JP2013245427A - Method for producing antibacterial regenerated silk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide regenerated silk obtained by forming fibroin with antibacterial properties.SOLUTION: The method for producing antibacterial regenerated silk includes: a water-dissolving process for dissolving fibroin obtained from silk in an aqueous solution containing a lithium salt to provide a fibroin aqueous solution; a demineralization process for removing lithium salts from the fibroin aqueous solution; a drying process for drying the fibroin aqueous solution after the demineralization process to provide dried fibroin; an organic solvent-dissolving process for dissolving the dried fibroin in a fluorine-based organic solvent to provide a fibroin organic solution; and a forming process for forming fibroin into a predetermined form by pouring the fibroin organic solution in alcohol or evaporating the fluorine-based organic solvent from the fibroin organic solution to provide an antibacterial regenerated silk.

Description

  The present invention relates to a method for producing recycled silk formed by molding fibroin.

  Conventional antibacterial fibers are provided with antibacterial properties by mixing silver ions, inorganic fine particles and the like into the material.

  Silk made from silkworm cocoons is used for clothes, cosmetics, foods, and so on. Further, since silk is a material that is known for biocompatibility, it is considered to be highly safe for the human body. Therefore, in recent years, silk has been developed as a medical-related product, such as being used as a surgical suture. Patent Documents 1 and 2 describe a technique for imparting antibacterial properties by adsorbing antibacterial metal ions such as silver ions and copper ions to silk or silk-derived fibroin.

  However, antibacterial metal ions such as silver ions mixed with antibacterial fibers and inorganic fine particles may cause metal allergy depending on the type.

In addition, although it is not an antibacterial fiber, patent documents 3-5 have the following description regarding fibroin.
Patent Document 3 describes that silk fibroin has antibacterial properties although the degree of effect is unknown.
Patent Document 4 describes that fibroin is obtained by removing sericin from sputum using an aqueous solution containing urea and mercaptoethanol.
Patent Document 5 describes that fibers are obtained by electrostatic spinning using a solution obtained by dissolving sericin and fibroin in hexafluoroisopropanol (HFIP).

JP 2003-227064 A JP 2004-18757 A JP 2005-298882 A JP 2001-163899 A JP 2007-303015 A

  An object of the present invention is to impart antibacterial properties against various fungi to a regenerated silk formed by molding fibroin by a new treatment. In addition, by combining the regenerated silk produced in accordance with the present invention with a thermosetting or thermoplastic resin, the resin molded product maintains the antibacterial and deodorant properties against various fungi possessed by the regenerated silk. Thus, the resin molded product can be expected to be used for hygiene products.

  The inventor of the present application has found that regenerated silk produced by a predetermined method using silk obtained by removing sericin from rabbits has excellent antibacterial properties (see Tables 1 to 4). However, although the mechanism by which the excellent antibacterial properties are exhibited in the regenerated silk is considered to be inherent in the treatment of the present invention, the details of the mechanism are not clear.

  The method for producing an antibacterial regenerated silk of the present invention comprises a water dissolution treatment for dissolving fibroin obtained from silk in an aqueous solution containing a lithium salt to obtain a fibroin aqueous solution, and a desalting treatment for removing the lithium salt from the fibroin aqueous solution. Drying the fibroin aqueous solution after the desalting treatment to obtain dry fibroin, dissolving the dried fibroin in a fluorine-based organic solvent to obtain a fibroin organic solution, and the fibroin organic solution. And forming the antibacterial regenerated silk obtained by forming the fibroin into a predetermined shape by evaporating the organic solvent from the fibroin organic solution.

  The aspect of each element in the present invention is exemplified below.

1. Silk Silk is not particularly limited, and examples thereof include those obtained from waste products such as silk clothing and scrap materials, and those obtained from cocoons.
The kite is not particularly limited, but may be a rabbit or a savage.

The method for obtaining silk from the cocoon cocoons is not particularly limited, but the sericin treatment is performed by dissolving and removing sericin by putting the cocoon cocoons in treated water containing urea, mercaptoethanol, and tris (hydroxymethyl) aminomethane (Tris). The method obtained by (1) can be illustrated.
Although the density | concentration of each component of the treated water used for a desericin process is not specifically limited, The density | concentration of urea can illustrate 6-10M, the density | concentration of mercaptoethanol 1-5 volume%, and the density | concentration of Tris can illustrate 20-100 mM. Moreover, although the temperature of the treated water at the time of a desericin process is not specifically limited, 70-100 degreeC can be illustrated.

