Foamed silicone in wound care

Abstract

A silicone foam is described that is produced in-situ at a wound site, e.g. in a wound cavity, through a multi-component system, based on a physical foaming process, wherein the gas required to form the foam structure is provided through a blowing agent independently of the curing reaction of polyorganosiloxane components of the multi-component system. Therefore, the blowing agent is provided as a distinct entity of the multi-component system that is, in particular, not the result of any chemical reaction taking place in the multi-component system. A device for producing the foam and the corresponding negative pressure wound therapy kit are also described.

Claims

1. A multi-component system for producing a silicone foam, said system comprising: a first component comprising a first polyorganosiloxane, said first polyorganosiloxane comprising at least two silicon-bonded hydrogen atoms; a second component comprising a second polyorganosiloxane, said second polyorganosiloxane comprising at least two alkenyl- and/or alkynyl groups, and at least one hydrosilylation catalyst; said multi-component system further comprising at least one blowing agent, wherein said second polyorganosiloxane has the following general formula, representing a statistical co-polymer ##STR00004## wherein R1 is selected from monovalent or functionally substituted C4-C12 hydrocarbon group, wherein R2 is selected from monovalent or functionally substituted C1-C12 hydrocarbon group, wherein R3 to R10, independently, are selected from monovalent or functionally substituted C1-C3 hydrocarbon groups, and wherein at least one of R3 to R10 is a C2-C3 alkenyl or C2-C3 alkynyl, wherein n and m indicate the number of repeating units, and wherein the ratio between the total number of m and n is from 1:100 to 40:100.

2. The multi-component system according to claim 1, wherein RIO and R9 is a C2-C3 alkenyl or C2-C3 alkynyl, and wherein R1 and R2, independently, are selected from monovalent or functionally substituted C4-C12 hydrocarbon group.

3. The multi-component system according to claim 1, wherein R1 and R2 are independently selected from the group consisting of C5-C12 aryl, preferably phenyl or diphenyl, C4-C12 alkyl, C4-C12 alkenyl, C4-C12 alkynyl, and C4-C12 alkoxy.

4. The multi-component system according to claim 1, wherein R3 to R8 are independently selected from the group consisting of C1-C3 alkyl, C2-C3 alkenyl, C2-C3 alkynyl, and C1-C3 alkoxy, preferably methyl, ethyl, propyl, methoxy, ethoxy, propoxy group.

5. The multi-component system according to claim 1, wherein R3 to R8 are methyl, and wherein R1 and R2 are phenyl.

6. The multi-component system according to claim 1, wherein the ratio between the total number of m and n is from 2:100 to 25:100.

7. The multi-component system according to claim 1, wherein the ratio between the total number of silicon-bonded hydrogen atoms and the total number of alkenyl and/or alkynyl groups, in the multi-component system, is between 2 and 20.

8. The multi-component system according to claim 7, wherein the number average molecular weight of the first polyorganosiloxane is lower than the number average molecular weight of the second polyorganosiloxane.

9. The multi-component system according to claim 1, wherein the ratio between the total number of alkenyl and/or alkynyl groups and the total number of the silicon-bonded hydrogen atoms, in the multi-component system, is between 2 and 20.

10. The multi-component system according to claim 9, wherein the number average molecular weight of the second polyorganosiloxane is lower than the number average molecular weight of the first polyorganosiloxane.

11. The multi-component system according to claim 1, wherein said blowing agent is selected from the group consisting of propane, butane, isobutane, isobutene, isopentane, dimethylether or mixtures thereof.

12. The multi-component system according to claim 1, wherein the blowing agent is the main source for gas that leads to the formation of foam, in particular wherein the reaction between the first component and the second component essentially does not lead to the production of gas that leads to the formation of foam.

13. The multi-component system according to claim 1, wherein said first and/or said second component further comprises at least one colloidal silica or pyrogenic silica.

14. The multi-component system according to claim 1, wherein said first component further comprises said second polyorganosiloxane.

15. The multi-component system according to claim 1, wherein at least one dyestuff is added to the first and second component, respectively, wherein the at least one dyestuff for the first component is of different color compared to the at least one dyestuff of the second component.

16. A device for producing a foam comprising: the multi-component system according to claim 1; at least one means for bringing said first component and said second component into contact with each other, wherein said first component and said second component are contained separately.

