Gel containing bagworm silk and method for producing same

Abstract

To provide a new application technology for bagworm silk.　Provided is a gel containing bagworm silk and water.

Description

[Technical field]

[0001] The present invention relates to a gel containing bagworm silk and a method for producing the same. [Background technology]

[0002] Silk from bagworms, a general term for the larvae of moths belonging to the Psychidae family of the Lepidoptera order, has mechanical properties superior to silkworm silk and spider silk. For example, the elastic modulus of bagworm silk from the brown bagworm moth (Eumeta minuscula) is 3.5 times that of silkworm silk and 2.5 times that of spider silk from the orb spider (Nephila clavata), boasting extremely high strength (Non-Patent Documents 1 and 2).

[0003] Bagworms also have advantages over silkworms in terms of rearing. For example, silkworms are generally mulberry (genus Morus) species, and feed only on fresh leaves of mulberry trees such as M. bombycis, M. alba, and M. ihou, so the rearing area and rearing time depend on the supply area of ​​mulberry leaves and the period when the leaves open. On the other hand, bagworms are polyphagous and have low specificity for food leaves, so they can feed on the leaves of many different tree species. Therefore, food leaves are easy to obtain and they can be reared in any area. Also, depending on the species, evergreen tree leaves can be used as food leaves, so unlike mulberry trees, which are deciduous trees, food leaves can be supplied throughout the year. Furthermore, bagworms are smaller in size than silkworms, so they require the same or less space for rearing as silkworms, making it easy to rear them in large numbers. Therefore, rearing costs can be significantly reduced compared to silkworms.

[0004] Bagworms also have advantages over silkworms in terms of productivity. For example, silkworms only spin large amounts of silk when spinning their cocoons, and all larvae spin cocoons at the same time. This causes the problem of overlapping silk harvesting periods and concentrating the work period. On the other hand, bagworms spin silk repeatedly throughout the larval stage when building nests and moving. This has the advantage that the work period can be dispersed by artificially adjusting the silk harvesting period.

[0005] As described above, bagworm silk has properties that exceed those of conventional animal fibers, and has many advantages in terms of production, so it is expected to be an environmentally friendly alternative to silk (Non-Patent Document 2). For example, its application to fiber-reinforced composite materials in combination with other polymers has been reported (Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2019-44117 A [Non-patent literature]

[0007] [Non-Patent Document 1] Nature communications(2019)10:1469 [Non-Patent Document 2] Adhesion Technology Vol.39, No.4(2020):14-17 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the only application technology for bagworm silk that has been used up until now has been to utilize the fibrous properties of bagworm silk. Therefore, an object of the present invention is to provide a new application technology for bagworm silk. [Means for solving the problem]

[0009] The inventors therefore investigated ways to change bagworm silk into a form other than that of fibers and discovered, quite unexpectedly, that a hydrated gel (bagworm silk hydrated gel) could be easily formed by heating and then cooling a dispersion or aqueous solution containing bagworm silk and adjusting the water content as necessary; the resulting hydrated gel was highly stable and moldable, and could be used in a variety of technical fields, thus completing the present invention.

[0010] That is, the present invention provides the following inventions [1] to [6]. [1] A gel containing (i) bagworm silk and (ii) water (hereinafter, sometimes abbreviated as bagworm silk hydrous gel). [2] The bagworm silk hydrate gel described in [1], having a water content of 80% by mass or more and 99.99% by mass or less of the total amount of the gel. [3] The bagworm silk hydrous gel described in [1] or [2] further contains one or more components selected from gel-forming polymers, sugars, sugar alcohols, alcohols, polyhydric alcohols, water-soluble polymers and basic substances. [4] The bagworm silk hydrogel described in [1], wherein the bagworm silk is spun by the giant bagworm moth (Eumeta japonica), the brown bagworm moth (Eumeta minuscula), or the Japanese bagworm moth (Nipponopsyche fuscescens). [5] Foods, medicines, cosmetics, biomaterials, cushioning materials, elastic materials, fishing equipment, medical equipment, industrial materials, and sanitary materials containing the bagworm silk hydrous gel described in any one of [1] to [4]. [6] A method for producing a bagworm silk hydrous gel described in any of [1] to [3], characterized by heating an aqueous solution containing bagworm silk to 50°C or higher and then cooling it. Effect of the Invention

