JPH04303445A - wound dressing - Google Patents

Abstract

PURPOSE:To favorably grow new outer layer of the skin from the edge of a wound without staying of a bleeding liquid from a living body between a wound surface and a wound covering material and transient inflammatory reaction and the drying death of the wound surface by dispersing a designated amount of particles and/or fiber of hydrophilic material of a designated size in a film formed by a continuous phase of a hydrophobic material. CONSTITUTION:Either or both of granulated hydrophilic material with a particle diameter of 1000mum or less and the same material with a particle diameter of 200mum and a length of 5000mum or less are dispersed in a film formed by a continuous phase of a hydrophobic material. The quantity of hydrophilic material is 20wt. parts to 100wt. parts of hydrophobic material. The wound covering material is made by casting hydrophobic base material solution where particles or short fibers formed by hydrophilic material are dispersed on a suitable flat plate, and drying the same. As hydrophobic material, polyurethane, silicone, poly-butadienem are cited and as hydrophilic material cellulose, cellulose oxide, a cross-linking dextran and so on, are cited.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wound dressing, and more particularly to a wound dressing suitable for treating external wounds such as cuts, abrasions and burns.

0002

2. Description of the Related Art Conventionally, various wound dressings have been developed for treating skin defects caused by the above-mentioned trauma. Typical examples include bio-derived materials such as freeze-dried pig dermis, collagen non-woven fabrics, chitin non-woven fabrics, synthetic materials such as polyurethane membranes, and biological/synthetic materials such as silicone membranes/nylon fabrics/collagen composite membranes (called Bio-Blen). There are composite materials.

[0003] Bio-derived materials such as bonded dried pig dermis, collagen nonwoven fabric, chitin nonwoven fabric, etc. have the advantage of being hydrophilic and adapting to the wound surface, having excellent drainage of exudate, and adhering well to the wound surface, but the durability of the dressing material is poor. There are disadvantages such as: when the wound surface dries, it hardens to a crisp and becomes less transparent; it may be decomposed and melted by enzymes in the exudate, and the dressing may lose its function. Synthetic materials such as polyurethane membranes have excellent durability and transparency, but they have the disadvantage of poor adhesion to the wound surface and the tendency for exudate to accumulate between the wound surface and the dressing, delaying wound healing. be.

[0004] Japanese Patent Publication No. 61-37952 discloses a bandage made of a bio-synthetic composite material. Its main embodiments are silicone membrane/nylon fabric/
It is a collagen complex that forms a strong adhesion between the wound surface and the dressing material, compensating for the drawbacks of the polyurethane membrane, but the adhesion between the nylon fabric and the wound surface is too strong, causing the wound surface to deteriorate. There are disadvantages such as inhibiting epithelialization, and because the silicone membrane is essentially a hydrophobic barrier, on a wound surface with a lot of exudate, accumulation occurs between the wound surface and the dressing, making it difficult to adhere tightly.

[0005] JP-A-58-7251 discloses a composite wound dressing comprising a polytetrafluoroethylene fibril matrix and a partially occlusive film containing hydrophilic absorbent particles and coated on the surface. It has been shown that this product works well for shallow small wounds by absorbing exudate and not adhering to the wound surface. However, since this is basically a occlusive type wound dressing, in the case of deeper or larger wounds, it is possible that it cannot prevent exudate from accumulating on the wound surface and inhibits wound healing.

[0006] It is known that accumulation of exudate inhibits wound healing [W. B. Rockwell and H. P. Ehr
lick, Journal of Burn Curn
Care and Rehabilitation,
11, 93-95 (1990); “Should Bu
rnBlister Fluid BeEvacuat
Ed? As shown in [], it has been proven by a large amount of scientific data in recent years.

[0007]Also, even if the outer coating layer is changed to increase water vapor permeability in order to prevent accumulation, which is not a normal embodiment of the present invention, tissue may penetrate into the polytetrafluoroethylene fibril matrix and cause damage to the wound surface and wound covering. This may cause excessive adhesion between the wound surface and the wound surface, which may delay epithelialization of the wound surface.

