DEVICE FOR WOUND DRESSING

Abstract

A wound dressing device comprising at least one layer (2) of silk fibroin nanofibers and an absorbent component (4); the layer of fibroin nanofibers contacts the wound of the user and helps in the healing process.

Claims

1. A wound dressing device comprising: at least one layer of silk fibroin fibers, the fibroin fibers of said layer of silk fibroin fibers made of nanofibers and said layer of silk fibroin fibers having a weight in the range of 10 to 40 g/m.sup.2; and an absorbent component.

2. The wound dressing device according to claim 1, wherein the fibroin fibers of said layer of silk fibroin fibers have an average fiber diameter of less than 900 nm.

3. The wound dressing device according to claim 1, wherein said fibroin fibers have an average diameter within the range of 200 to 800 nm.

4. The wound dressing device according to claim 1, wherein the layer is an electrospun fibroin layer.

5. The wound dressing device according to claim 1, wherein said layer of silk fibroin fibers is free from drugs, active ingredients, or biocidal substances.

6. The wound dressing device according to claim 1, wherein said layer of silk fibroin fibers has a weight in the range of 25 to 35 g/m.sup.2.

7. The wound dressing device according to claim 6, wherein said layer of silk fibroin fibers has an average diameter within the range of 200 to 800 nm.

8. The wound dressing device according to claim 1, wherein said absorbent component is disposed between two said layers of silk fibroin fibers.

9. The wound dressing device according to claim 1, wherein said at least one layer of silk fibroin fibers comprises a single said layer, said absorbent component comprises an absorbent layer disposed adjacent said single said layer to form a composite layer, and said wound dressing device comprises a folded version of said composite layer.

10. The wound dressing device according to claim 1, wherein said absorbent component comprises at least one material selected from the group consisting of viscose fibers, polyester fibers, cellulose fibers, cotton fibers, foams, gel forming particles, gel forming fibers, gauze and wound dressing parts with liquid absorbing properties.

11. The wound dressing device according to claim 9, wherein said absorbent component is a mixture of viscose/polyester in a weight ratio 70/30.

12. The wound dressing device according to claim 1, wherein said absorbent component includes a biocidal substance.

13. The wound dressing device according to claim 1, further comprising an adhesion layer for adhering at least part of said wound dressing device to skin of a user.

14-19. (canceled)

20. A process for the preparation of a wound dressing device which comprising the following steps: a. pure fibroin meshes are solubilized by contact with CaCl.sub.2 and formic acid in mild stirring conditions, at room temperature; b. the viscous solution obtained in step (a) is poured on a suitable container and left to let formic acid evaporate; c. the mixture fibroin+CaCl.sub.2 of step (b) is then purified from CaCl.sub.2 to obtain a fibroin film; d. the film of step (c) is teared off and left to dry; e. the films are treated with formic acid, under mild stirring conditions and the solution of fibroin and formic acid is transferred into syringes to be electrospun.

20. A wound dressing device formed according to the process of claim 20.

21. The wound dressing device according to claim 21, wherein the wound dressing device includes an absorber layer formed of an absorber material selected from the group consisting of viscose fibers, polyester fibers, cellulose fibers, cotton fibers, foams, gel forming particles, gel forming fibers, gauze and wound dressing parts with liquid absorbing properties.

23. The wound dressing device according to claim 21, wherein the absorber material is a mixture of viscose/polyester in a weight ratio 70/30.

24. A method for treating a wound by entrapping bacteria in a device, said method comprising: providing a device comprising a fibroin layer made of nanofibers having an average fiber diameter of less than 900 nm; and applying said device to a wound.

25. The method as in claim 24, wherein said device further includes an absorbent material, the fibroin layer is an electrospun fibroin and said applying includes causing bacteria to become entrapped within said device.

26. The method as in claim 24, wherein the fibroin layer has an average diameter within the range of 400 to 700 nm, the device further includes an absorber layer and a further layer, said further laying being an adhesive or polymer layer, and wherein said applying includes said fibroin layer contacting skin of a user.

Description

[0034] The invention will now be further disclosed with reference to the following exemplary and non-limiting drawings, wherein:

[0035] FIG. 1 is a schematic cross sectional view of one embodiment of the wound dressing according to the invention;

[0036] FIGS. 2A and 2B are schematic cross sectional views of a further embodiment of the wound dressing according to the invention;

[0037] FIGS. 3A and 3B are schematic cross sectional views of variants of the embodiments of FIGS. 1 and 2 respectively;

[0038] FIGS. 4-5 are SEM images of details of the layer of fibroin nanofibers,

[0039] FIGS. 6-7-8 are SEM images of details and cross sectional view of the device of the invention.

[0040] It should be noticed that the Figures are not showing the real-life dimensions of the device and of its components with respect to a wound and with respect to each other.

[0041] Referring now to schematic FIGS. 1 to 2B of the drawings, the wound dressing 1 comprises an absorbent component 4, and a wound contacting layer 2 made of nanofibers of fibroin having the above disclosed features. The fibroin layer is in contact with wound 7; in general, a part of the fibroin layer 2, usually the peripheral portion, will contact also the skin 3 of the user.

[0042] Similarly FIG. 2A shows a wound dressing wherein the absorbent component is sandwiched between two layers of fibroin nanofibers. As it can be seen from FIG. 2B, such a device may be obtained by simply folding a device made of one fibroin layer and one absorbent layer; therefore, in this embodiment, the layer of absorbent material is folded so as to provide an absorbing layer actually made of two layers superimposed and connected together at one end.

