JP3049250B2 - Silk fibroin powder as wound dressing and its production method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powdery wound dressing for covering a skin defect such as a wound or a burn and promoting the healing thereof.

[0002]

2. Description of the Related Art Conventionally, when a relatively large area of skin has been lost due to a wound, a burn or the like, the skin of an animal such as a pig is immediately covered therewith. The treatment was to implant another part of the skin there.

[0003] However, animal skin is not always compatible with human skin, and has the disadvantage of high cost. Also, a wound dressing called Dioactive CGF has recently been developed, but it is unlikely that the new skin that is forming under the wound dressing will be peeled off.
It is said that the rate of new skin formation under the dressing is lower than that of pig skin. These wound dressings are planar in the form of a film or cloth. Since the wound portion is not always flat, any wound dressing material can be used as long as the wound dressing is in powder form. However, amorphous silk powder has been produced by a method such as freeze-drying an aqueous silk solution. In this method, the fine ice made the fibroin porous during the freeze-drying process, so that the apparent density was low and it was difficult to treat as a wound treatment.

[0004]

DISCLOSURE OF THE INVENTION The present invention crushes an amorphous fibroin film to provide relatively good compatibility with human beings, and to cope with various forms of skin defects due to being a powder. Provided is a powdery wound dressing material which can be easily manufactured at a low cost because it is easy and has a high apparent density, and a method for manufacturing the same.

[0005]

Means for Solving the Problems A method for producing a powdery wound dressing according to the present invention for solving the above problems is characterized by comprising the following steps. a) Refining silk fiber. b) Dissolve the scoured silk fibers in an acid or neutral salt solution. c) The low molecular weight substance is removed from the solution by dialysis to obtain an aqueous fibroin solution. When the silk fiber is dissolved in an acid, the solution is dialyzed after neutralization with an alkali. d) Remove undissolved substances from the aqueous fibroin solution. e) A film-like fibroin is obtained by spreading the aqueous fibroin solution on a plate or attaching it to the roll surface to remove water. f) The fibrin in the form of a film is ground to obtain an amorphous fibroin powder as a wound dressing.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION By scouring in the step a), sericin and the like constituting the outer layer of silk fiber are removed, and an inner layer of fibroin remains. Step b) is a step for dissolving the fibroin. The solubility of fibroin can be increased by adding an alcohol to the calcium chloride solution. The dialysis in the step c) is a step in which the fibroin solution is brought into contact with water through a dialysis membrane, and low molecular substances such as salts, calcium chloride and alcohol in the fibroin solution are transferred to the water. In step d), undissolved substances are removed by a method such as filtration or centrifugation to obtain an aqueous fibroin solution. The step e) is a step of forming a thin layer by spreading the aqueous solution of fibroin on a horizontal plane or attaching the fibroin aqueous solution to the roll surface, and removing water from the thin layer by various methods to obtain a film. Various methods such as heat drying, blast dehydration, cooling drying, and ultrasonic irradiation can be used for removing water. In step f), the film-like fibroin thus obtained is mechanically pulverized to obtain a powdery amorphous wound dressing.

[0007]

EXAMPLE A method for producing a wound dressing according to an example of the present invention will be described. First, the silk fiber is scoured to remove the sericin on the surface. Next, a solution is prepared by mixing calcium chloride, ethyl alcohol and water in a molar ratio of calcium chloride: ethyl alcohol: water = 1: 2: 8. The overall weight is 50
When it is set to 0 g, the weight of each component is as follows. Calcium chloride: ethyl alcohol: water = 160 g: 132.5
g: 207.5g

[0008] Heat is generated by mixing water and calcium chloride. When mixed in the above ratio, the temperature of the solution is about 80 ° C.
Rise to the extent. When scoured silk fiber (composed of fibroin) is put therein and stirred, the silk fiber dissolves. When about 50 g of silk fiber is added to 500 g of the above solution, about 3
The entire amount dissolves in about 0 minutes. The dissolving time can be shortened by cutting the silk fiber to an appropriate length in advance and shortening the silk fiber. By changing the amount of fiber, the dissolution time and the dissolution concentration can be changed.