[0008] The ease with which fibroblasts invade the knitted fabric layer consisting of fine fibers [Satoshi Nyu et al., Artificial Organs, 19, 128]
7-1291 (1990); “Healing-promoting highly porous artificial blood vessel - Angiogen using ultra-fine polyester fibers”
It can be easily inferred from the description of "Esis-"]. Also,
Since it is formed from a fibril matrix and fine particles, it has poor transparency, and it is virtually difficult to see through the wound surface when a wound dressing is applied, which is considered to be inconvenient in use.

[0009] JP-A-58-190446 discloses a sealed multilayer bandage consisting of an adhesive layer containing a water-dispersible hydrocolloid material, an intermediate layer of semi-open cell polymer foam, and an outer film; 1986-
185270 discloses a flexible closed-cell polyurethane foam containing a water-dispersed, water-swellable, and/or water-absorbing material;
An occlusive wound dressing is disclosed comprising a film laminated to one side of the foam and a pressure sensitive adhesive laminated to the other side of the foam.

However, since these are basically occlusive wound dressings, in the case of deeper or larger wounds, it is conceivable that they cannot prevent exudate from accumulating on the wound surface, thereby inhibiting wound healing. In addition, all of them have a multilayer structure, and it is substantially difficult to see through the wound surface with the wound dressing applied, which is considered to be inconvenient in use.

[0011] JP-A-2-147062 discloses a wound dressing material consisting of two layers of a polyurethane film with a specific molecular structure and a bio-derived material sheet, which is effective in covering full-thickness abdominal skin lesions in rats. It is stated that. However, this wound dressing is basically based on the assumption that the bio-derived material sheet will be incorporated into the living tissue, which inevitably causes an inflammatory reaction due to the decomposition and absorption of the bio-derived material sheet, which may have a negative impact on the wound surface. .

[0012] Furthermore, since the tissue invades into the bio-derived material and the adhesion between the wound dressing and the wound surface becomes stronger, epithelialization of the wound surface in shallow wounds may be delayed. Furthermore, since the water vapor permeability of the polyurethane film is high both when wet and when dry, it may lead to dry necrosis of the wound surface that is in close contact with the wound dressing.

[0013] Japanese Utility Model Application Publication No. 63-200447 discloses a wound covering material in which a chitin layer is attached to a porous polytetrafluoroethylene film. It basically consists of a porous polytetrafluoroethylene film, which has no transparency, tissue can penetrate into the porous polytetrafluoroethylene film, and create too strong an adhesion. etc. can be considered as a decision.

[0014]

[Object of the invention] The present invention prevents accumulation of exudate from the living body between the wound surface and the wound dressing material, does not cause excessive inflammatory reaction or dry necrosis of the wound surface, and furthermore, The purpose of the present invention is to provide a wound dressing material that also allows for good growth of new epidermis.

[0015]

[Structure of the Invention] The present invention provides a particulate hydrophilic substance with a particle size of 1000 μm or less and a granular hydrophilic substance with a diameter of 200 μm or less and a length of 5000 μm.
Either one or both of the fibrous hydrophilic substances of m or less,
The present invention relates to a wound dressing having a structure in which a hydrophobic substance is dispersed in a continuous phase film, and the amount of the hydrophilic substance is 20 parts by weight or more based on 100 parts by weight of the hydrophobic substance.

The above-mentioned hydrophobicity means that the water absorption rate is 2 at 37°C.
less than 0% by weight, preferably less than 5% by weight,
The above-mentioned hydrophilic property means that the water absorption rate is 20% by weight or more at 37° C. and that the material is substantially insoluble in water. If a hydrophilic substance that is substantially soluble in water at 37°C is used, when a wound dressing is applied to the wound surface, part or all of the hydrophilic substance will be eluted due to the presence of exudate. Therefore, in addition to changes in the constituent components of the membrane over time, it is necessary to consider the incorporation of eluted hydrophilic substances into the wound surface, and the wound dressing material will exhibit a different effect from that intended by the present invention. .