[0011] The bagworm silk hydrate gel of the present invention is a hydrate gel formed from bagworm silk, which has extremely high elasticity and strength, and water molecules, and its strength can also be changed.It can be used in a wide range of fields, including food, pharmaceuticals, cosmetics, biomaterials, cushioning materials, elastic materials, fishing equipment, medical equipment, industrial materials, and sanitary materials. [Brief description of the drawings]

[0012] [Figure 1] FIG. 13 shows the results of evaluation of the surface smoothness, shape stability, and appearance of the bagworm silk hydrogel of the present invention obtained in Example 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention relates to a bagworm silk hydrous gel, and one embodiment of the present invention is a bagworm silk hydrous gel containing (i) bagworm silk and (ii) water.

[0014] In this specification, gel refers to a solid colloid of a liquid dispersion medium. Because it is solid, it does not flow like gas or liquid. Therefore, a gel is one that has thixotropy, which means that it shows fluidity when subjected to shear stress and loses fluidity when stationary. In this specification, the hydrogel is a colloid in which the dispersion medium is water, and is in a solid state. More specifically, it is a state in which a network-like polymer has taken up a large amount of water. Bagworm silk hydrated gel is a gel in which bagworm silk has absorbed a large amount of water.

[0015] The main component of the hydrogel of the present invention is bagworm silk, which is a thread derived from bagworms, a general term for the larvae of moths belonging to the family Psychidae in the order Lepidoptera. More specifically, it is a protein-based thread spun by bagworm larvae.

[0016] The Psychidae family includes genera such as Acanthopsyche, Anatolopsyche, Bacotia, Bambalina, Canephora, Chalioides, Dahlica, Diplodoma, Eumeta, Eumasia, Kozhantshikovia, Mahasena, Nipponopsyche, Paranarychia, Proutia, Psyche, Pteroma, Siederia, Striglocyrbasia, Taleporia, Theriodopteryx, and Trigonodoma, and the bagworm referred to in this specification may be a species belonging to any of the genuses. Specific examples of bagworm species include Eumeta japonica, Eumeta minuscula, and Nipponopsyche fuscescens. The larvae may be at any stage from the first stage to the final stage. However, if the purpose is to obtain thicker and longer bagworm silk, large bagworms are preferable. For example, if it is the same species, the more mature larvae are preferred, and if it is male and female, the larger the female, the more preferred. Also, within the Psychia family, the larger the species, the more preferred. Therefore, the giant silk moth and the brown silk moth are suitable species for bagworms.

[0017] As used herein, "silk thread" refers to thread derived from insects, which is a protein-based thread spun by insect larvae and adults for the purposes of nesting, moving, anchoring, spinning cocoons, capturing food, etc. When simply referring to silk thread in this specification, it refers to bagworm silk thread unless otherwise specified.

[0018] Bagworm silk herein includes single fibers, spun fibers and aggregate fibers. A "single fiber" is the smallest unit filament that constitutes fiber components, and is also called a monofilament. Single fibers are mainly composed of fibroin-like proteins. Bagworm silk is naturally spun as difilaments and does not usually exist as single fibers. However, by going through a refining process, adhesive substances can be removed and single fibers can be obtained.

[0019] "Spun fiber" refers to silk threads in the state they are spun by bagworms. Bagworm spun fibers are composed of difilaments, each consisting of two single fibers. This form is based on the fact that two single fibers are ejected from the spinnerets, located on the left and right sides of the bagworm, during spinning, and are bonded together by a sericin-like adhesive substance. In this specification, when "spun bagworm silk threads" or "spun bagworm silk threads" are used together with "spun threads," this is generally intended to mean spun fiber.

[0020] An "aggregate fiber" is a fiber composed of multiple fiber bundles, also called a multifilament. It is what is called raw silk, and in principle is composed of multiple single fibers, but in this specification it also includes cases where it is composed of multiple single fibers and spun fibers, or multiple spun fibers. In this specification, the aggregate fiber means an aggregate fiber composed only of bagworm silk threads. The aggregate fiber is twisted through a twisting process to become a stronger silk thread. However, in this specification, the aggregate fiber includes not only twisted fibers, but also non-twisted fibers that are soft and smooth to the touch.