[0043] The wound dressing 1 comprises an absorbent component 4, a wound contacting layer 2 made of nanofibers of fibroin having the above disclosed features.

[0044] The device of FIGS. 2A and 2B is a preferred device, wherein the absorbent component 4 is sandwiched between two layers 2 of fibroin nanofibers, which can be obtained by simply folding a device made of one fibroin layer and one absorbent layer, without sealing the three free edges of the device. When desired of needed, such a device allows a tailored treatment with therapeutic agents; in this case, the healthcare personnel may open, i.e. unfold, the device of FIGS. 2A and 2B, place the appropriate agent to the absorbent layer (4) and put the edges close again before applying it to the wound of the subject to be treated.

[0045] In an exemplary embodiment, the device of FIG. 2B is partially unfolded, i.e. opened, and sterile physiological solution is added to the layer 4 of absorbing material. The aim of this wet device is to provide humidity to a wound with low exudate; because the fibroin layer 2 is hydrophobic, water/humidity is slowly permeating through it both towards the wound and partly through the upper, i.e. external layer of fibroin. According to another exemplary embodiment, a medical composition may be added to the absorbent layers 2.

[0046] Viceversa, the absorbent material 4 will become humid by absorbing water from the fluids of the wound and thanks to this the absorbent layer will maintain the wound humid enough to help its healing process.

[0047] Referring now to FIGS. 3A and 3B, in the shown exemplary embodiment, the said structure of the FIGS. 1 and 2 have an additional adhesive layer or other polymer (i.e. silicone or PDMS) layer so that the wound contacting layer 2 forms an island in the adhesive layer or polymer layer 6. The adhesive or other polymer layer 6 is provided on one side of a film backing 5 bonded to the component 2.

[0048] FIG. 4 shows a scanning electron microscope image with a 1000× magnification. FIG. 5 shows a scanning electron microscope image with a 10000× magnification and a measurement analysis of the diameter of the fibers; the pictures of FIGS. 4 and 5 are taken with scanning electron microscope SEM-FEG MIRA3. The electron microscope measures the diameter with a software that is provided by the manufacturer; the software uses scale bar calibration. It can be appreciated that the average diameter value of the measured fibers of FIG. 5 is 780 nm.

[0049] FIGS. 6, 7 and 8 show scanning electron microscope images of the two layers of a device with different magnification, wherein the difference in the diameter of the fibers (fibroin vs absorbent agent made of viscose/polyester). As it can be appreciated, the fibroin fibers have an average diameter that is less than 800 nm whereas the absorbent fibers have an average diameter higher than 1 or more microns.

[0050] As mentioned, the invention provides for the use of nanofibers of silk fibroin to provide the bacteria and microorganisms with a structure where they will adhere and remain entrapped in. Thus, by removing the dressing device of the invention, the bacteria will be removed too.

[0051] The film backing and the adhesive are not necessary when the wound device is used as primary medication of a wound, and could be maintained in position on the wound e.g. by means of a traditional medical gauze or bandage or plasters or other similar fixing devices. The adhesive film backing is also not necessary, but could be replaced by another polymer film or layer for example in an embodiment of the invention which could comprise an additional layer suitable to be used together with a negative pressure apparatus.

[0052] According to another of its aspects, the invention relates to the use of the device of the invention for negative pressure wound treatment (NPWT).

[0053] The wound dressing of the invention can also be used as an absorber for bodily fluids, i.e. as part of or in a diaper for children and adults and in women absorbents. In another exemplary embodiment of the invention, the fibroin nanofibers contain, i.e. a biocidal substance or compound. The biocidal substance or compound is preferably present in the fibroin solution before the solution is electrospun; according to the type of biocidal substance, there may be a release of the biocidal substance from the nanofibers of fibroin. In a preferred embodiment, the biocidal substance is permanently bound to the fibroin; exemplary substances of this type could be permanent antimicrobial substances based on quaternary ammonium compounds.

[0054] According to another of its aspects, the invention relates to a method for treating wounds which comprises applying to a subject in need thereof a device according to the invention.

[0055] The method of the invention includes negative pressure wound treatment (NPWT).

[0056] With reference to FIGS. 2A and 2B, the method also includes the step of placing a therapeutical agent onto the absorbent (4) and putting the edges close again before applying it to the wound of the subject to be treated.

[0057] According to another of its aspects, the invention relates to a process for the preparation of a device according to the invention which comprising the following steps: [0058] a. pure fibroin meshes are solubilized by contact with CaCl.sub.2 and formic acid in mild stirring conditions, at room temperature; [0059] b. the viscous solution obtained in step (a) is poured on a suitable container and left to let formic acid evaporate; [0060] c. the mixture fibroin+CaCl.sub.2 of step (b) is then purified from CaCl.sub.2 to obtain a fibroin film; [0061] d. the film of step (c) is teared off and left to dry; [0062] e. the films are treated with formic acid, under mild stirring conditions and the solution of fibroin and formic acid is transferred into syringes to be electrospun.

[0063] Pure fibroin meshes are obtained according to known methods.

[0064] According to a preferred embodiment, the absorber layer is selected from viscose fibers, polyester fibers, cellulose fibers, cotton fibers, foams, gel forming particles, gel forming fibers, gauze and wound dressing parts with liquid absorbing properties, preferably a mixture of viscose/polyester in a weight ratio 70/30.

[0065] The invention also relates to a wound dressing device obtained or obtainable by the process above.

[0066] The preferred embodiments disclosed for the device also applied to the process of the invention.