[0017] The wound dressing according to the present invention comprises a film consisting of a continuous phase (100 parts by weight) of a hydrophobic base material, in the form of granules with a particle size of 100 μm or less, or with a particle size of 200 μm in diameter.
Fibrous hydrophilic substance with a length of 5,000 μm or less (
20 parts by weight or more) is dispersed in the film, and is created by, for example, casting a hydrophobic base solution in which fine particles or short fibers made of a hydrophilic substance are dispersed onto a suitable flat plate and drying it. be done. It can also be produced by kneading hydrophilic fine particles or fibers with a hydrophobic polymer using a roll and then pressing the mixture.

[0018] Hydrophobic substances used in the present invention include:
It is not particularly limited as long as it satisfies the above conditions and has the strength to protect the wound surface as a base material for a wound dressing, but it is preferably one that exhibits appropriate flexibility and workability. Typical examples include polyurethane, silicone, polybutadiene, styrene-butadiene copolymer, polyisoprene, natural rubber, butyl rubber, and the like.

[0019] Hydrophilic substances used in the present invention include:
There are no particular limitations as long as the above conditions are met. Typical examples include cellulose, oxidized cellulose, cross-linked dextran, collagen, gelatin, chitin,
Examples include chitosan, agar, calcium alginate, or derivatives or mixtures thereof.

[0020]

Effects of the Invention As a result of extensive research, the present inventor has discovered that by dispersing a predetermined amount of particles and/or fibers of a hydrophilic substance of a predetermined size in a film consisting of a continuous phase of a hydrophobic substance, the hydrophilic Development of a wound dressing that exhibits non-occlusive properties when wetted due to the presence of substance particles and/or fibers, does not allow exudate from the living body to accumulate, and eliminates the aforementioned problems of conventional wound dressings. succeeded in. The present invention has been made based on this knowledge.

The above-mentioned non-occlusion property when wet means that under the condition that one side of the film is in contact with water, the water permeation rate is 5000 g/m2/m at a temperature of 35° C. and a relative humidity of 0%.
This means 24 hours or more.

[0022] In the present invention, the hydrophilic substance usually has a particle size of 1000
It is used in the form of granules with a diameter of 200 μm or less and a length of 50,000 μm or less, but if larger than this, the uniformity of the film will be difficult. The amount of the hydrophilic substance is 20 parts by weight or more based on 100 parts by weight of the hydrophobic base material, but usually 100 parts by weight of the hydrophobic base material.
The amount is preferably 20 to 400 parts by weight; if the amount is more than this, the hydrophobic substance tends to be relatively small and discontinuous, resulting in a decrease in strength. 20
If the amount is less than parts by weight, the moisture permeability in wet conditions will not be sufficient. In this wound dressing, the hydrophilic substance is normally dispersed almost uniformly over the entire surface, but if necessary, the water vapor permeation performance can be controlled by making the distribution of the hydrophilic substance uneven.

[0023] Since this wound dressing has a structure in which a hydrophilic substance is dispersed in a continuous phase of a hydrophobic base material, when wetted, the hydrophilic substance probably swells with water and the concentration of water in the film increases. The distribution changes significantly compared to when it is dry, and in membranes made of the same material and shape, the water permeability increases as the amount of hydrophilic substances in the membrane increases.

As a result, typical embodiments of the invention comply with ASTM E96-80 procedures when wet.
ure BW at 35℃ - relative humidity 0%
According to measurements at 35℃-relative humidity 0, the moisture permeation rate was
% of 5,000 g/m2/24 hr or more and is non-occlusive. At the same time, ASTM E
When measured at 40° C. and 75% relative humidity by a method according to 96-80 procedure A, the film exhibits a water vapor permeability value close to that of a film made only of a hydrophobic substrate having a similar structure. A low value leads to prevention of water and bacteria from entering the wound surface from the outside and excessive drying of the wound surface.

