JP2012080916A - Wound dressing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wound dressing that is high in biocompatibility and water retentivity and has high strength.SOLUTION: The wound dressing uses a silk fibroin porous material. The porous material has a porous layer and a film layer that has no pores on only one side of the porous layer.

Description

  The present invention relates to a wound dressing, and particularly relates to a wound dressing having high strength, high affinity for skin, and high water retention.

As a method of treating skin wounds such as burns, pressure sores, cuts, abrasions, etc., after applying a therapeutic agent to the wound surface, coat it with gauze, etc., and fix it with adhesive dressing film etc. or tape etc. A method has been used. In this method, the gauze absorbs the exudate and removes the exudate from the wound surface, thereby drying and healing the wound.
On the other hand, in recent years, wet therapy has been used to heal wounds by holding the exudate on the wound surface with a sponge or the like and actively utilizing the components contained in the exudate. This method of treatment requires a material with the characteristics that it can hold the exudate well so as not to dry the wound surface.

The wound dressing material for wet therapy includes synthetic polymers such as silicone resin porous bodies and polyurethane porous bodies, and natural polymer gels and porous bodies such as hyaluronic acid, collagen, alginic acid, and carboxymethylcellulose. Has been used. However, synthetic polymers have problems such as low affinity for skin and low water retention.
On the other hand, natural polymers have high affinity for the skin, but have problems such as low strength. For this reason, it has been necessary to ensure the strength of natural polymers by wrapping them with a cross-linked product of a cross-linking agent, use of a strength reinforcing material, gauze, or the like.
However, when a crosslinking agent is used, there is a concern that the remaining crosslinking agent may adversely affect the skin (see Patent Documents 1 and 2). In addition, when a strength reinforcing material is used, there is a concern that the structure becomes complicated or a part of the wound dressing material remains on the wound surface when peeled off (see Patent Documents 3 and 4). Furthermore, when the strength is ensured by covering with gauze or the like, it is a conventional covering material such as gauze that touches the wound surface, and a gel or porous body with high biocompatibility and high water retention is wounded. There was a problem that sufficient effects could not be exhibited because the surface was not touched.

  By the way, among natural polymers, silk has a high biocompatibility and has been conventionally used for sutures and the like, and is known to have high safety. Silk is formed from sericin and fibroin protein, and various processing methods have been proposed. For example, hydrogels using silk fibroin have been proposed (Patent Documents 5 and 6). However, when used as a wound dressing, there is a problem that the strength is weak.

JP 2002-233542 A JP 2009-148392 A Japanese Patent Application Laid-Open No. 11-319068 Japanese Patent Application Laid-Open No. 2002-200110 Japanese Patent No. 3412012 Japanese Patent Publication No. 6-94518

  An object of the present invention is to provide a high-strength wound dressing material having high biocompatibility and water retention.

As a result of intensive studies, the present inventors have found that a silk fibroin porous material is suitable as the material, and have completed the present invention.
That is, the present invention
(1) A wound dressing material using a silk fibroin porous material, wherein the porous material has a porous layer and a film layer having no pores only on one surface of the porous layer. Wound dressing,
(2) The wound dressing according to (1) above, wherein the porous body has a tensile strength of 75 to 400 kPa, and (3) the porous body includes a bactericidal agent, an antibiotic and a physiologically active substance. The wound dressing according to the above (1) or (2), impregnated or coated with at least one selected from the above;
Is to provide.

  The wound dressing material of the present invention is high in strength and easy to handle, and because of its high biocompatibility, it is gentle to the skin, has high water retention, and can efficiently retain exudate, It is very effective when treating with wet therapy.