[0021] Bagworm silk consists of scaffold silk and nest silk. "Scaffold silk" is silk that bagworms spin before moving, and functions as a scaffold to prevent them from falling off branches and leaves while moving. Bagworms usually use this scaffold silk as a foothold to hook the claws of both legs and move in the direction of their movement. Scaffold silk is spun in a zigzag pattern so that bagworms can easily hook their left and right legs, and to distribute the load on the silk thread's fixed parts and the silk thread to the left and right. On the other hand, "nest silk" is silk that makes up the nest, and is spun to bind pieces of leaves and branches together, and to create a comfortable environment for the inner walls of the nest, which are the living area. As a rule, scaffold silk is thicker and mechanically stronger than nest silk.

[0022] The method for obtaining bagworm silk is not particularly limited, but it is preferable to produce it by the method described in JP 2018-197415 A. In addition, modified bagworm silk excreted by genetically modified silkworms described in WO 2018 / 074403 A can also be used.

[0023] Bagworm silk has a special amino acid sequence and a highly ordered hierarchical structure, as described in Non-Patent Documents 1 and 2. The presence of such a special amino acid sequence and highly ordered hierarchical structure results in a fiber with excellent elastic modulus and strength. Bagworm silk consists of a fibril hierarchical structure, with nanofibrils as basic units, which are made up of a long-period repeating structure of crystalline and amorphous phases. The repeating unit of the primary structure is about 160 residues, which is about five times longer than that of spider silk. The greatest feature of bagworm silk is that it has a hybrid type that combines the polyalanine sequence and Gly-Gly-X (X is Ala, Tyr, etc.) sequence characteristic of spider silk, and the Gly-X (X is Ala, Ser, etc.) sequence characteristic of silkworms. The number of amino acid residues in the crystalline phase is thought to be 67 residues, which is several times longer than other silks (for example, silkworm silk), and the length of the period between the crystalline phase and the amorphous phase (long period), which is an indicator of the length of the crystalline phase, is also several times longer than other silks. In the formation of a hydrous gel, it is thought that the areas that are easy to form such a crystalline phase form a physical cross-linked structure, and the formation of a firm cross-linked structure is thought to affect the strength of the gel. It is believed that water molecules gather in the amorphous regions when a hydrogel is formed. As mentioned above, the repeating unit of the primary structure is 160 residues, of which 67 residues form the crystalline phase, so the amorphous phase is about 90 residues. It is believed that water molecules gather in the amorphous regions of these 90 residues.

[0024] The bagworm silk hydrogel of the present invention contains water as a solvent or dispersion medium. The water content in the gel may be any amount that can form a gel at 25° C. under atmospheric pressure, and can be appropriately adjusted depending on the strength and function of the desired hydrogel, as well as the properties of other additives. The water content of the hydrogel is preferably 80% by mass or more and 99.99% by mass or less based on the total amount of the gel, from the viewpoint of gelling at 25° C. and atmospheric pressure, more preferably 85% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more, more preferably 99.95% by mass or less, even more preferably 99.9% by mass or less, and even more preferably 99.5% by mass or less. In addition, the mass ratio (a / b) of bagworm silk (a) to water (b) varies depending on the strength, function, etc. of the hydrous gel, as well as the characteristics of other additives, but is preferably 0.0001 or more and 0.1765 or less, more preferably 0.0005 or more and 0.1111 or less, and even more preferably 0.005 or more and 0.0417 or less.