17. The device according to claim 16 wherein said device comprises a first deformable container containing said first component and a second deformable container containing said second component, preferably wherein the means for bringing said first component and said second component into contact with each other is a propellant gas.

18. A silicone foam obtained from the multi-component system according to claim 1.

19. The silicone foam according to claim 18, wherein said silicone foam has a density of less than 0.7 kg/m.sup.3.

20. A negative pressure wound therapy kit comprising: a negative pressure source for providing negative pressure to a wound; a multi-component system according to claim 1 for providing a silicone foam in a wound cavity; a film dressing comprising a plastic film to be applied on said silicone foam, to cover and substantially seal the wound from surrounding environment.

21. A method of treating a wound comprising a wound cavity comprising the step of: providing a multi-component system according to claim 1; in-situ producing and curing a silicone foam within said wound cavity having an entire area such that said produced silicone foam is in physical contact with substantially the entire area of the wound cavity; providing a film dressing on a top surface of said silicone foam and on skin surrounding said wound, to thereby provide a substantially air-tight seal over the wound; providing a negative pressure source for providing negative pressure to the wound; providing a conduit configured to transmit negative pressure from said negative pressure source to said film dressing; and connecting said conduit to said negative pressure source.

22. A method of treating a wound according to claim 21, wherein the silicone foam is produced essentially with the blowing agent that is part of the multi-component system and essentially without any gas formed as a result of the reaction between said first component and said second component.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other aspects of the invention will now be shown in more detail, with reference to the appended drawings showing an exemplary embodiment of the invention, wherein:

(2) FIG. 1 is a cross-sectional view of an embodiment of a device according to the invention; and

(3) FIG. 2 is a schematic perspective view of an embodiment of a negative pressure wound therapy kit according to the invention.

DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

(4) In the following description, exemplary embodiments of the present invention are described, with reference to the accompanying drawings.

(5) FIG. 1 illustrates an exemplary embodiment of a device for producing a foam, comprising a multi-component system comprising: a first component comprising a first polyorganosiloxane comprising at least two silicon-bonded hydrogen atoms; a second component comprising a second polyorganosiloxane comprising at least two alkenyl- and/or alkynyl groups and at least one hydrosilylation catalyst; and at least one blowing agent.

(6) As illustrated in FIG. 1, the device may be realized as a spray dispenser 10 comprising a first deformable container 1 containing the first component 3 and a second deformable container 2 containing the second component 4. The first deformable container 1 and the second deformable container 2 may be realized as plastic pouches, which are gas and liquid impermeable and which have controllable opening.

(7) In some embodiments, for example as depicted in FIG. 1, the spray dispenser 10 comprises a mixing nozzle 6 and a discharge valve 7, wherein the first deformable container 1 and second deformable container 2 are connected, and sealed, to the mixing nozzle 6. The spray dispenser device 10 further comprises a propellant gas 5, as a means for bringing the first component 3 and the second component 4 in contact with each other, which propellant gas 5 is present between the first 1 and second 2 deformable containers and an interior surface 8 of the spray dispenser 10. Thus, when the spray dispenser 10 is triggered, the propellant gas 5 can facilitate an optimal mixing of the first component 3 and second component 4.

(8) Further, at least one of the first component 3 and the second component 4 comprises a blowing agent that is substantially dissolved therein. For example, the first deformable container 1 containing the first component 3 and/or the second deformable container 2 containing the second component 4 may typically be provided with the blowing agent at an elevated pressure of at least 1.5 bar, wherein the blowing agent may be selected such that its solubility in the first component 3 and/or in the second component 4 is at least 3% w/w at 20 C. The concentration of the blowing agent in the first component 3 and/or the second component 4 may advantageously be from 5 to 20% w/w, such as from 10 to 15% w/w.

(9) The blowing agent advantageously has a boiling point of less than 25 C. For example, the blowing agent may have a boiling point of less than 20 C. or less than 10 C., such as less than 5 C. or less than 0 C. In embodiments of the invention, the blowing agent may have a boiling point of between 50 to 25 C., for example between 50 C. to 10 C. such as between 40 C. to 0 C.

(10) In some embodiments, the blowing agent comprises a compound selected from the group consisting of propane, butane, isobutane, isobutene, isopentane, dimethylether or mixtures thereof. In some embodiments, the blowing agent advantageously comprises a compound that is inert in the sense that it does not react with any chemical or compound, nor does it interfere with the curing reaction between, the first component 3 and the second component 4.