2 is a scanning electron micrograph of a cross section of a porous body produced in Example 1. FIG. 2 is a scanning electron micrograph of a cross section of a porous body produced in Example 2. FIG. 4 is a scanning electron micrograph of a cross section of a porous body produced in Example 3. FIG. 4 is a scanning electron micrograph of a cross section of a porous body produced in Example 4. FIG. 6 is a scanning electron micrograph of the cross section of the porous body produced in Example 5. FIG. 6 is a scanning electron micrograph of a cross section of a porous body produced in Example 6. FIG. 6 is a scanning electron micrograph of the cross section of the porous body produced in Example 7. FIG. 6 is a scanning electron micrograph of the cross section of the porous body produced in Example 8. FIG. 6 is a scanning electron micrograph of the cross section of the porous body produced in Example 9. 4 is a scanning electron micrograph of the cross section of the porous body produced in Example 10. FIG. 2 is a scanning electron micrograph of a cross section of a porous body produced in Example 11. FIG. 4 is a scanning electron micrograph of a cross section of a porous body produced in Example 12. FIG. 2 is a scanning electron micrograph of a cross section of a porous body produced in Comparative Example 1. 4 is a scanning electron micrograph of a cross section of a porous body produced in Comparative Example 2. 4 is a scanning electron micrograph of a cross section of a porous body produced in Comparative Example 3. 6 is a scanning electron micrograph of a cross section of a porous body produced in Comparative Example 4. 6 is a scanning electron micrograph of a cross section of a porous body produced in Comparative Example 5. 6 is a scanning electron micrograph of a cross section of a porous body produced in Comparative Example 6. 6 is a scanning electron micrograph of a cross section of a porous body produced in Comparative Example 7. 6 is a scanning electron micrograph of a cross section of a porous body produced in Comparative Example 8. 6 is a scanning electron micrograph of a cross section of a porous body produced in Comparative Example 9. 4 is a scanning electron micrograph of a cross section of a porous body produced in Comparative Example 10. 6 is a scanning electron micrograph of a cross section of a porous body produced in Comparative Example 11. 6 is a scanning electron micrograph of a cross section of a porous body produced in Comparative Example 12.

The wound dressing of the present invention is characterized by using a silk fibroin porous material.
Here, the silk fibroin porous body means a porous body containing silk fibroin, preferably having an average pore diameter of 10 to 300 μm.

  The tensile strength of the silk fibroin porous material is preferably 75 kPa to 400 kPa. If it is 75 kPa or more, there is sufficient strength, the handling as a wound dressing is easy, and the remaining of the wound dressing on the skin is reduced. On the other hand, if it is 400 kPa or less, the adhesiveness to skin is maintained. From the above viewpoint, the tensile strength is more preferably 80 kPa to 300 kPa, and further preferably 90 kPa to 200 kPa.

The wound dressing of the present invention preferably has a high water retention rate that retains absorbed water. Since the water retention rate is high, the absorbed exudate does not flow out. More specifically, the water retention rate is preferably 85 to 100%. If the water retention rate is 85% or more, the exudate is retained and the leaked liquid rarely flows out. From the above points, the water retention of the silk fibroin porous material is more preferably 87 to 100%, and still more preferably 90 to 100%.
(Calculation method of water retention rate)
The water retention rate was measured as follows. The porous body is molded to 60 × 30 × 20 mm, used as a measurement sample, and the weight of the sample sufficiently immersed in pure water is measured (Wc). The glass plate (MSA coated micro slide glass made by Matsunami Glass, 76 × 52 mm) whose surface was sufficiently dipped in pure water and wetted with pure water was tilted at 45 degrees and placed on top of it. The surface (60 × 30 mm surface) is placed face down, and the lengthwise direction is placed up and down, and allowed to stand for 10 minutes. Thereafter, the weight of the sample is measured (Wd).
Water retention rate (%) = 100− (Wc−Wd) × 100 / (Wc)

The water absorption rate of the porous layer is preferably 0.1 to 1000 μl / s, more preferably 1 to 100 μl / s, and still more preferably 20 to 30 μl / s. When the water absorption rate is 0.1 μl / s or more, the exudate is quickly absorbed and is less likely to leak out of the wound dressing. When the water absorption rate is 1000 μl / s or less, the exudate is prevented from being excessively absorbed by the wound dressing, and the wet state of the wound part can be maintained. It is preferable that the evaporation rate is 0.01~0.2g / m ² · s, more preferably from 0.03~0.15g / m ² · s, more preferably 0.06 to 0 .1 g / m ² · s. If the evaporation rate is 0.01 or more, the leakage can be continuously maintained in a state that the wound dressing can absorb. If the evaporation rate is 0.2 g / m ² · s or less, the wound surface can be efficiently kept wet when performing wet therapy. Here, the water absorption speed and the evaporation speed are values obtained as follows. When the water absorption rate and evaporation rate of the porous layer are within the above ranges, the effect of the present invention is good.

