PH-REGULATING WOUND DRESSING

Abstract

The present invention relates to wound dressings, more particularly for the need-based treatment of chronic and/or infected wounds, comprising a Bronsted acid and a pH-sensitive polymer, wherein the Bronsted acid is embedded in a matrix of pH-sensitive polymer or is surrounded by pH-sensitive polymer. The present invention also relates to particles containing a Bronsted acid and a pH-sensitive polymer for use in the treatment of wounds, more particularly infected wounds and/or chronic wounds.

Claims

1. A wound dressing comprising a Brnsted acid and a pH-sensitive polymer, wherein the Brnsted acid is embedded in a matrix composed of a pH-sensitive polymer or is encased in a pH-sensitive polymer.

2. The wound dressing as claimed in claim 1, wherein the Brnsted acid is contained in particles that include the Brnsted acid and the pH-sensitive polymer.

3. The wound dressing as claimed in of claim 2, wherein the particles have a diameter from 50 nm to 1000 m.

4. The wound dressing of claim 2, wherein the particles have a core that contains the Brnsted acid and that is encased in the pH-sensitive polymer.

5. The wound dressing of claim 2, wherein the particles comprise a matrix composed of the pH-sensitive polymer, in which the Brnsted acid is embedded.

6. The wound dressing of claim 1, wherein the wound dressing additionally contains a substance that is a Brnsted base corresponding to the said Brnsted acid and that is embedded together with the Brnsted acid in a matrix composed of pH-sensitive polymer or is encased in a pH-sensitive polymer.

7. The wound dressing as claimed in of claim 1 wherein the wound dressing is a wound contact layer.

8. The wound dressing as claimed in of claim 1 wherein the wound dressing is an absorbent layer.

9. The wound dressing of claim 8 wherein the Brnsted acid is contained in the absorbent layer.

10. The wound dressing of claim 7, wherein the Brnsted acid is contained in the wound contact layer.

11. The wound dressing of claim 10, wherein the Brnsted acid is contained in an amount of 0.01-100 mmol per gram in the wound contact layer which contains the Brnsted acid.

12. The wound dressing of claim 1, wherein the Brnsted acid is a substance selected from the group comprising acetic acid, citric acid, lactic acid, glyceric acid, gluconic acid, benzoic acid, aconitic acid, glutaric acid, tartaric acid, phosphoric acid, malic acid, succinic acid, glutamic acid, and combinations thereof.

13. The wound dressing of claim 1, wherein the pH-sensitive polymer is a methacrylic acid-methyl methacrylate copolymer.

14. A method of treating wounds comprising employing a particle comprising a Brnsted acid and a pH-sensitive polymer.

15. The method of claim 14, wherein the wounds are infected wounds.

16. The method of claim 15, wherein the wounds are chronic wounds.

17. The wound dressing of claim 2, wherein the particles have a diameter from 5 m to 300 m.

18. The wound dressing of claim 1, wherein the wound dressing includes a wound contact layer.

19. The wound dressing of claim 1, wherein the wound dressing includes an absorbent layer.

20. The wound dressing of claim 9, wherein the Brnsted acid is contained in an amount of 0.01-100 mmol per gram in the absorbent layer which contains the Brnsted acid.

Description

EXAMPLES

Example 1: Encased Wound Contact Layer

[0085] A polyamide knitted fabric measuring 10 cm10 cm and having a basis weight of 85 g/m.sup.2 is impregnated with 12.75 mL of a 0.3 mM solution of lactic acid. After drying completely, all the lactic acid remains in the polyamide knitted fabric. The resulting material is impregnated with a commercially available organic solution of Eudragit S 12.5 by immersing it in the solution for 10 s. The material thus impregnated is dried. After drying completely, a wound contact layer completely coated with pH-sensitive polymer remains. To obtain a sufficient layer thickness, the coating process is repeated five times.