(11) Thus, by (i) selecting a blowing agent that has a boiling point below the normal temperature of use, e.g. skin temperature or room temperature, that is, by means of selecting a blowing agent that is gaseous outside the spray dispenser 10; and by (ii) properly adjusting the concentration of the blowing agent in the first component 3 and/or the second component 4, in the respective pressurized deformable containers, the blowing agent may instantly provide a foam structure in the mixture of the components, i.e. upon first mixing the first component 3 and the second component 4 and applying the mixture on a surface, e.g. on a skin surface or in a wound cavity, which foam structure is then rapidly stabilized (frozen) as the first component 3 and the second component 4 cure to provide a permanent structure around the foam's cavities.

(12) In some embodiments, the viscosity of the first component 3 and the second component 4, independently, ranges from 5000 to 50000 mPa s (cP). In some embodiments, the viscosity of the first component 3 and second component 4, independently, ranges from 10000 to 30000 mPa s (cP), for example, from 15000 to 25000 mPa s (cP), such as about 20000 mPa s (cP). In some embodiments, the viscosity of the first component 3 and the second component 4 is substantially the same.

(13) By adapting the viscosity of the first component 3 and the second component 4 to be substantially the same, the mixing thereof may be further optimized as the first component 3 and the second component 4 may be released from their respective deformable containers 1, 2 at substantially the same rate.

(14) In embodiments of the invention, not shown in FIG. 1, the device may comprise a first deformable container containing the first component and a second deformable container containing the second component, wherein the device may comprise a third deformable container containing the blowing agent. In some embodiments, the device may comprise a third deformable container containing the blowing agent, and wherein the blowing agent may also be comprised in at least one of the first and second components.

(15) In embodiments of the invention, the second polyorganosiloxane has the following general formula representing a statistical copolymer:

(16) ##STR00002## wherein R1 and R2, independently, are selected from monovalent or functionally substituted C4-C12 hydrocarbon group, wherein R3 to R8, independently, are selected from monovalent or functionally substituted C1-C3 hydrocarbon group, wherein n and m indicate the number of repeating units, wherein n and m, independently, are at least one, typically greater than 5. The ratio between the total number of m and n may vary from 1:100 to 40:100.

(17) In embodiments of the invention, R1 and R2, independently, are selected from the group consisting of C5-C12 aryl, preferably phenyl or diphenyl, C4-C12 alkyl, C4-C12 alkenyl, C4-C12 alkynyl, and C4-C12 alkoxy.

(18) In embodiments of the invention, R3 to R8, independently, are selected from the group consisting of C1-C3 alkyl, C2-C3 alkenyl, C2-C3 alkynyl, and C1-C3 alkoxy, preferably methyl, ethyl, propyl, methoxy, ethoxy, propoxy group.

(19) In embodiments of the invention, the ratio between the total number of m and n is from 2:100 to 25:100.

(20) For example, in embodiments of the invention, the second polyorganosiloxane has the following formula representing a statistical copolymer

(21) ##STR00003## wherein n and m indicate the number of repeating units, wherein n and m, independently, are at least one, typically n may be from 50 to 1500, such as from 500 to 1500, and m may typically be from 5 to 150, such as from 30 to 100, and wherein the ratio between the total number of m and n preferably is from 1:100 to 40:100, for example, from 3:100 to 30:100, such as from 5:100 to 25:100.

(22) As disclosed above, the inventors have realized that in order to ensure a fast curing reaction in the multi-component system it may be advantageous that either (i) the total number of silicon-bonded hydrogen atoms in the multi-component system are in excess of the total number of alkenyl and/or alkynyl groups in the multi-component system, wherein the polyorganosiloxanes comprising the silicon-bonded hydrogen atoms, e.g. the first polyorganosiloxane, preferably have a lower average molecular weight than the polyorganosiloxanes comprising the alkenyl and/or alkynyl groups, e.g. the second polyorganosiloxane; or (ii) the total number of alkenyl and/or alkynyl groups in the multi-component system are in excess of the total number of silicon-bonded hydrogen atoms in the multi-component system, wherein the polyorganosiloxanes comprising the alkenyl and/or alkynyl groups, e.g. the second polyorganosiloxanes, preferably have a lower average molecular weight than the polyorganosiloxanes comprising the silicon-bonded hydrogen atoms, e.g. the first polyorganosiloxane.