(Calculation method of water absorption rate)
100 μl of pure water was dropped on the silk fibroin porous material (porous layer), and the time until absorption was measured. The water absorption rate is a value calculated from the following equation using the measured time. The measurement was performed 5 times, and the average value was taken as the water absorption rate.
Water absorption rate (μl / s) = pure amount of pure water / time required for water absorption (evaporation rate calculation method)
Silk fibroin porous material (porous layer) is immersed in pure water for 48 hours and completely absorbed, and then on a wire mesh in a constant temperature and humidity chamber set at a temperature of 40 ° C. and a relative humidity of 50%. The weight was measured every 1 minute until 10 minutes passed, and every 2 minutes after 10 minutes, and the change was regarded as a change in the evaporation amount of water. The evaporation rate is a value calculated from the following equation from the change in the evaporation amount from 1 minute to 30 minutes after standing.
Evaporation rate (g / m ² · s) = (Change in evaporation) / Porous material surface area

The wound dressing of the present invention is preferably in the form of a sheet, and the size and shape of the sheet can be arbitrarily set according to the wound surface. Moreover, also about the thickness of a sheet | seat, arbitrary thickness can be set according to the depth of a wound, and the quantity of exudate. The whole sheet can be a porous body.
Moreover, the silk fibroin porous body in the present invention is characterized by comprising a porous layer and a film layer having no pores on one or both sides thereof.

The film layer having no pores is a layer having substantially no pores, and is a layer having no pores or having very few pores as compared with the porous layer. By having such a film layer, the speed at which a liquid such as exudate moves through the pores and the speed at which it evaporates or diffuses are slowed down, so that the liquid permeability is lowered.
The film layer preferably has pores with an area ratio of 10% or less on the surface, and the porous layer preferably has a surface with pores with an area ratio of 50 to 98%. The film layer preferably has 20 pores / mm ² or less (more preferably 10 / mm ² or less) pores having a pore diameter of 5 μm or more. Here, the area ratio of pores on the surface, the number of pores and the pore diameter were measured by subjecting a scanning electron micrograph to image processing using image analysis software ImageJ (manufactured by National Institutes of Health). It is.
The water absorption rate of the film layer is preferably 0.1 to 3.5 μl / s, more preferably 1.5 to 3.5 μl / s, and still more preferably 2 to 3.5 μl / s. It is.
Furthermore, the evaporation rate of the film layer is preferably 0.03~0.07g / m ² · s, more preferably from 0.03~0.06g / m ² · s, more preferably 0 0.03 to 0.05 g / m ² · s. When the water absorption rate and the evaporation rate are within the above ranges, the effect of the present invention is good.

As described above, the wound dressing material of the present invention is constituted by a silk fibroin porous body having a porous layer and a film layer having no pores only on one surface thereof. As the usage method, it is preferable that the porous layer is in contact with the wound surface and the film layer is provided on the opposite surface opposite to the wound surface. This is because when such a wound dressing is applied to wet therapy, exudate from the wound surface can be absorbed and retained, and the effect of suppressing evaporation and diffusion of the exudate can be obtained.
Furthermore, the function which accelerates | stimulates healing of a wound can be given by including a chemical | medical agent in a porous layer. For example, healing can be promoted by impregnating or applying a bactericidal agent, antibiotics, physiologically active substance, or the like to the porous layer. These drugs can be used alone or in combination of two or more.
In addition, the number of pores of the film layer can be controlled, and a film layer having a small amount of pores can be formed as necessary.
On the other hand, since the film layer has very few pores, the surface is smooth. Therefore, by using the film layer as the wound surface side, it is possible to give a function of preventing adhesion and to control the liquid permeability of the film layer to control the drug release rate.