Example 2: Encased Absorbent Layer

[0086] To achieve pH stabilization in the pH range from pH 4 to pH 4.5 and to achieve a buffer capacity of about 0.3-0.4 mmol NaOH, a polyurethane foam (Vivo MCF03, AMS) was treated per gram of foam material with 15 ml of an aqueous solution containing benzoic acid and sodium benzoate, each in a concentration of 0.04 mol/L. After impregnation, the polyurethane foam was dried completely. The product thus obtained was impregnated with a commercially available organic solution of the pH-sensitive polymer Eudragit S 12.5 (methacrylic acid-methyl methacrylate 1:2 copolymer). After drying completely, a foam coated with polyacrylate remains.

[0087] To obtain a sufficient layer thickness, the coating process is repeated one more time.

Example 3: Production of Microparticles by Spray Drying

[0088] Various lactic acid microparticles having polymer contents of 10% to 40% were produced. This was done by producing in each case 300 ml of a dispersion, which was then spray dried using a Bchi 190 Mini Spray Dryer. The compositions of the dispersions are listed in the following table:

TABLE-US-00001 Eudragit FS 30 D Lactic (polymer Number % Polymer acid present) Water MP 01 10 54.0 g 20.0 g 226.0 g (6.0 g) MP 02 20 48.0 g 40.0 g 212.0 g (12.0 g) MP 03 30 42.0 g 60.0 g 198.0 g (18.0 g) MP 04 40 36.0 g 80.0 g 184.0 g (24.0 g)

[0089] Spray drying was carried out using a Bchi 190 Mini Spray Dryer (Bchi Laboratoriums-Technik, Eislingen, Germany). A drying temperature of 95 C. was chosen. The pump delivery rate with which the dispersion was sprayed was approx. 5 ml/min. A setting of 50% was chosen as the aspirator output. The outlet air temperature was 48 C.

[0090] For further processing, the residue obtained was either suspended in water to obtain a suspension or, after renewed trituration, incorporated directly into a suitable medium in a mortar.

Example 4: Microparticles in a Wound Contact Layer

[0091] A polyamide knitted fabric measuring 10 cm10 cm and having a basis weight of 85 g/m.sup.2 is impregnated with 1.418 g of a 30% dispersion of lactic acid polymer microparticles obtained according to example 3 and having a polymer content of 10% (MP01). After drying completely, the lactic acid polymer particles remain in the polyamide knitted fabric.

Example 5: Microparticles in an Absorbent Layer

[0092] A polyurethane foam (Vivo MCF03, AMS) was impregnated per gram of foam material with 7.5 g of a 10% aqueous dispersion of lactic acid polymer particles obtained according to example 3 and having a polymer content of 40% (MP04). The foam material thus obtained may be used in a damp or completely dried state.

Example 6: Microparticles in Hydrogel

[0093] A suspension is produced from 30.0 g of hydroxyethyl cellulose, 225.2 g of lactic acid polymer particles produced according to example 3 and having a content of 20% (MP02), and 200.0 g of glycerol. In a second step, 7.0 g of Carbopol 980 NF (polyacrylate, from Lubrizol, Wickliffe, USA) is mixed with 688.0 g of Ringer's solution and stirred for two hours at room temperature. The pH is adjusted to 6.0 through the addition of approx. 75 g of sodium hydroxide solution with a concentration of 1 mol/L and stirring is continued for a further two hours. To this solution is then added very slowly, with uniform stirring, the suspension of hydroxyethyl cellulose, lactic acid polymer particles, and glycerol prepared in the first step. After the addition, stirring is continued for a further two hours. Any air incorporated can subsequently be removed by stirring under reduced pressure. A weakly acidic hydrogel is obtained that contains 2.0 mmol of lactic acid in microencapsulated form per gram. This hydrogel may be applied to a wound directly as an amorphous gel or used as a wound contact layer on an absorbent layer in a multi-ply wound dressing.