[0025] To prepare the bagworm silk-containing aqueous solution, in addition to water, an aqueous solvent that is advantageous for dissolving bagworm silk can be used. Examples of aqueous solvents include solutions in which neutral salts are dissolved in water, such as copper-ethylenediamine aqueous solution, copper hydroxide-ammonia aqueous solution, copper hydroxide-alkali-glycerin aqueous solution, lithium bromide aqueous solution, calcium chloride aqueous solution, magnesium chloride aqueous solution, zinc chloride aqueous solution, calcium nitrate aqueous solution, magnesium nitrate aqueous solution, zinc nitrate aqueous solution, calcium thiocyanate aqueous solution, magnesium thiocyanate aqueous solution, zinc thiocyanate aqueous solution, sodium thiocyanate aqueous solution, lithium thiocyanate aqueous solution, urea aqueous solution, and sodium dodecyl sulfate aqueous solution. In addition, water-containing alcohols obtained by mixing lower alcohols such as methanol and ethanol with water can also be used. In addition, from the viewpoint of dissolving bagworm silk, organic solvents such as hexafluoroacetone, dichloroacetic acid, trifluoroacetic acid, hexafluoroisopropanol, hexafluoroacetone, and formic acid can also be used. In addition to bagworm silk as a solute / dispersoid and water as a solvent / dispersion medium, the bagworm silk hydrogel of the present invention can contain various additives taking into consideration the strength of the hydrogel and the desired functions and characteristics. Additives that can be included include, for example, components that have high affinity with bagworm silk and water, gel-forming polymers, sugars, sugar alcohols, alcohols, polyhydric alcohols, water-soluble polymers, plasticizers, basic compounds such as organic bases and inorganic bases, pigments, etc. Examples of gel-forming polymers include synthetic polymers such as poly(meth)acrylic acid, poly(meth)acrylate, carboxyvinyl polymer, polyvinyl chloride, polyvinyl acetate, and salts thereof, and natural polymers such as cellulose derivatives and polysaccharides (agar, gelatin, carrageenan, pectin, gellan gum, xanthan gum, locust bean gum, tamarind seed gum, curdlan, etc.). Examples of sugars include monosaccharides, oligosaccharides, and oligosaccharides. Examples of sugar alcohols include erythritol, lactitol, maltitol, mannitol, sorbitol, and xylitol. Examples of alcohols include ethanol, isopropanol, and butanol. Examples of polyhydric alcohols include ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, glycerin, polyglycerin, butylene glycol, and polybutylene glycol. An example of the water-soluble polymer is polyvinyl alcohol. Examples of the plasticizer include triacetin, triethylene glycol diacetate, tributyl acetyl citrate, dibutyl sebacate, epoxidized soybean oil, phthalates, and adipates. Furthermore, basic compounds such as organic bases and inorganic bases act as crosslinking agents for acidic polymers such as polyacrylic acid. Examples of colorants include Food Red No. 2, Food Red No. 3, Food Red No. 40, Food Red No. 102, Food Red No. 106, Food Yellow No. 4, Food Yellow No. 5, Food Blue No. 1, Food Blue No. 2, and caramel.

[0026] The effects of these other components on the hydrogel of the present invention vary depending on the type thereof, so their content varies greatly, but the content is preferably 0.5% by mass or more and 60% by mass or less, more preferably 1% by mass or more and 45% by mass or less, and even more preferably 5% by mass or more and 30% by mass or less, based on the total amount of the gel. The bagworm silk-containing hydrogel of the present invention can be easily produced, for example, by heating an aqueous solution or aqueous dispersion containing bagworm silk (hereinafter, the aqueous solution or aqueous dispersion containing bagworm silk may be abbreviated as an aqueous solution containing bagworm silk) to 50° C. or higher and then cooling. If necessary, the aqueous solution containing bagworm silk may be subjected to a concentration process such as dialysis or ultrafiltration before heating. In the method for producing a bagworm silk-containing hydrogel of the present invention, first, an aqueous solution or dispersion containing bagworm silk is prepared. The bagworm silk-containing aqueous solution can be produced by adding a sufficient amount of water to the bagworm silk and, if necessary, additives. The additives may be added simultaneously with the water or separately. The heating temperature of the bagworm silk-containing aqueous solution is sufficient at 50° C. or higher, and more preferably at 60° C. or higher. The upper limit of the heating temperature may be 100° C. or higher, and is preferably 130° C. or lower in consideration of industrial productivity. Regarding the heating conditions, if the concentration of bagworm silk changes significantly when the bagworm silk-containing aqueous solution gels, it becomes difficult to obtain a gel with the desired properties, so it is preferable to set the conditions under which water evaporation during gelation is prevented and under which water molecules can pass through the solution or gel. Taking such conditions into consideration, it is preferable to fill the bagworm silk-containing aqueous solution into a container (mold) with a certain degree of water permeability and heat it. Containers (molds) for heating are not particularly limited, but examples include dialysis membrane containers, low-density polyethylene containers, and metal containers. Heating may be performed in water or in air. After sufficient gelation has been confirmed, the bagworm silk hydrogel of the present invention is obtained by cooling to 15 to 25°C. Furthermore, for example, when the container is a dialysis membrane, the water content in the gel can be adjusted by appropriately changing the solvent of the external liquid of the container. Furthermore, since no gel was obtained when an aqueous solution of silkworm silk was heated for a long period of time (heated at 80°C for 500 minutes) and then cooled, the method for producing a bagworm silk-containing gel of the present invention is industrially advantageous. In addition, when producing the bagworm silk hydrogel of the present invention, not only bagworm silk can be used, but also proteins having the amino acid sequence that constitutes bagworm silk, and proteins having an amino acid sequence in which one or more amino acids have been deleted, added and / or substituted based on known techniques.

