonstrated by release tests of
dissolved silver, as well as by efficacy studies. These studies
demonstrate a marked antibacterial activity against Escherichia
coli and Pseudomonas aeruginosa and a somewhat lower activity
against Staphylococcus aureus and Enterococcus hirae, in this
order.
[0080] A composite according to the present invention is useful, in
particular, as a wound dressing or wound covering such as a
compress. Its use in skin care, e.g., as a cosmetic towelette or in
baby care is advantageous as well, particularly, because the
antimicrobial metal in elemental form does not directly contact the
skin.
[0081] A composite of the present invention in the form of, e.g., a
wound dressing or other wound covering material which comprises an
antimicrobial metal such as silver shows many advantages, including
the following: [0082] upon contact of the silver layer with a wound
fluid, silver (ions) is (are) released and exert(s) an
antimicrobial effect, [0083] there is no direct abrasion or release
of silver particles into the wound or onto the skin, which
minimizes the risk of complications in wound healing or skin care,
[0084] where a mesh, perforated film or the like is provided as a
cover layer over a textile material (as liquid-absorbing material)
fibers from the textile material are prevented from being released
into the wound and/or adhering to the wound.
[0085] Surprisingly, the structure according to the present
invention can be realized without, or at least without substantial
loss, of antimicrobial activity. In the case of silver, this
activity is observed already with a very slight coating of silver,
and a coating of preferably at least about 10 mg silver/m.sup.2 is
particularly preferred to ensure satisfactory antimicrobial
activity. More silver can also be applied, e.g., for reasons of the
manufacturing process. It has been shown, for example, that the
application of as much as about 600 mg/m.sup.2 of silver does not
harm the user.
[0086] A comparison with known silver-containing wound dressings
has shown that a dressing according to the present invention
releases an advantageously high amount of silver at the beginning
of the application. Moreover, the release rate is also sufficiently
high over an extended period after application; excessive doping
with silver is, therefore, not required, and the wound dressing
does not have to be replaced already after a short period of time.
This is of great advantage to users since they can use the dressing
for longer periods without loss of antimicrobial (disinfecting)
activity.
[0087] Another advantage of a dressing according to the present
invention is related to abrasion. Rubbing one's finger on the side
of the dressing which faces the skin reveals no abraded material,
let alone black discoloration, in contrast to known wound
dressings. This is particularly advantageous, in particular, for
aesthetic reasons, for dressings that are used without a
physician's supervision.
[0088] In addition to its use as a dressing or wound covering in
the form of, e.g., a compress, the composite according to the
present invention can also be used in other areas, e.g., for skin
care applications. For example, moistened skin may be covered or
wiped with the composite, for example in the form of a cloth. The
moisture will penetrate the cover layer into the moisture-absorbing
layer and thereby contact the metal (silver) layer. The
antimicrobial metal will be released, thereby providing the
antimicrobial effect associated with the metal. One of the
advantages of the composite of the present invention is that the
skin will not get discolored in these cosmetic uses. This is a
substantial improvement over conventionally used products such as,
e.g., baby care wipes and dressings.
[0089] Other exemplary embodiments and advantages of the present
invention may be ascertained by reviewing the present disclosure
and the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0090] The present invention is further described in the detailed
description which follows, in reference to the noted plurality of
drawings by way of non-limiting examples of exemplary embodiments
of the present invention, in which like reference numerals
represent similar parts throughout the several views of the
drawings, and wherein:
[0091] FIG. 1 shows the results of discoloration tests carried out
with various wound dressings;
[0092] FIG. 2 shows top and cross-sectional schematic views of the
general structure of an embodiment of the present invention;
[0093] FIG. 3 shows a top schematic view of an embodiment of the
present invention in the form of a bandage product; and
[0094] FIG. 4 shows a cross-sectional schematic view of an
embodiment of the present invention in the form of a bandage
product.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0095] The particulars shown herein are by way of example and for
purposes of illustrative discussion of the embodiments of the
present invention only and are presented in the cause of providing
what is believed to be the most useful and readily understood
description of the principles and conceptual aspects of the present
invention. In this regard, no attempt is made to show structural
details of the present invention in more detail than is necessary
for the fundamental understanding of the present invention, the
description taken with the drawings making apparent to those
skilled in the art how the several forms of the present invention
may be embodied in practice.
[0096] Abrasion resistance tests were used to examine abrasion
resistance. These tests were analogous to the rubbing fastness test
for dyes and prints according to DIN 54021. The subsequent
evaluation was carried out according to ISO 105-A03: 1993 with a
gray scale of from 1 to 5. 1 represents a strong, black
discoloration, and 5 represents no discoloration at all. The
results are shown in FIG. 1, wherein the tested products are
identified as follows: [0097] A: Acticoat.RTM.; grayness: 3 [0098]
B: silver-coated dressing, silver facing the skin; grayness: 2
[0099] C: dressing according to the invention, manufactured as
described below; [0100] grayness: 5
[0101] The dressing according to the present invention (FIG. 1, C)
has a grayness of 5, i.e., shows no discoloration. The comparative
products, on the other hand, show discolorations with a grayness of
2 to 3. This advantageous reduction of abrasion in the case of the
product of the invention is advantageous, especially, for aesthetic
reasons.