[0025] Since this wound dressing is basically non-occlusive, there is little risk of exudate accumulating between the wound dressing and the wound surface. , perforations or pores may be provided through the wound dressing to assist in their evacuation. This wound dressing adheres closely to the wound surface and exhibits a good wound surface protection effect when the amount of exudate is reduced, and the presence of cuts or pores does not have any adverse effect on the wound surface (see FIGS. 8 and 9 described below).

[0026] After the film is produced, crosslinks can be introduced between the polymer chains to improve the strength. An open mesh of material such as nylon fibers may be incorporated into the wound dressing to maintain mechanical strength. Providing appropriate unevenness to the surface of the present wound dressing on the wound side helps to form good adhesion between the present wound dressing and the wound surface. A suitable adhesive may also be used to facilitate fixation of the wound dressing to the wound surface. Further, after the hydrophilic substance-containing hydrophobic base film is produced, the surface of the film may be coated with a hydrophilic substance as necessary to adjust the amount of the hydrophilic substance exposed on the surface to an appropriate value.

When applying the present wound dressing to a wound surface, it is usually fixed with surgical tape, a surgical stapler, etc., and then a sterile gauze is layered on the outside to absorb exudate, and a light pressure bandage is applied. A portion of the exudate from the wound surface is absorbed by the outer gauze, so replace the outer gauze as appropriate. The hydrophilic components exposed on the wound surface side of this wound dressing interact with lymphocytes, neutrophils, macrophages, protein components, etc. in the exudate to form appropriate adhesion between this wound dressing and the wound surface. .

[0028] The high moisture vapor permeability of the present wound dressings when wet aids in the formation of a cohesive bond. This close contact is usually maintained until the epithelialization of the wound surface is completed, so that good wound management can be achieved by simply replacing the outer gauze as appropriate during that time. The water vapor permeability of this wound dressing when dry is lower than that of conventional technology that does not contain hydrophilic particles, which means that the wound dressing prevents excessive drying of the wound surface and maintains a good healing environment. help.

[0029] Furthermore, since this wound dressing basically has a structure in which fine particles are dispersed in a continuous phase of hydrophobic polymer, if the hydrophobic polymer base material itself has good transparency, its properties will change. It is partially preserved, and the state of the wound surface can be observed while the wound dressing is applied. In this sense, the fine particles contained in the present wound dressing are preferably 50 μm or less, more preferably 10 μm or less, and the thickness of the wound dressing is preferably 200 μm or less.

[0030] Since this wound dressing does not have a porous structure that allows fibroblasts to invade into the dressing, granulation may excessively invade the wound dressing and cause too strong adhesion, inhibiting wound healing. There is no. Furthermore, the dressing does not melt and the outer gauze does not stick to the wound surface, as is often the case when pork skin is used. Once epithelialization of the wound surface is completed, the wound dressing will naturally peel off.

[0031] In addition, wound dressings made of biomaterials are not normally used for deep wounds because of melting, and occlusive wound dressings are not normally used due to the risk of infection, but this wound dressing has good water vapor permeability, adhesion to the wound surface,
It can be used because of the stability of the material, and is useful in terms of protecting the wound surface until autografting.

[0032]

[Examples] Examples of the present invention will be described below.

Example 1 [Manufacturing method] Polyurethane Tec manufactured by Thermedics
offlex EG80A 0.25g, chitosan fine particles manufactured by Kimitsu Chemical Industry Co., Ltd. (average particle size 6 μm, water absorption rate 800%)
)0.15-0.30g and 5ml of tetrahydrofuran are mixed and stirred at about 60°C for 3 hours to dissolve the polyurethane. This was poured onto a glass Petri dish with an inner diameter of 9 cm, and after air-drying at room temperature for 24 hours, the film was peeled off from the Petri dish. This was vacuum dried at room temperature for 24 hours and then cut into appropriate sizes to obtain test pieces used in the following evaluations. Tecoflex EG80A 0.07 as a comparison sample
-0.50 g and 5 ml of tetrahydrofuran, a polyurethane film was prepared in the same manner and used as a test piece.