The wound dressing of the present invention can be in a form in which a sheet-like silk fibroin porous body is fixed with a dressing film, a bandage, an adhesive tape or the like.
Moreover, since the silk fibroin porous body becomes hard and brittle by drying, it is also a preferable aspect to include a moisturizing agent. As the humectant, polyvinyl pyrrolidone, polyvinyl alcohol, polyethylene glycol, glycerin and the like can be used. In such an embodiment, it is preferable to keep the wound dressing of the present invention in a hermetically sealed state so as to prevent drying in a state where the amount of moisture is maintained until just before use.

Next, the manufacturing method of a silk fibroin porous body is demonstrated.
The silk fibroin porous material used in the present invention can be produced by adding a specific additive to a silk fibroin aqueous solution, freezing the aqueous solution, and then thawing it.
The silk fibroin used here may be any silk fibroin as long as it is produced from silkworms such as rabbits, wild silkworms, and tengu. In the production of the silk fibroin porous material in the present invention, it is used as a silk fibroin aqueous solution, but silk fibroin has poor solubility and is difficult to dissolve directly in water. As a method for obtaining a silk fibroin aqueous solution, any known method may be used, but a method in which silk fibroin is dissolved in a high concentration lithium bromide aqueous solution, followed by desalting by dialysis and concentration by air drying is simple.
In the method for producing a silk fibroin porous body, the concentration of silk fibroin is preferably 0.1 to 40% by mass and preferably 0.5 to 20% by mass in a silk fibroin solution to which an aliphatic carboxylic acid is added. It is more preferable, and it is still more preferable that it is 1.0-12 mass%. By setting it within this range, a porous body having sufficient strength can be efficiently produced.

  Examples of the additive include aliphatic carboxylic acids and amino acids. Although there is no restriction | limiting in particular as an additive, A water-soluble thing is preferable and the thing with the high solubility to water is more preferable. Moreover, as an aliphatic carboxylic acid used in manufacture of a silk fibroin porous body, that whose pKa is 5.0 or less is preferable, the thing of 3.0-5.0 is more preferable, and 3.5-5. Even more preferred is zero.

  As the aliphatic carboxylic acid, for example, a saturated or unsaturated monocarboxylic acid having 1 to 6 carbon atoms, dicarboxylic acid, or tricarboxylic acid can be preferably used. For example, formic acid, acetic acid, propionic acid, butyric acid, succinic acid, Examples include lactic acid, acrylic acid, 2-butenoic acid, and 3-butenoic acid. These aliphatic carboxylic acids can be used alone or in combination of two or more.

The amino acid is not particularly limited, and examples thereof include monoaminocarboxylic acids such as valine, leucine, isoleucine, glycine, alanine, serine, threonine, and methionine, and monoaminodicarboxylic acids (acidic amino acids) such as aspartic acid and glutamic acid. Examples include aliphatic amino acids, aromatic amino acids such as phenylalanine, and amino acids having a heterocyclic ring such as hydroxyproline. Among these, acidic amino acids and oxyamino acids such as hydroxyproline, serine, and threonine are preferable from the viewpoint of easy shape adjustment. . From the same viewpoint, monoaminocarboxylic acid is more preferable among acidic amino acids, aspartic acid and glutamic acid are particularly preferable, and hydroxyproline is more preferable among oxyamino acids. These amino acids can be used alone or in combination of two or more.
In addition, there are L-type and D-type optical isomers of amino acids, but when L-type and D-type are used, there is no difference in the resulting porous material, so which amino acid is used. Also good.

