METHOD AND COMPOSITION FOR REMOVING
AN ALGINATE FROM A CUTANEOUS
SUBSTRATE
BACKGROUND OF THE INVENTION
The present invention relates generally to the removal of an alginate from a cutaneous substrate using an aqueous solution of at least one chelating agent. While chelants have been used industrially to remove alginates from substrates such as floors and vessels, their use in the field of wound management is believed to be novel.
The instant chelant compositions are of particular benefit in the field of wound management, where alginate wound dressings are commonly used. In addition to chelating agents, these compositions may also contain physiological salts and one or more EO/PO-type surfactants. The preferred compositions of this invention are non-cytotoxic.
Alginate fibres have been known for some time as 20 being useful in the preparation of surgical dressings. For example, United Kingdom Patent No. 653341 describes surgical dressings formed from fibres of calcium alginate. This reference recognizes that a failing of calcium alginate fibres is their relative insolubility in water or 25 wound exudate matter. Bonniksen in GB-A-653341 therefore proposed that a proportion of the calcium ions in calcium alginate be replaced by sodium cations, since sodium alginate was known to be more soluble than calcium alginate. The resulting process has become 30 known as "conversion" of calcium alginate to form a mixed salt alginate.
As used herein, the term "alginate" refers to any salt of alginic acid. In particular, the class of alginates includes but is not limited to, calcium, magnesium, so- 35 dium and potassium alginates, and mixtures thereof. Alginate wound dressings include any alginate-containing dressings used in the fields of human or animal wound management.
For example, EP 433354 discloses the use of mixed 40 salt alginates in the manufacture of wound dressings. In such dressings, the mixed salt alginate forms the wound contact pad. U.K. 8815132 discloses the use of mixed alginate salt fibre dressings on skin wounds. KALTOSTAT ® is a highly absorbent alginate wound dressing 45 which is commercially available from Calgon Vestal Laboratories.
If dry, alginate wound dressings are generally removed by simply soaking the dressing with saline for several minutes. Though this procedure tends to soften 50 alginate dressings, subsequent removal of the dressing may still be difficult. By contrast, the instant chelant compositions solubilize or dissolve, at least to some extent, alginates, thereby facilitating removal of alginates from cutaneous substrates to which they are af- 55 fixed. This method of removal is not known or suggested in the art.
As used herein, the term "chelating agent" refers to any compound having the ability to complex, solubilize or bind a base metal present in an alginate fiber, particu- 60 larly a calcium, magnesium, sodium or potassium ion. As such, the term chelating agent as used herein is synonymous, inter alia, with the following terms: chelant, sequestrant, sequestering agent and complexing agent. In theory, any chelating agent which solubilizes an 65 alginate can be used in the instant compositions.
As mentioned above, the instant compositions may contain one or more physiological salts and one or more
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surfactants in addition to the chelating agent. While copending and commonly assigned application U.S. patent application Ser. No. 446,276 discloses the use of aqueous compositions comprising physiological salts and EO/PO block copolymers in wound management, the presence of chelating agents is not disclosed. Exemplary of such compositions is the product SAFCLENS ® which is commercially available from Calgon Vestal Laboratories.
Also, U.S. Pat. No. 29,909 to Kurtz discloses a method of cleansing wounds which utilizes aqueous detergent solutions of ethylene oxide (EO)/propylen oxide (PO) block copolymers. The block copolymers of Kurtz are commercially available as PLURONIC® Polyols from BASF Kurtz discloses that his designated EO/PO polymers do not impair the ability of a wound being treated to resist infection. The claimed Kurtz wound cleansing compositions consist of an aqueous detergent solution of at least about 10% of an EO/PO block copolymer having an EO/PO ratio of at least 3:1 and a molecular weight of from about 5,000 to about 15,000.
A wound cleanser known as SHUR CLENS®, which is commercially available from Calgon-Vestal Laboratories, represents a commercial embodiment of a wound cleansing composition disclosed by Kurtz.
DESCRIPTION OF THE FIGURES
FIGS. 1-6 photographically demonstrate the impact of a chelant composition on alginate pads. More particularly, FIG. 1 shows an untreated alginate pad. FIGS. 2-6 show alginate pads solubilized in accordance with the "chelation score" rating system of the instant examples.
SUMMARY OF THE INVENTION
In general terms, the instant invention relates to aqueous chelant compositions and to the use thereof in wound management to remove alginate dressings from cutaneous substrates. Thus, in its broadest sense, the present invention involves contacting a wet or dry alginate which is affixed to a cutaneous substrate with a chelant solution, thereby dissolving or solubilizing at least some portion of said alginate into the chelant solution and facilitating removal of the alginate from the cutaneous substrate to which it is affixed.
In the instant method, an effective amount of an aqueous chelant composition is applied by any convenient means to a wet or dry alginate wound dressing which is adhering to a cutaneous surface, such as human or animal skin, nail or wound tissue. As used herein, the term "effective amount" refers to that amount of a chelant composition necessary to solubilize a given alginate to the desired extent. Virtually any amount of a chelating solution will begin to solubilize and soften an alginate dressing. Thus, upon contact with one of the instant compositions, the alginate is partially or completely dissolved or solubilized, thereby facilitating removal. In a preferred embodiment, the alginate dressing is completely solubilized and flushed away, leaving a substantially clean cutaneous substrate.