[Evaluation of water vapor permeability] (1) The diameter of the water vapor permeable part of the water vapor permeability measuring cup under conditions that the wound dressing does not come into contact with liquid water is 12 mm, and the conditions of the constant temperature and humidity chamber are 40 mm. ASTM E96-80 procedure except ℃ and 75% humidity
The water vapor permeability of each sample was measured by a method similar to A.

(2) Water vapor permeability under conditions where the wound dressing comes into contact with liquid water The diameter of the water vapor permeable part of the measuring cup is 10 mm, and the conditions of the constant temperature and humidity chamber are 35°C and 0% humidity. ASTM E96-80 pr
The water vapor permeability of each sample was measured by a method similar to Ocedure BW.

The outline of the apparatus used for the measurements (1) and (2) above is schematically shown in FIGS. 6 and 7, respectively.

In FIG. 6, the cup 14 in the constant temperature and humidity chamber 15 is
The drying material 12 is charged into the drying material 12, and the measurement sample 11 is placed on top of it.
The weight of the entire cup 14 is measured in advance. Then, the temperature inside the constant temperature and humidity chamber 15 is 40°C, and the relative humidity is 75°C.
%. After 24 hours have elapsed, the cup 14 is taken out and weighed, and the water vapor transmission rate is determined from the increase in cup weight, that is, the increase in sample weight.

In FIG. 7, the cup 14 in the constant temperature and humidity chamber 15 is
Fill with water, place the measurement sample 11 on top of it,
After measuring the weight of the entire cup, turn it upside down. Then, the inside of the constant temperature and humidity chamber 15 is maintained at a temperature of 35° C. and a relative humidity of 0%. After 24 hours have elapsed, the cup 14 is taken out and weighed, and the water vapor transmission rate is determined from the decrease in sample weight in the same manner as described above.

[Tensile strength test evaluation] JIS-7113-
A tensile strength test was conducted in accordance with the method published in 1981. The results are shown in Table 1A and Table 1B below.

[0040]

[0041]

FIGS. 1, 2, 3, 4, and 10 are samples N, respectively.
o. This is a sketch of the electron microscope structure (magnification: about 1000 times) of cross sections of Nos. 3, 4, 5, 6, and 8. In both cases, the uneven surface is the side to be adhered to the wound surface, and the flat surface is the opposite side. In each figure, the lower line segment indicates a length of 10 μm. In FIGS. 1, 2, 3, and 4, it is observed that chitosan fine particles 2 are dispersed in the continuous phase 1 of polyurethane. FIG. 10 shows the structure in a slightly oblique view of the film's fractured surface, and 3 in FIG. 10 is the film surface (the surface that appears in an oblique direction that is close to parallel).

Example 2 Gelatin powder manufactured by Nitta Gelatin Co., Ltd. (average particle size 48 μm, water absorption rate 1000%), Pharmacopoeia agar powder manufactured by Ina Foods Co., Ltd. (average particle size 59 μm, water absorption rate 300%), Kimitsu Chemical Industry Co., Ltd. Calcium alginate powder manufactured by Toyo Roshi Co., Ltd. (average particle size 39 μm, water absorption rate 200%), cellulose fiber manufactured by Toyo Roshi Co., Ltd.
300 mesh; fiber diameter 10-20 μm, length 30-250 μm, water absorption 80%), 0.25 g each individually or in total, Tecoflex EG80A 0.2
A film was prepared in the same manner as in Example 1 using 5 g and 5 ml of tetrahydrofuran. Their physical property data are shown in Table 2A and Table 2B below.