  The amount of the water-soluble additive added to the silk fibroin aqueous solution is preferably 0.01 to 18% by mass, more preferably 0.1 to 5.0% by mass, and 0.5 to 4.0. More preferably, it is mass%. By setting within this range, a porous body having sufficient strength can be produced. Further, if the silk fibroin solution having an additive added to the silk fibroin aqueous solution is 18.0% by mass or less, the silk fibroin porous body having a stable and uniform structure is difficult to gel when the solution is allowed to stand. can get. Moreover, it is preferable that it is 1-500 mass% with respect to fibroin, as for the compounding quantity of an amino acid, it is more preferable that it is 5-50 mass%, and it is further more preferable that it is 10-30 mass%.

Next, a silk fibroin porous body is produced by pouring the added silk fibroin aqueous solution to which the above additives are added into a mold or a container, freezing it in a low-temperature thermostatic bath, and then thawing it. The freezing temperature is not particularly limited as long as the silk fibroin solution containing the additive is frozen, but is preferably about −10 to −30 ° C. Further, the freezing time is preferably 4 hours or more at a predetermined freezing temperature so that it can be sufficiently frozen and kept in a frozen state for a certain time.
As a method of freezing, the silk fibroin solution may be frozen to a freezing temperature all at once, but once it is kept at about −5 ° C. for about 2 hours to be in a supercooled state and then lowered to the freezing temperature. Freezing is preferable for obtaining a porous body having high mechanical strength. The structure and strength of the porous body can be controlled to some extent by adjusting the time taken from −5 ° C. to the freezing temperature.
Thereafter, the silk fibroin porous material is obtained by thawing the frozen silk fibroin solution. The melting method is not particularly limited, and examples include natural melting and a method of holding in a thermostatic bath.

  The obtained porous body contains additives, but depending on the application, if it is necessary to remove the additives, the additives can be removed from the porous body by an appropriate method. . For example, the simplest method is to remove the additive by immersing the porous body in pure water. Or it is possible to remove an additive and a water | moisture content simultaneously by freeze-drying a porous body.

  The silk fibroin porous body has a sponge-like porous structure. Normally, this porous body contains water unless it is removed by lyophilization or the like, and is a rigid structure in a water-containing state. In addition, a dried silk fibroin porous material can be obtained by freeze-drying the porous material.

  The silk fibroin porous material can be formed into a shape suitable for the purpose, such as a film shape, a block shape, a tubular shape, a spherical shape, and the like by appropriately selecting a mold and a container for producing the porous material. There are no restrictions on the shape or container of the silk fibroin solution as long as it does not flow out. The material used is a material with high thermal conductivity such as iron, stainless steel, aluminum, gold, silver, or copper. It is preferable from the viewpoint of obtaining a silk fibroin porous body having a uniform structure. In addition, the thickness of the mold or the wall of the container is preferably 0.5 mm or more from the viewpoint of its function and deformation due to expansion during freezing, etc., and is easy to handle and efficient in cooling. More preferably, the thickness is 1 to 3 mm.

Moreover, the mold | type and container used here can provide a sheet | seat in the inner wall surface which contact | connects the silk fibroin solution inside for the purpose of controlling the structure and thickness of the said film layer.
As the sheet, a sheet made of a fluororesin such as polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP) or tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), or Preferable examples include release-treated sheets made of polyethylene terephthalate (PET) or polypropylene (PP). When these sheets are used, a smooth film layer with few pores can be obtained. About adoption of these sheets, what is necessary is just to select suitably according to the use of a porous body.
In addition, it is preferable to use a sheet having a thickness of 1 mm or less that hardly inhibits heat conduction.

  This silk fibroin porous body is obtained through a cutting process subsequent to the melting step described above. Further, in the sheet shape suitable as the wound dressing of the present invention, a sheet or a sheet such as a Teflon sheet is provided only on one surface, and a filter or paper is provided on the inner wall surface of the other surface. A porous body having a film layer can also be obtained.