(23) Thereby, the smaller polyorganosiloxanes comprising the functional groups in excess have a greater mobility in the reaction mixture of the multi-component system, than the larger polyorganosiloxanes comprising the functional groups in deficit, which overall enhances the reaction rate of the curing reaction.

(24) In embodiments of the invention, the number average molecular weight of the first polyorganosiloxane is less than the number average molecular weight of the second polyorganosiloxane. In embodiments of the invention, the number average molecular weight of the second polyorganosiloxane is less than the number average molecular weight of the first polyorganosiloxane. In embodiments of the invention, the first polyorganosiloxane or the second polyorganosiloxane has a number average molecular weight of 500 to 6000 g/mol, for example, 1000 to 4000 g/mol, such as about 2000 g/mol or about 3000 g/mol. In embodiments of the invention, the first polyorganosiloxane or the second polyorganosiloxane has a number average molecular weight of 10000 to 150000 g/mol, for example, 20000 to 100000 g/mol, such as about 25000 g/mol or 60000 g/mol.

(25) In embodiments of the invention, the first polyorganosiloxane has a number average molecular weight of 500 to 6000 g/mol, and the second polyorganosiloxane has a number average molecular weight of 10000 to 150000 g/mol. Alternatively, in some embodiments, the second polyorganosiloxane has a number average molecular weight of 500 to 6000 g/mol, and the first polyorganosiloxane has a number average molecular weight of 10000 to 150000 g/mol.

(26) In embodiments of the invention, the total number of silicon-bonded hydrogen atoms on each first polyorganosiloxane molecule is from 2 to 50, for example, from 5 to 30.

(27) In embodiments of the invention, the total number of alkenyl and/or alkynyl groups on each second polyorganosiloxane molecule is from 2 to 8, for example, from 2 to 6.

(28) In embodiments of the invention, the ratio between the total number of silicon-bonded hydrogen atoms and the total number of alkenyl and/or alkynyl groups, in the multi-component system, is between 2 and 20, for example, between 4 and 16 or between 6 and 10, such as 8. Alternatively, in embodiments of the invention, the ratio between the total number of alkenyl and/or alkynyl groups and the total number of the silicon-bonded hydrogen atoms, in the multi-component system, is between 2 and 20, for example, between 4 and 16 or between 6 and 10, such as 8.

(29) In addition, to further ensure a fast curing reaction, it is advantageous the multi-component system comprises at least one hydrosilylation catalyst in relatively high concentrations as specified herein.

(30) In embodiments of the invention, the at least one hydrosilylation catalyst comprises a platinum complex.

(31) In some embodiments, the at least one hydrosilylation catalyst comprises a divinyl tetramethyl disiloxane-platinum(0)-complex or a methyl vinyl cyclosiloxane-platinum(0)-complex. In some embodiments the at least one hydrosilylation catalyst further comprises a solvent comprising a vinyl-terminated polydimethyl siloxane, divinyl tetramethyl disiloxane and/or a methyl vinyl cyclosiloxane. In embodiments of the invention, the total concentration of platinum in the in the multi-component system is more than 50 ppm, for example, more than 100 ppm. In some embodiments, the total concentration of platinum in the in the multi-component system ranges from 50 to 300 ppm. In some embodiments, the total concentration of platinum in the in the multi-component system ranges from 50 to 200 ppm, for example, from 50 to 150 ppm or from 100 to 200 ppm. Thereby, a fast curing reaction rate between the first and the second polyorganosiloxane can be facilitated.

(32) In embodiments of the invention, the multi-component system or the device comprising the multi-component system is used in wound care. For example, as illustrated in FIG. 2, the multi-component system or the device comprising the multi-component system may be particularly advantageously be used in negative pressure wound therapy. In some embodiments, the multi-component system or the device comprising the multi-component system is used in wound irrigation treatment or in wound instillation treatment.

(33) FIG. 2 illustrates an embodiment of a negative pressure wound therapy kit 20 comprising a negative pressure source 21 for providing negative pressure to a wound W, and the spray dispenser device 10 comprising the multi-component system for providing a silicone foam 22 in the wound cavity W. The negative pressure wound therapy kit 20 further comprises a film dressing 23 comprising a plastic film 24 to be applied on the silicone foam 22 to cover and substantially seal the wound W from surrounding environment. Also included in the kit 20 is a conduit 25 that can be connected, as shown in FIG. 2, to the negative pressure source 21 and to the film dressing 24, thereby providing a negative pressure in and around the wound.