[0044]

[0045]

Example 3 Using a domestic rabbit weighing approximately 3 kg, the back was shaved and disinfected under general anesthesia with pentobarbital sodium, and 1 ml of physiological saline was injected intradermally to swell the skin and cover the surface. One split-thickness skin defect wound with a depth of approximately 0.70 mm and a diameter of approximately 15 mm was excised using a free hand dermatome.
Two locations were created. No. shown in Examples 1 and 2 above. Each of the wound dressings Nos. 3 to 13 as well as Biobrane (registered trademark U.S. Wood)
roof Laboratories Inc. made)
The wound surface was covered with adhesive tape, and the periphery of each dressing was fixed with adhesive tape, and sterile gauze and sterile absorbent cotton were placed thereon and compressed and fixed with an elastic bandage. After observing the wound macroscopically on the 7th postoperative day, the cross section of the wound was histologically observed using hematoxylin-eosin staining. The results are shown in Table-3.

[0047]

[0048] In all cases where chitosan fine powder was used, a good healing process was observed. On the other hand, in the case of polyurethane-only films, dry necrosis of the dermis on the wound surface is observed with thin films, which tends to delay the elongation of new epidermis, and thick films tend to cause exudate accumulation and wound damage. Poor adhesion of the dressing was observed, and the wound surface showed no tendency to heal.

[0049] The use of gelatin powder also showed a good healing tendency, similar to the case of fine chitosan powder. agar end,
In the case of calcium alginate powder and cellulose fibers, slight dry necrosis of the dermis was observed due to their high water vapor permeability procedure A, but the degree of dry necrosis was slight and there was no space between the wound surface and each wound dressing. Pseudoeosinophil・
A moderate amount of macrophages were exuded, forming a scab-like layer, and new epidermis was observed to grow underneath.

In the case of Biobrane, the adhesion between the wound dressing and the wound surface was remarkable, but foreign giant cells were observed around the Biobrane nylon mesh, indicating that the extension of the new epidermis was suppressed. observed.

FIG. 8 is an enlarged perspective view of a wound dressing material in which the aforementioned perforated cuts 6 are made, and FIG. 9 is an enlarged perspective view of a wound dressing material in which the same pores 7 are provided. Due to the presence of the perforated cuts 6 and pores 7, when there is a large amount of exudate from the living body, the adhesion of the wound dressing to the wound surface is improved, which is effective in protecting the wound surface.

[Brief explanation of drawings]

FIG. 1: Wound dressing sample No. of Example. This is a sketch of the electron microscope structure of a cross section of No. 3.

[Figure 2] Same sample No. This is a sketch of the electron microscopic structure of the fracture surface of No. 4.

[Figure 3] Same sample No. 5 is a sketch of the electron microscopic structure of the fracture surface of No. 5.

[Fig. 4] Same sample No. 6 is a sketch of the electron microscopic structure of the fracture surface of No. 6.

FIG. 5 is a graph showing the relationship between the amount of chitosan (hydrophilic substance) blended and water vapor permeability.

FIG. 6 is a schematic diagram schematically showing an outline of an apparatus for measuring water vapor transmission rate in a dry state.

FIG. 7 is a schematic diagram schematically showing an outline of an apparatus for measuring water vapor transmission rate in a wet state.

FIG. 8 is an enlarged partial perspective view (partially in section) of a wound dressing according to another embodiment.

FIG. 9 is an enlarged partial perspective view (partially in section) of a wound dressing according to yet another embodiment.

FIG. 10 is a sketch of an electron microscope structure of a fractured surface of a comparative wound dressing material (No. 8).

[Explanation of symbols]

1 Continuous phase of polyurethane (hydrophobic substance) 2
Chitosan (hydrophilic substance) fine particles 11 Wound dressing sample 12 Desiccant 13 Water 14 Cup 15 Constant temperature and humidity bath

Claims (1)

[Claims] Claim 1: Either or both of a granular hydrophilic substance with a particle size of 1000 μm or less and a fibrous hydrophilic substance with a diameter of 200 μm or less and a length of 5000 μm or less are dispersed in a film consisting of a continuous phase of a hydrophobic substance. It has a structure that
A wound dressing in which the amount of the hydrophilic substance is 20 parts by weight or more based on 100 parts by weight of the hydrophobic substance.