  EXAMPLES The present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

Example 1
For silk fibroin aqueous solution, fibroin powder (KB Selen, trade name: “Fibroin IM”) is dissolved in 9M lithium bromide aqueous solution, insoluble matter is removed by centrifugation, and dialysis is repeated against ultrapure water. Was obtained by The obtained silk fibroin aqueous solution was air-dried in a dialysis tube and concentrated. A formic acid aqueous solution was added to this concentrated liquid to prepare a silk fibroin solution having a silk fibroin concentration of 5 mass% and a formic acid concentration of 2 mass%.
This silk fibroin solution was poured into a mold (inside size; 80 mm × 40 mm × 4 mm) made of an aluminum plate, and was frozen and stored in a low-temperature thermostatic bath (NCB-3300 manufactured by EYELA).
For freezing, the low-temperature thermostat was cooled to -5 ° C in advance, and a mold containing the silk fibroin solution was put into the low-temperature thermostat and held for 2 hours, and then cooled to -20 ° C and held for 5 hours. The frozen sample was returned to room temperature by natural thawing, then removed from the mold, immersed in ultrapure water, and the used formic acid was removed by exchanging the ultrapure water twice a day for 3 days. Further, the four film layers that were in contact with the side surfaces of the mold were removed by cutting, and cut at the porous layer portion to obtain a silk fibroin porous body having a film layer only on one surface of the porous layer. It was.

(Measuring method of mechanical properties)
The mechanical properties of the obtained silk fibroin porous material were evaluated using INSTRON Micro Tester Model 5548. A test piece of 40 mm × 4 mm × 4 mm was cut out from the produced silk fibroin porous material, and the maximum breaking strength (tensile strength) and the maximum strain (elongation) when the test piece was pulled at 2 mm / min were measured. In addition, the elastic modulus was obtained from the slope when the strength and strain were graphed. The results are shown in Table 1. In addition, the measurement result produced the test piece of 5 points | pieces from the produced porous body, and also cut out the test piece of 5 points | pieces from the porous body produced on the different day, and measured the average value which measured about those 10 points | pieces Show.

  Moreover, the structure of the obtained silk fibroin porous body was observed using a scanning electron microscope. The scanning electron microscope was measured using a Philips XL30-FEG in a low vacuum non-deposition mode and an acceleration voltage of 10 kV. The structure of the silk fibroin porous body was not the surface of the porous body, but the inside exposed by cutting the porous body. A scanning electron micrograph of the cross section of the obtained porous body is shown in FIG.

Examples 2-12 and Comparative Examples 1-11
In Example 1, a silk fibroin porous material was obtained in the same manner as in Example 1 except that the additives described in Tables 1 to 3 were used instead of formic acid. The evaluation results of the mechanical properties, water retention, water absorption rate and evaporation rate are shown in Tables 1-3. Moreover, the scanning electron micrographs of the cross section of the obtained porous body are shown in FIGS.
The water retention rate, water absorption rate and evaporation rate were measured as described above.

Examples 13-14
In Example 1, a silk fibroin porous material was obtained in the same manner as in Example 1 except that the types of materials described in Table 1 were used. The measurement results of the water absorption rate are shown in Table 2.

Comparative Example 12
In Example 8 of Patent Document 6, an acetic acid solution is added to a silk fibroin aqueous solution to precipitate a gel, and the resulting gel is lyophilized to obtain a porous material. In the follow-up test as described, no gel was produced, but a gel-like material and a porous material were obtained under the following conditions.
First, 130 mL of a pH 2.65 acetic acid solution was added to 50 mL of a 5% fibroin aqueous solution (pH 3.0 at this stage), and the resulting solution was allowed to stand at 5 ° C. for 40 hours to form a gel. The obtained gel was centrifuged and the supernatant was removed. After freezing at −30 ° C. for 3 hours and freeze-drying for 50 hours, a porous body was obtained. Table 1 shows the results of evaluating the mechanical properties of the porous body. Moreover, the scanning electron micrograph of the cross section of the obtained porous body is shown in FIG.

Comparative Example 13
Using a commercially available polyurethane sponge (manufactured by Sumitomo 3M), the sample was cut into measurement samples (60 mm × 30 mm × 20 mm), the water retention was measured, and the results are shown in Table 1.