2. Lithium salt The lithium salt is not particularly limited, and examples thereof include lithium thiocyanate, lithium bromide, lithium nitrate, and lithium chloride.

3. Fluorine-based organic solvent The fluorine-based organic solvent is not particularly limited, and examples thereof include hexafluoroisopropanol (HFIP), fluoroacetone (HFA), etc., and high fibroin solubility and a high-concentration fibroin organic solution can be obtained. HFIP is preferred because it is easy.

4). Water dissolution treatment The lithium salt concentration of the aqueous solution containing the lithium salt used in the water dissolution treatment is not particularly limited, but it is 1 to 1.3 times as much water as the mass ratio, that is, the lithium salt is 100 to 100 g of water. An amount of 130 g can be exemplified.
Although the quantity of the aqueous solution containing the lithium salt with respect to fibroin is not specifically limited, 40-100 times of fibroin by mass ratio, ie, the aqueous solution containing lithium salt with respect to 1g of fibroin can illustrate the quantity of 40-100g.
Although the temperature at the time of melt | dissolving fibroin, ie, a liquid temperature, is not specifically limited, 20-40 degreeC can be illustrated.

5. Desalting Treatment The desalting treatment method is not particularly limited, but dialysis, ultrafiltration, gel filtration chromatography, desalting column, and the like can be exemplified, and dialysis is preferred because they can be used properly depending on the amount of treatment.

6). Drying treatment The method of the drying treatment is not particularly limited, but a (fibrous) dried fibroin that is easily soluble in an organic solvent such as HFIP can be obtained. Thus, the desiccated fibroin aqueous solution is freeze-dried to obtain dried fibroin. The obtaining method is preferred.

7). Organic dissolution treatment The amount of the fluorine-based organic solvent relative to the dried fibroin is not particularly limited, but an amount of 6 to 20 mL can be exemplified with respect to 1 g of the dried fibroin.
Although the temperature at the time of melt | dissolving dry fibroin, ie, a liquid temperature, is not specifically limited, 30-60 degreeC can be illustrated.

8). Shape of regenerated silk The shape of regenerated silk is not particularly limited, and examples thereof include a thread shape, a film shape, and a porous shape (sponge shape).
The form of the thread-like recycled silk is not particularly limited, but may be a solid thread or a hollow thread.

9. Molding process The alcohol used for the molding process is not particularly limited, and examples thereof include methanol, ethanol, propanol, and isopropanol.

  ADVANTAGE OF THE INVENTION According to this invention, the antibacterial property with respect to various microbe can be provided to the reproduction | regeneration silk formed by shape | molding fibroin. In addition, by combining the regenerated silk produced in accordance with the present invention with a thermosetting or thermoplastic resin, the resin molded product maintains the antibacterial and deodorant properties against various fungi possessed by the regenerated silk. Thus, the resin molded product can be expected to be used for hygiene products.

  A thread-like or film-like antibacterial recycled silk was produced by the following method of the present invention.

<Desericin treatment>
9.0 mL of raw material obtained from chopping 20 rabbits was treated with 400 mL of treated water (urea concentration 8M, mercapto) in which urea, mercaptoethanol and tris (hydroxymethyl) aminomethane (Tris) were dissolved in water. The ethanol concentration was 2% by volume and the Tris concentration was 50 mM), and the mixture was stirred at 80 ° C. for 5 and a half hours to dissolve sericin contained in the raw material koji in the treated water.
Thereafter, insoluble silk (fibroin) is filtered off from the treated water, and the silk obtained by filtration is washed with distilled water, and then left to stand in a thermostatic bath at 30 ° C. for about half a day and dried. 6.7 g of silk was obtained.

<Water dissolution treatment>
6.7 g of the silk obtained above was immersed in an aqueous solution obtained by dissolving 130 g of lithium thiocyanate in 100 mL of water, and the silk was dissolved to obtain about 200 mL of an aqueous fibroin solution.

<Desalination treatment>
About 20 mL of the about 200 mL of fibroin aqueous solution obtained above is put into 10 dialysis tubes made of regenerated cellulose, and then about 50 to 65 times (volume) of distilled water is added to the fibroin aqueous solution to be treated. Each dialysis tube was immersed in the resulting container for 4 to 6 days, and lithium thiocyanate was removed by dialysis. In addition, the distilled water in each container was replaced twice during the period in which each dialysis tube was immersed in distilled water.