[0027] If other ingredients (additives) such as polyvinyl alcohol and agar are added to the bagworm silk-containing aqueous solution, heated to above 50°C, and then cooled, a composite hydrogel consisting of bagworm silk, polyvinyl alcohol, and agar is obtained. The obtained hydrogel is soft but maintains its shape and has the property of being resilient. If a dialysis membrane is used as the container, evaporation of water is minimal and no deformation due to adhesion to the container occurs.

[0028] The bagworm silk hydrogel of the present invention can be made into a thixotropic gel that is solid at 15 to 25° C. but becomes fluid when shear force is applied, depending on the moisture content and other components (additives) added during gelation. Such gels can be used as medicines, cosmetics, foods, etc. It can also be made into a solid, elastic hydrogel, which can be used in foods, cosmetics, biomaterials, cushioning materials, elastic materials, fishing equipment, medical equipment, industrial materials, sanitary materials (such as diapers), etc. EXAMPLES

[0029] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0030] Example 1 Bagworm scaffold silk was used as the bagworm silk and was refined in a 0.02M sodium carbonate aqueous solution heated to 90°C for 30 minutes. 40 mg of the refined bagworm silk was dissolved in a saturated lithium thiocyanate aqueous solution heated to 70°C for 60 minutes, then placed in a cellulose dialysis tube and dialyzed using 2 liters of ultrapure water as the dialysis external solution. The dialysis temperature was set to 4°C, and the dialysis external solution was replaced twice a day for a total of four times. The concentration of the prepared bagworm silk aqueous solution was calculated to be 1.2% by mass by measuring the dry weight. The obtained bagworm silk aqueous solution was placed in a cellulose dialysis tube and air-dried and concentrated to prepare a 2% by mass bagworm silk aqueous solution. The obtained aqueous solution was sealed in a dialysis tube and heated in a warm bath at 38°C to 80°C. The relationship between heating time and gelation is shown in Table 1. Table 1 shows that an aqueous solution containing bagworm silk easily gels when heated to 50°C or higher. Furthermore, a 2% by mass aqueous solution of silkworm silk did not gel even when heated at 80°C for 500 minutes.

[0031] [Table 1]

[0032] Example 2 A 2% by mass aqueous solution of bagworm silk was placed in a dialysis membrane, a low-density polyethylene (LDPE) membrane, a sealed container (sample tube with lid) or in an open container (petri dish) and heated for 20 minutes under the conditions in Table 2, and the state of the resulting gel was observed. The temperature for underwater heating and dry thermo was 80°C. For dry heat treatment, heating was performed for 20 minutes in a dry heat sterilizer set to 80°C, and for autoclave treatment, heating was performed for 20 minutes at 121°C. The results are shown in Table 2. From Table 2, it can be seen that the best heating conditions are those that prevent water from evaporating during gelation and allow water molecules to pass between the inside and outside of the membrane (container).

[0033] [Table 2]

[0034] Example 3 Using the same method as in Example 1, 1 mL of bagworm silk aqueous solutions prepared to 0.005, 0.01, 0.05, 0.07, 0.1, 0.5, 0.75, 1, 2, 4, 5, 6, and 7% by mass were enclosed together with air bubbles in an 8 / 32 dialysis membrane and heated for 15 minutes in hot water at 90° C. After heating, gelation was judged based on the movement of the air bubbles when the dialysis membrane was turned upside down, and the dialysis membrane was then cut open to evaluate the form of the gel. The degree of gelation was judged based on the movement of air bubbles enclosed in the dialysis membrane. The evaluation criteria were as follows: ×: No change from before heating was observed. △: Movement is slightly slower than before gelation. ○: Movement is slower than before gelation. ⊚: The movement of the bubbles stops in the gel or the bubbles do not move. The results are shown in Table 3.