[0102] FIG. 2 shows top and cross-sectional schematic views of the
general structure of an embodiment of the composite according to
the present invention. A liquid-permeable layer (2) is laminated
onto a liquid-absorbing layer (1). On the side which faces layer
(1), layer (2) is coated with silver (3). In a preferred
embodiment, a layer of aluminum (4) is arranged between layer (1)
and the silver coating (3). The aluminum layer makes it easier to
coat the silver more uniformly and improves the appearance.
[0103] The composite according to the present invention is
particularly suitable for use in, or as a wound dressing for
self-adhesive bandage products, and also as an isolated wound
covering that may be additionally fastened to the wound.
[0104] FIGS. 3 and 4 show top and cross-sectional schematic views
of another embodiment of a material according to the present
invention in the form of an adhesive strip. The dressing (A) which
comprises the following layers: [0105] liquid-absorbing layer (1)
[0106] liquid-permeable layer (2) [0107] aluminum layer (4) [0108]
silver layer (3) is provided on a backing layer (5) which is coated
with an adhesive layer (6). The strip thus has a structure which is
similar to that of classic bandages. Prior to use, the adhesive
layer and the wound covering may be covered with a sealing paper
(7).
[0109] Where additional adhesion is desired, the dressing according
to the invention can be adhered to the skin by adding adhesive
around the edge as shown in FIG. 3. In this case, the dressing
according to the present invention will have a structure similar to
that of known wound bandages. Peripheral adhesion is possible as in
the case of bandages, as is adhesion on both sides as in the case
of rolled stock.
[0110] The dressing material according to the present
invention--with or without additional edge adhesive--may be placed
on a wound in the usual way, with substantially no elemental silver
coming into contact with the wound.
[0111] Once the silver-containing dressing is removed, the
antibacterial effect ceases. Usually, the skin or wound will not
have to be washed as no antiseptics and antibiotics will have to be
removed.
EXAMPLE
[0112] A commercially available polyethylene net (Delnet.RTM.,
available from Applied Extrusion Technologies, and also available
from Smith & Nephew Extruded Films Ltd. U.K.), having
triangle-shaped holes (length of longest bisector: 400-700 .mu.m)
is coated, by vapor deposition, first with aluminum and then with
silver (alternatively, a commercially available PE net that already
is coated with aluminum may be used). The area weight of the
resultant Al and Ag coated net is about 20 g/m.sup.2. The content
of Al is about 60-80 mg/m.sup.2 and the content of Ag is about
60-460 mg/m.sup.2. The coated net is laminated to a needle-punched
nonwoven (Maliviies) with the coated side facing the nonwoven. The
nonwoven is composed of about 75 weight-% of rayon (viscose) and
about 25 weight-% of polyethylene/polypropylene fibers and has an
area weight of about 120 g/m.sup.2. Lamination is carried out under
heat and pressure (by slightly melting the PE/PP fibers and
pressing the two layers together).
[0113] A material which was made as described above showed the
following properties: [0114] Area weight (DIN EN 29073-1): 125
g/m.sup.2 [0115] Thickness (DIN EN 29073-2): 0.75 mm [0116] Maximum
tensile strength (DIN EN 29073-3): 15.8 N/cm [0117]
Delamination/peeling strength (DIN 53357): 0.95 N/cm [0118] Minimum
single value of delamination/peeling strength (DIN 53357): 0.40
N/cm [0119] Liquid absorption (DIN 53923): 620 g/m.sup.2 [0120]
Release of silver (see the method described below): 0.46 mg/l after
24 h [0121] Efficacy: The antimicrobial activity against
Staphylococcus aureus, Enterococcus hirae, Escherichia coli,
Pseudomonas aeruginosa and Candida albicans was tested. It was
found that in all cases the material showed bactericidal,
bacteriostatic and/or fungicidal activity. Method of Determining
Release of Silver:
[0122] The release of silver was determined by an extraction of the
silver from a sample of the material (square with a side of 30+/-1
cm) into a phosphate-buffered saline solution (15 ml of PBS
solution) at 31.degree. C. for 24 h. The PBS solution is described
by Dulbecco (John Paul, "Zell-und Gewebekulturen", Walter de
Gruyter Publishers, 1980, p. 92). The content of Ca and Mg ions was
adjusted to wound fluid levels (0.19 g/L of
CaCl.sub.2.times.2H.sub.2O; 0.27 g/L of MgSO.sub.4.times.7
H.sub.2O; Geigy Scientific Tables, Vol. 3, Ciba-Geigy Ltd., 8th Ed.
1984, p 82). Following the extraction, the sample was carefully
removed from the solution. The aqueous phase was acidified and the
silver concentration was determined by atomic absorption
spectroscopy using an air/C.sub.2H.sub.2 flame at a wavelength of
328.1 nm.
[0123] It is noted that the foregoing examples have been provided
merely for the purpose of explanation and are in no way to be
construed as limiting of the present invention. While the present
invention has been described with reference to an exemplary
embodiment, it is understood that the words which have been used
herein are words of description and illustration, rather than words
of limitation. Changes may be made, within the purview of the
appended claims, as presently stated and as amended, without
departing from the scope and spirit of the present invention in its
aspects. Although the present invention has been described herein
with reference to particular means, materials and embodiments, the
present invention is not intended to be limited to the particulars
disclosed herein; rather, the present invention extends to all
functionally equivalent structures, methods and uses, such as are
within the scope of the appended claims.
* * * * *