<Drying process>
The fibroin aqueous solution from which lithium thiocyanate was removed, obtained as described above, was divided into four equal parts, each was allowed to stand in an ethanol bath at -50 ° C. for about 1 hour and pre-frozen, and then for 1-2 days. Freeze drying was performed to obtain 6.0 g of porous dry fibroin. The obtained dry fibroin contained 100 ppm of lithium thiocyanate.

<Organic dissolution treatment>
1.76 g of the dried fibroin obtained above was placed in 17.6 mL of hexafluoroisopropanol (HFIP) and stirred at 50 ° C. for 3 days to obtain a fibroin HFIP solution.

<Thread-like recycled silk molding process>
The fibroin HFIP solution obtained above is put into a 2.5 mL syringe with a nozzle (length: 30 mm) having an inner diameter of 0.25 mm, and the fibroin HFIP solution is placed in a state where the tip of the nozzle is placed in ethanol. A filamentous regenerated silk having a diameter of about 120 μm, which was formed by discharging fibroin into a thread shape, was discharged into ethanol from the nozzle tip opening.

<Film-like recycled silk molding process>
The fibroin HFIP solution obtained above is poured into an aluminum container, and the aluminum container is placed in a fume hood and allowed to stand for 24 hours at a normal pressure of 20 to 30 ° C. to evaporate HFIP from the fibroin HFIP solution. A film-like recycled silk obtained by forming fibroin into a film was obtained.

  The antibacterial properties and deodorizing properties of the antibacterial recycled silks obtained as described above were measured.

(1) Antibacterial test of filamentous regenerated silk JIS L1902 (antibacterial test method and antibacterial effect of textile products) was applied mutatis mutandis, and the antibacterial property test of filamentous regenerated silk was performed. The results are shown in Table 2. As comparative samples, rabbits (rabbit itself), de-sericin lees (silk obtained by the de-sericin treatment), PET (polyethylene terephthalate) fibers, and nylon fibers were also tested for antibacterial properties. 1 and 2. In addition, cotton was used for the standard cloth of JIS L1902.

○ Test conditions Quantitative test: Bacterial liquid absorption method Viable count method: Pour plate culture method Test strain: Staphylococcus aureus NBRC12732
: E. coli (Escherichia coli NBRC3301)
Number of specimens: each sample 3
Sample weight: 0.2g
Inoculum volume: 0.1 mL
Test bacteria suspension: 0.05% nonionic surfactant added

○ Test operation Put a sample (0.2 g) in a vial, inoculate a sample with a bacterial solution (0.1 mL), and then tighten the cap of the vial. Then, it culture | cultivated at 37 degreeC for 18 hours. Thereafter, the bacteria were washed out from the specimen, and the number of viable bacteria was measured.

○ Measurement item The average value of the common logarithm of the number of viable bacteria and the bactericidal activity value were determined for each sample.

  As shown in Tables 1 and 2, the filamentous regenerated silk produced by the method of this example has an antibacterial activity against Staphylococcus aureus and Escherichia coli because the bactericidal activity value of Staphylococcus aureus and Escherichia coli is 0 or more. It was. On the other hand, since all the comparative samples including de-sericin sputum had bactericidal activity values of Staphylococcus aureus and Escherichia coli of less than 0, antibacterial effects against Staphylococcus aureus and Escherichia coli were not recognized.

(2) Antibacterial test of film-like recycled silk Antibacterial test of film-like recycled silk was performed according to JIS Z2801 (antibacterial processed product-antibacterial test method / antibacterial effect film adhesion method), and the results for Staphylococcus aureus were expressed. 3 shows the results for E. coli. Moreover, the antibacterial property test was done also about the nylon film as a comparative sample, and the result is shown in Table 3. A polyethylene film was used as an unprocessed test piece of JIS Z2801.

○ Test conditions Test species: Staphylococcus aureus NBRC12732
: E. coli (Escherichia coli NBRC3972)
Bacterial solution preparation solution: 1/500 NB medium Number of test pieces: Each sample 3
Test piece size: 5cm x 5cm
Test bacterial solution inoculum: 0.4 mL
Unprocessed sample: Polyethylene film

○ Test operation Place the test piece (5cm × 5cm) in the sterilized petri dish with the test surface facing up, drop the test bacterial solution (0.4mL) on the test piece, and then place the film on the dropped test bacterial solution. Cover the petri dish so that the test solution spreads over the entire film. Thereafter, the cells were cultured for 24 hours. Thereafter, the test bacteria were washed out from the test piece, the bacterial solution was completely recovered, and the number of viable bacteria was measured.