[Material of mold]
A: Aluminum plate (with Teflon sheet)
B: Mirror finish acrylic board (without Teflon sheet)
C: Mirror finish polystyrene plate (without Teflon sheet)

From the results shown in Tables 1 to 3, the tensile strength of the silk fibroin porous material of Examples 1 to 12 using an aliphatic carboxylic acid or an amino acid is methanol, which is a water-soluble organic solvent used in Patent Document 4. , Ethanol, isopropanol, butanol, t-butanol, glycerol, DMSO, DMF, pyridine, acetonitrile, and acetone, which are larger than the tensile strength of the silk fibroin porous material of any of Comparative Examples 1 to 11. Moreover, the silk fibroin porous body of Examples 1-12 has a large maximum strain (elongation). Furthermore, the porous body produced in Examples 1-12 showed high tensile strength when compared with Comparative Example 12.
Moreover, it turns out that the porous layer which comprises the silk fibroin porous body produced in Example 1 has a comparatively thin wall and several tens micrometer pore from FIG. About the cross section (FIGS. 2-12) of the silk fibroin porous body produced in Examples 2-12, the substantially same scanning electron micrograph was obtained.
In addition, although the cross section (FIGS. 13-23) of the silk fibroin porous body of a comparative example had the thing with the same porous structure, and the layered structure, the correlation with those structures and mechanical characteristics is I was not able to admit. In Comparative Example 12, a clear porous structure could not be confirmed.
Moreover, the water retention of the silk fibroin porous material produced in Examples 2, 5, 6 and 11 is substantially the same as the water retention of the porous material produced in Comparative Example 2, and is in the range of 98% to 99%. I found out. In addition, the porous body produced in Comparative Example 12 was very brittle, and the water retention rate could not be calculated.

Examples 15-17
A human patch test (skin sensitization patch test) was conducted as part of a non-clinical test on the safety of silk fibroin porous materials. The skin sensitization patch test is to determine whether silk fibroin porous body induces irritation or allergic contact dermatitis on human skin.
The sheet used was the same as in Example 1 except that the inner size of the mold made of an aluminum plate was 264 mm × 205 mm × 1 mm thick, and the additives were formic acid to L-aspartic acid (Example 15), lactic acid (Example 16). ) And succinic acid (Example 17), except that it was obtained in the same manner as in Example 1. Each of these silk fibroin porous material sheets was cut into 10 mm × 10 mm × 1 mm thicknesses for use in the test, thereby preparing patches.
The test was conducted with 50 healthy Japanese women aged 18 to 65 at the start of the test. A 10 mm × 10 mm size patch used for the test was fixed to the back with a 20 mm × 20 mm hypoallergenic tape. Moreover, each patch was fixed at least 15 mm apart. For comparison, a 10 mm × 10 mm non-woven cotton fabric was fixed with a 20 mm × 20 mm hypoallergenic tape. In the test, the patch was removed 48 hours after attaching the patch, and the skin reaction was observed. Furthermore, a patch was attached to the same place, and observation was performed after 48 hours. A total of 9 times of pasting and observation were repeated. Also, two weeks later, patching at the same place and observation were repeated 4 times every 48 hours.
As a result, during the test, in Examples 15 and 16, the two subjects showed very mild erythema once, but the erythema also disappeared during the test, resulting in sheet-like silk fibroin porous The mass was found to be very hypoallergenic and not allergic.
Moreover, in Example 17, one test subject showed very mild erythema once during the test, but the result was that erythema also disappeared during the test. As a result, the sheet-like silk fibroin porous material was It was found to be very hypoallergenic and not allergic.