In a more preferred embodiment of the instant invention, a non-cytotoxic alginate removal composition is used. Thus the instant invention also relates to the use of an effective amount for the above described purpose of a non-cytotoxic aqueous composition comprising: a) at least about 0.1%, by weight, of a non-cytotoxic chelat3
ing agent; b) optionally about 0.001 to about 2.0%, by weight, of a physiological salt; c) optionally, about 0.1 to about 40%, by weight, of a non-cytotoxic, non-ionic EO/PO-type surfactant; and d) the balance water; for the purpose of solubilizing, softening, facilitating the 5 removal of and/or cleansing an alginate wound dressing from a human or animal cutaneous substrate in a noncytotoxic way. Such compositions can generally be applied to an alginate dressing covering skin or wound tissue without causing substantial damage to the cellular 10 tissue underlying the dressing. These preferred noncytotoxic compositions are also claimed herein.
It is noteworthy that various components of wound management solutions may be toxic in a wound cleansing sense (that is, cytotoxic) even though they would be 15 considered non-toxic by other standards of measurement, for instance, oral toxicity, eye irritation, and skin sensitivity. Thus, while a number of components used in wound management compositions, such as detergents, may be classified as non-toxic on the basis of various 20 methodologies, they may unfortunately prove to be toxic in a wound healing sense in that they are cytotoxic.
Most commercial wound cleansers are intended for use as cleansing or irrigating solutions with minimal or 25 short term exposure to tissues. Wound cleansers usually contain anionic or amphoteric surfactants in low concentrations to provide enhanced cleaning. However, these cleansers generally lyse or kill the tissue cells in in-vitro cell cultures, usually within fifteen minutes, and 30 they generally do not effectively solubilize alginates. Though normal saline is commonly used as an irrigation fluid in the field of wound management, it has limited cleansing or solubilizing action relative to alginates. The preferred chelating compositions of this invention 35 differ in that they solubilize alginates and can remain in contact with wounds for extended periods of time without causing substantial cytotoxicity. As used herein the term "non-toxic" and "non-cytotoxic" refers to components of alginate solubilizing compositions which do not 40 cause substantial cytotoxicity as determined by the "Cytotoxicity Assay Protocol" described herein. Thus the preferred chelating agents of this invention are substantially non-cytotoxic, particularly in combination with at least one physiological salt. 45
DETAILED DESCRIPTION OF THE
INVENTION
In general terms, the instant invention is directed to a method for the removal of an alginate from a cutaneous 50 substrate, wherein said method comprises A) contacting said alginate with an effective amount of a composition which comprises:
(a) at least about 0.1 weight %, based on the weight of said composition, of at least one chelating agent; and 55
(b) the balance water; thereby solubilizing, to some extent, said alginate and facilitating its removal from said cutaneous substrate; and B) removing said alginate from said cutaneous substrate. Physiological salts and/or ethylene oxide/propylene oxide block 60 copolymers can also be used in these compositions. The instant invention is also directed to a method for
softening and/or solubilizing an alginate wound dressing which comprises contacting said dressing with an effective amount of one of the above-described chelant 65 compositions.
More particularly, the instant invention is directed to an improved method for the removal of an alginate
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dressing from wound, skin or cellular human or animal tissue, wherein the improvement comprises contacting said alginate with an effective amount of one of the above described compositions, thereby solubilizing said alginate to some extent and facilitating its removal from the tissue covered by said dressing. Preferably, the alginate is completely solubilized and the previously covered surface is then rinsed or flushed with said composition or with a conventional rinsing agent such as saline to cleanse and/or irrigate the underlying tissue. Alternatively, if the dressing is not completely solubilized, the remaining, softened dressing is removed by conventional means.
The instant invention is also directed to compositions comprising:
(a) at least about 0.1%, based on total composition weight, of a chelant selected from the group consisting of:
(i) organic acids selected from the group consisting of citric acid, acetic acid, ethylenediamine tetracetic acid, nitrilotriacetic acid, malonic acid tartaric acid, N-hydroxyethyl-ethylene diaminetriacetic acid, diethylenetriamine pentaacetic acid, trans-1,2, cyclohexamine diamine tetracetic acid, gluconic acid and salts thereof;
(ii) polyphosphates; and
(iii) anionic vinyl addition polymers containing at least about 30%, by weight, carboxylate functionality;
(b) about 0.001 to about 2.0%, based on total composition weight, of a physiological salt;
(c) optionally, an effective amount of a nonionic, water soluble EO/PO block copolymer; and
(d) the balance water. The instant invention is further directed to a method
for removing alginates from cutaneous substrates in a non-cytotoxic manner by the use of preferred chelant compositions which have been found to be substantially non-cytotoxic. These compositions comprise: a) at least about 0.1%, based on the weight of said composition, of at least one non-cytotoxic chelating agent; b) optionally, about 0.001 to about 2.0%, based on the weight of said composition, of at least one physiological salt; c) optionally, about 0.1 to about 40%, based on the weight of said composition, of at least one non-cytotoxic ethylenoxide/propylene oxide-type surfactant polymer; and d) the balance water. A non-cytotoxic method for removing alginate wound dressings from cutaneous substrates using these non-cytotoxic compositions is also claimed.
Generally speaking, the solubilizing/alginate removal compositions described herein may be prepared by simply dissolving at least one chelant in water as component (a). The chelant can be present in an amount of from about 0.1 weight % of said composition up to its solubility limit. Deionized (DI) or distilled water is the preferred solvent.
In theory, any chelant which solubilizes a counter ion found in an alginate wound dressing can be used. Such chelants include, but are not limited to a) organic acids selected from the group consisting of citric acid, acetic acid, ethylenediamine tetracetic acid (EDTA), nitrilotriacetic acid (NTA), malonic acid, tartaric acid, Nhydroxyethyl-ethylene diaminetriacetic acid (HEEDTA), diethylenetriamine pentaacetic acid, trans1,2, cyclohexamine diamine tetraacetic acid, gluconic acid and salts thereof, especially sodium salts; b) chelating polyphosphates; and c) polymers selected from the group consisting of water-soluble anionic vinyl addition
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