Next, the solution is filtered to remove the residue, thereby obtaining a fibroin solution. The fibroin solution is placed in a bag formed of a dialysis membrane, and the bag is placed in pure water, whereby calcium chloride and ethyl alcohol in the fibroin solution are discharged into the pure water. As the dialysis membrane bag, for example, a dialysis membrane manufactured by Sanko Junyaku Co., Ltd. can be used. Change to pure water every few hours to perform such dialysis.
By repeating about 10 to 30 times, calcium chloride is almost completely removed from the fibroin solution. In addition, in order to confirm that low molecular substances such as calcium chloride have been sufficiently removed, silver nitrate is added to water after dialysis for about several hours, and it is determined that it does not become cloudy.

Thereafter, the fibroin solution is taken out of the dialysis bag and spread on a flat plate of metal, plastic or the like. Then, moisture is removed by blowing lightly on the surface with a fan (that is, to such an extent that the surface is not wavy) to obtain a film. It should be noted that a method of drying by cooling to about -4 to -5 ° C may be employed. In this dehydration step, if the dehydration rate is too slow, fibroin will crystallize. The crystallized fibroin is not suitable as a wound dressing material because it is difficult to dissolve in water. Therefore, the drying of the aqueous fibroin solution must not be too long.

In the above embodiment, ethyl alcohol was previously mixed in the solution for dissolving the silk fibers, but the silk fibers were not mixed in the solution but only calcium chloride or other neutral salt and water. Heating also slightly changes the dissolution time, but it is possible to dissolve the silk fibers. The resulting fibroin film can be ground to a powder. At the time of pulverization, when the water content of the film is set to 20% or less, preferably about 10% or less, pulverization becomes easy. The grinding machine can be a commonly used physical grinding machine.

The apparent density of the obtained powder is about 0.4 g / cm ³
Met. The fibroin powder obtained by freeze-drying the aqueous fibroin solution is about 0.1 g / cm ³ or less, compared with the crystalline silk fine powder (JP-A-7-31417) of about 0.1 to 0.2 g / cm ^3. Due to the high apparent density, it is easy to spray on the skin defect. The particle size of the powder is about 100 μm, but the higher the apparent density than the size of the particle size, the easier it is to handle as a powdery wound dressing. When this powder is immersed in water, about 20% or more of it is an amorphous fibroin powder that dissolves in water.

[0013]

By coating the wound dressing material of the present invention on skin wounds, burns, etc., it is possible to prevent drying in those parts, prevent external contamination, and prevent irritation to nerve endings. Relieves pain and promotes healing. The skin defect is not necessarily flat, but has various forms. In order to apply it, the powder form is easier to use than the film form. Further, unlike the conventional animal skin, the present coating material does not need to be finally removed, but is gradually dissolved by an exudate from a wound or the like and is absorbed into the body or discharged by healing. Therefore, there is no pain at the time of removal and there is no need for replacement. Furthermore, since the present covering material is composed only of animal proteins, it has good adaptability to wounds and the like, and there is no problem if it is absorbed into the body.

Table 1 shows that the skin of the nude mouse was peeled to the dermis, and the powder according to the present invention and, as a control, Duoactive CGF (medical device approval number 0837), which had already been approved as a medical device as a wound dressing. ) Shows the results of observing the healing effect using the control as a control. The powdered wound dressing comprising the silk fibroin according to the present invention has obtained better results than the control, and it is clear that it functions well as a wound dressing.

[Table 1]

Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) A61L 15/16-15/64

Claims (4)

(57) [Claims] 1. A method for producing a powdery wound dressing, comprising the following steps: a) Refining silk fiber. b) Dissolve the scoured silk fibers in an acid or neutral salt solution. c) The low molecular weight substance is removed from the solution by dialysis to obtain an aqueous fibroin solution. When the silk fiber is dissolved in an acid, the solution is dialyzed after neutralization with an alkali. d) Remove undissolved substances from the aqueous fibroin solution. e) A film-like fibroin is obtained by spreading the aqueous fibroin solution on a plate or attaching it to the roll surface to remove water. f) The fibrin in the form of a film is ground to obtain an amorphous fibroin powder as a wound dressing. 2. The method for producing a wound dressing according to claim 1, wherein an alcohol is added to the neutral salt solution in the step b). 3. A powder wound dressing produced by the method according to claim 1. 4. An amorphous powdery wound dressing comprising a powder mainly composed of silk fibroin and having an apparent density of 0.1 g / cm ³ or more.