Example 18
A silk fibroin porous material was produced in the same manner as in Example 6 except that the size of the mold made of the aluminum plate was 130 mm × 80 mm × 12 mm (inside size).
As part of a non-clinical study on the safety of silk fibroin porous material, a primary skin irritation test and a skin sensitization test were conducted. This study is based on the “Standards for the Reliability of Application Materials” (Regulation No. 43 of the Pharmaceutical Affairs Law). Regarding the “Concept” (Pharmaceutical Proposal No. 0213001 dated February 13, 2003) and “Reference Materials on the Basic Concept of Biological Safety Testing” (Medical Device Examination No. 36, March 19, 2003) went.

(Skin primary irritation test)
The silk fibroin porous material produced in Example 18 was cut into a size of 5 mm × 5 mm × 5 mm to obtain a test piece (fibroin porous material comprising only a porous layer).
Next, a physiological saline solution and a sesame oil solution extract of silk fibroin porous material were applied to rabbits and examined for local irritation (tissue damage and inflammation-inducing properties). Specifically, physiological saline or sesame extract is added to the above test piece cut out from the silk fibroin porous material produced in Example 18, and extracted in an autoclave at 120 ° C. for 1 hour. Liquid. Moreover, only the extraction solvent (physiological saline solution or sesame oil solution) was processed under the same conditions to obtain a target solution. For administration, 6 male rabbits were used per solvent, and 0.5 mL each of the test solution and the target solution was applied to the intact skin and scratched skin on the back, respectively.
In the test solution obtained by physiological saline extraction, very slight or slight erythema was observed in 3 of 6 cases from 1 hour after administration. This erythema was also found in the physiological saline solution, which was the target solution, and was equivalent to the target solution. The primary irritancy index was 0.3, and was judged to be “negligible irritation”.
In the sesame oil extract, 4 out of 6 cases showed very mild erythema from 1 hour after administration. This erythema was also found in the sesame oil solution, which was the target solution, and was equivalent to the target solution. The primary irritation index was 0.1, which was determined to be “ignorable irritation”.

(Skin sensitization test)
With respect to the methanol extract of silk fibroin porous material produced in Example 18, the presence or absence of sensitization to guinea pig skin was examined using the Maximization Test method.
Before the skin sensitization test, the extraction rate was calculated using acetone and methanol in order to determine an appropriate extraction solvent. As a result, since methanol showed a higher extraction rate than acetone, the extraction solvent used for the skin sensitization test was methanol.
To the above test piece cut out from the silk fibroin porous material produced in Example 18, 10 mL of methanol was added and extracted using a constant temperature immersion culture machine at room temperature. The extraction was performed for 24 hours or more. As a control group, a negative control group sensitized with olive oil and a positive control group sensitized with 1-chloro-2,4-dinitrobenzene were provided. Each control group had 5 animals.
In both the test solution administration group and the negative control group, as a result of inducing with 6.25, 12.5, 25, 50, 100% solution of the extract and acetone, at any observation period of 24, 48 and 72 hours after induction No skin reaction was seen.
On the other hand, in the positive control group, an obvious positive reaction was observed 24, 48 and 72 hours after the induction in all 5 cases due to the induction of 0.1% 1-chloro-2,4-dinitrobenzene.
From this test result, it was determined that the silk fibroin porous material produced according to Example 18 did not contain a substance showing skin sensitization.
Thus, the silk fibroin porous material produced according to Example 18 has high safety due to “a negligible skin irritation” and “no substance showing skin sensitization”. It was confirmed that it can be suitably used as a wound dressing material.

  According to the present invention, there is provided a wound dressing material that has high strength, is easy to handle, has high biocompatibility, is gentle to the skin, has high water retention, and can efficiently retain exudate. Can do. Since the wound dressing of the present invention has the characteristics as described above, it is particularly effective when the wound is treated with wet therapy.

Claims (3)

  A wound dressing material using a silk fibroin porous material, wherein the porous material has a porous layer and a film layer having no pores only on one surface of the porous layer. Wood.   The wound dressing according to claim 1, wherein the porous body has a tensile strength of 75 to 400 kPa.   The wound dressing according to claim 1 or 2, wherein the porous body is impregnated or coated with at least one selected from the group consisting of bactericides, antibiotics and physiologically active substances.