○ Measurement items The average value of the common logarithm of the number of viable bacteria and the antibacterial activity value were determined for each sample.

  As shown in Tables 3 and 4, since the film-like regenerated silk produced by the method of this example has an antibacterial activity value of Staphylococcus aureus and Escherichia coli of 2.0 or more, antibacterial activity against Staphylococcus aureus and Escherichia coli The effect was recognized. On the other hand, the nylon film has an antibacterial activity against Staphylococcus aureus because the antibacterial activity of Staphylococcus aureus is less than 2.0.

(3) Deodorizing effect test of film-like recycled silk Deodorizing effect test of film-like recycled silk was conducted, and the results are shown in Table 5.

Test Method A test piece weighed in advance was placed in the Tedlar bag 5L, and then 10 L of ammonia gas (100 ppm of ammonia, nitrogen was used as the balance gas) was placed in each Tedlar bag. The initial concentration of ammonia gas was 116 ppm.

○ Measurement item The concentration of ammonia gas in the Tedlar bag after the lapse of a predetermined time was measured by a detection tube method using a detection tube (for ammonia manufactured by GASTEC, No. 3La, No. 3L). The measurement after 24 hours was carried out from a Tedlar bag after 8 hours.

  As shown in Table 5, the concentration of ammonia gas in the Tedlar bag containing the film-like recycled silk produced by the method of the present example is lower than the concentration of ammonia gas in the blank Tedlar bag. The film-like recycled silk produced by the method of this example was recognized as having a deodorizing effect on ammonia.

From the above, the antibacterial regenerated silk produced in the examples of the present invention has antibacterial and deodorant properties against Staphylococcus aureus and Escherichia coli.
Therefore, by combining the antibacterial regenerated silk produced in the examples of the present invention with a thermosetting or thermoplastic resin, a resin molded product having antibacterial and deodorizing properties against various bacteria is obtained. The obtained resin molded product can be applied to hygiene products and the like.
In addition, the antibacterial regenerated silk produced in the examples of the present invention has antibacterial properties even when antibacterial metal ions such as silver ions and inorganic fine particles are not added. The present invention does not exclude the addition of antibacterial metal ions such as silver ions or inorganic fine particles.
In the present invention, fibroin is dissolved and used, so that various forms of antibacterial regenerated silk such as film and sponge can be obtained as well as yarn.
In the present invention, since fibroin is dissolved and used, waste cocoons that cannot be used as silk thread can be effectively used as a raw material.

In addition, this invention is not limited to the said Example, In the range which does not deviate from the meaning of invention, it can change suitably and can be actualized.
For example, in the forming process of the filamentous recycled silk, the fiber strength of the filamentous recycled silk is improved by stretching the filamentous recycled silk by 2 to 3 times in the air and stretching.

Claims (7)

Water dissolution treatment for dissolving fibroin obtained from silk in an aqueous solution containing lithium salt to obtain an aqueous fibroin solution;
A desalting treatment for removing the lithium salt from the fibroin aqueous solution;
Drying treatment for drying the fibroin aqueous solution after the desalting treatment to obtain dry fibroin;
An organic dissolution treatment in which the dried fibroin is dissolved in a fluorine-based organic solvent to obtain a fibroin organic solution;
An antibacterial regenerated silk comprising: an antibacterial regenerated silk obtained by placing the fibroin organic solution in alcohol or evaporating the organic solvent from the fibroin organic solution to obtain a regenerated antibacterial silk by forming fibroin into a predetermined shape. Production method.   The method for producing antibacterial recycled silk according to claim 1, wherein the organic solvent is hexafluoroisopropanol.   The method for producing antibacterial regenerated silk according to claim 1 or 2, wherein the lithium salt is lithium thiocyanate.   The said drying process is a process by freeze-drying, The manufacturing method of the antibacterial reproduction | regeneration silk as described in any one of Claims 1-3.   The method for producing an antibacterial regenerated silk according to any one of claims 1 to 4, wherein the desalting treatment is a treatment by dialysis.   The said predetermined shape is a thread form or a film form, The manufacturing method of the antibacterial reproduction | regeneration silk as described in any one of Claims 1-5.   7. The silk according to claim 1, wherein the silk is obtained by a de-sericin treatment in which cocoons are added to treated water containing urea, mercaptoethanol, and tris (hydroxymethyl) aminomethane to dissolve and remove sericin. A method for producing an antibacterial recycled silk according to claim 1.