[0035] [Table 3]

[0036] Example 4 1 mL of 10% by mass polyvinyl alcohol aqueous solution and 100 mg of agar were placed in a 5 mL sample tube and dispersed by vigorously stirring with a vortex mixer. 1 mL of 2% by mass bagworm silk aqueous solution was added and mixed uniformly by pipetting. The mixture was sealed in a dialysis membrane and immersed in a 90°C water bath for 30 minutes, after which it was transferred to a saturated borax aqueous solution heated to 90°C and heated for another 30 minutes. The water was removed and cooled at 4°C for 5 minutes, after which the dialysis membrane was cut open to collect the gel. The surface smoothness, shape stability, and appearance of the gel obtained were evaluated. Surface smoothness was evaluated based on the roughness of the gel surface and the occurrence of peeling. Shape stability was evaluated based on whether the shape of the dialysis membrane container was maintained and whether the attached part with the membrane peeled off. Appearance was evaluated based on transparency, gloss, etc. The results are shown in Figure 1.

[0037] As shown in Figure 1, a composite hydrogel of bagworm silk, polyvinyl alcohol, and agar of the present invention was obtained, and its surface smoothness, shape stability, and appearance were all good. In addition, by placing it in a dialysis membrane and heating it in water, the polyvinyl alcohol did not dissolve. By placing it in a dialysis membrane and coming into contact with borax water, excess water escaped from the gel, causing the membrane to shrink and tighten. A gel structure was formed through three stages: gelation of bagworm silk → gelation of polyvinyl alcohol → gelation of agar.

[0038] Test Example 1 Comparison of physical properties between bagworm silk gel and silkworm silk water gel Tests were conducted to compare the physical properties of a hydrous gel containing silk from silkworms, which are silk-spinning insects like bagworms, with the hydrous gel of bagworm silk of the present invention. Using a method similar to that used in Example 1, a 2% by mass aqueous solution of bagworm silk and a 2% by mass aqueous solution of silkworm silk were prepared, and 2 mL of each was sealed in an 8 / 32 dialysis membrane. The obtained dialysis membrane was placed in a 50 mL tube containing 40 mL of ultrapure water that had been preheated to 100°C using a dry thermo unit, and heated to gel. The treatment was continued until gelation occurred by heating in water, and the gel was cut to a length of 10 mm and subjected to a uniaxial compression test (load cell: 50 N, pusher: φ23 mm, base Z=0, and the position where F>0.03 N was the gel height was measured at a compression speed of 1 mm / min up to 70%, n=9). The compressive elastic modulus was calculated from the stress and strain at strains of 0.05 to 0.25%, and the results up to the time when the gel first broke are shown in Table 4.

[0039] [Table 4]

[0040] Compared to the aqueous gel of silkworm silk, the aqueous gel of bagworm silk had a compressive elastic modulus 0.8 times, toughness 6.0 times, breaking displacement 2.3 times, and compressive fracture stress 3.7 times, demonstrating that it has extremely excellent physical properties.

Claims

1. A gel comprising (i) bagworm silk and (ii) water, A gel having a water content of 80% by mass or more and 99.99% by mass or less based on the total amount of the gel.

2. 2. The gel according to claim 1, further comprising one or more components selected from the group consisting of gel-forming polymers, sugars, sugar alcohols, ethanol, isopropanol, butanol, polyhydric alcohols, water-soluble polymers and basic substances.

3. 2. The gel according to claim 1, wherein the bagworm silk is silk produced by Eumeta japonica, Eumeta minuscula or Nipponopsyche fuscescens.

4. 4. A food, medicine, cosmetic, sanitary material, biomaterial, cushioning material, elastic material, fishing equipment, medical equipment or industrial material comprising the gel according to any one of claims 1 to 3.

5. A method for producing a gel containing (i) bagworm silk and (ii) water, characterized by heating an aqueous solution containing bagworm silk to 50°C or higher and then cooling it.

6. A method for producing a gel as described in claim 5, wherein the water content in the produced gel is 80 mass% or more and 99.99 mass% or less of the total amount of the gel.

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