(34) The silicone foam 22 comprises an at least partially open pore structure wherein the density ranges from 0.1 to 0.6 kg/m.sup.3, for example from 0.2 to 0.5 kg/m.sup.3 or from 0.2 to 0.4 kg/m.sup.3, such as about 0.3 kg/m.sup.3. When the multi-component system is used in negative pressure therapy it is preferred that at least some amount of liquid is transported through the open-cells in the silicone foam produced from the multi-component system, e.g. that liquid can be transported from a surface facing the wound W to a top surface facing the film dressing 24. For example, the silicone foam may comprise at least one channel from a first external surface of the foam to a second external surface of the silicone foam, wherein the at least one channel comprises a plurality of coherent open cells. In some embodiments, the silicone foam may comprise a surface, e.g. the top surface, wherein no open-cells are present, e.g. a continuous film of cross-linked silicone. Thus, in case the silicone foam is used in negative pressure wound therapy, it may be preferred to make a small cut in the top surface of the silicone foam before or when applying the film dressing on the silicone foam, to thereby expose open-cells on the top surface, and ensure that fluid can go through the silicone foam piece and that a negative pressure can be produced in the silicone foam.

(35) The advantages of the invention have been demonstrated in the following Example.

EXAMPLES

(36) Method of Preparing a Foam Based on the Multi-Component System According to the Present Invention

(37) Materials: PLY4-7560 was purchased from NuSil Technology LLC, Catalyst 510 and Crosslinker 110 were purchased from Evonik Hanse GmbH.

(38) Preparation of two silicone mixtures: Using a mechanical rotary mixer, 908 g PLY4-7560 and 92 g Crosslinker 110 were mixed to a homogeneous mixture in a plastic jar. Using the same equipment, 1910 g PLY4-7560 and 90 g of Catalyst 510 were mixed in a second jar.

(39) Preparation of a multicomponent foam producing device: 10 g of the first mixture was transferred to a can (transfer can) and mixed with 10% isobutane. The can was subsequently pressurized using nitrogen gas. 20 g of the second mixture was transferred to a second can and mixed with 10% isobutene. The can was subsequently pressurized using nitrogen gas. Using the pressure in both transfer cans, the silicone mixtures from the cans were transferred into two separate containers in a pre-pressurized (with nitrogen gas) final container.

(40) Preparation of a foam using the multicomponent device: The final container was equipped with an actuator connected to a static mixer. By pressing the actuator the two mixtures were allowed to enter the static mixer, mix, and finally exit the multicomponent device into a jar for subsequent foaming and curing. After approx. 5 minutes, the foam was removed from the jar.

(41) Method of Preparing a Colored Foam Based on the Multi-Component System According to the Present Invention

(42) Materials: PLY4-7560, MED-4900-5 (yellow-colored first component) and MED-4900-7 (blue-colored second component) were purchased from NuSil Technology LLC. Catalyst 510 and Crosslinker 110 were purchased from Evonik Hanse GmbH.

(43) Preparation of two siloxane mixtures: Using a speed mixer, 90.8 g PLY4-7560, 9.2 g Crosslinker 110 and 2.0 g MED-4900-5 were mixed to a homogeneous yellow-colored mixture in a plastic jar. Using the same equipment, 191.0 g PLY4-7560, 9.0 g Catalyst 510 and 4.0 g MED-4900-7 were mixed to a homogeneous blue-colored mixture in a second jar.

(44) Preparation of a green-colored cured silicone material: approximately 2 g of the yellow-colored siloxane mixture and 4 g of the yellow-colored siloxane mixture, were transferred to a two-compartment syringe equipped with a plunger and static mixer to simulate a pressurized can. The plunger was pressed down manually and the two siloxane components were mixed through the static mixer and exiting the device as a homogeneous green-colored silicone mixture, which no discernible effect of the dyestuff present.

(45) Method of Measuring Density of the Silicone Foam

(46) A small piece of the foam (approx. 135 cm) was weighed (4.13 g) and placed into a 100 mL measuring cylinder. A known volume (50 mL) of spherical metallic beads (d=2 mm) were added to the measuring cylinder, completely surrounding the foam. The foam volume (15 cm.sup.3) was obtained by the subtraction V.sub.foam+particlesV.sub.particles, giving a foam density of 0.3 g/cm.sup.3.