Method for producing a gallol group-modified chitosan sheet, and a multilayer sheet comprising a gallol group-modified chitosan sheet.

Abstract

A manufacturing method that can provide a gallol group-modified chitosan sheet with excellent adhesive properties, and a multilayer sheet equipped with a gallol group-modified chitosan sheet with excellent adhesive properties are provided. [Means] A method for producing a gallol group-modified chitosan sheet, comprising the steps of: grinding gallol group-modified chitosan; and compressing the obtained pulverized material into a sheet.

Description

Technical Field

[0001] The present invention relates to a method for producing a gallol group-modified chitosan sheet and a multilayer sheet including the gallol group-modified chitosan sheet.

Background Art

[0002] Currently, as adhesive sheets used in surgery, an adhesive sheet (TachoSil (registered trademark)) in which human fibrinogen or the like is fixed to a sponge-like collagen sheet is used for purposes such as hemostasis, and an adhesive sheet (NeoBeer (registered trademark) + Bolheal (registered trademark)) in which a plasma fraction preparation is applied to a non-woven fabric made of polyglycolic acid is used for purposes such as preventing air leakage from the lung surface.

[0003] However, the adhesive strength to wet tissues is weak for all of them, and they will peel off if an attempt is made to peel them off. Therefore, there is a demand for the development of an adhesive sheet having higher adhesive strength and higher abilities such as hemostasis and prevention of air leakage from the lung surface.

[0004] One of the inventors of the present application has been developing an underwater adhesive focusing on the gallol group, which is the adhesion motif of barnacles that adhere to rocks and live in a state of being completely immersed in seawater (Patent Document 1). Furthermore, this gallol group is introduced into the side chain of chitosan, which is a kind of polysaccharide, and an adhesive composition that is an aqueous dispersion of gallol group-modified chitosan has been developed (Non-Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Non-Patent Documents

[0006]

Non-Patent Document 1

[0007] However, the adhesive composition described in Non-Patent Document 1 required several hours for the water to evaporate and the adhesive to bond, making it unsuitable for medical applications where rapid bonding is required.

[0008] Therefore, the object of the present invention is to provide a manufacturing method that can provide a gallol group-modified chitosan sheet with excellent adhesive properties, and a multilayer sheet equipped with a gallol group-modified chitosan sheet with excellent adhesive properties. [Means for solving the problem]

[0009] As a result of diligently investigating the above problems, the inventors of this invention have obtained the following findings. • By crushing gallol group-modified chitosan resin using a predetermined method and then compressing and molding it into a sheet, an adhesive gallol group-modified chitosan sheet can be obtained. The adhesion between a gallol group-modified chitosan sheet and a predetermined bioabsorbable sheet can be further improved by creating a multilayer structure.

[0010] Based on the above findings, the inventors have completed the following invention. [1] A method for producing a gallol group-modified chitosan sheet, comprising the steps of: grinding gallol group-modified chitosan of the following formula (1); and compressing the obtained pulverized material into a sheet.

[0011] [ka]

[0012] [2] A multilayer sheet comprising a sheet containing gallol group-modified chitosan represented by the following formula (1) and a bioabsorbable sheet.

[0013] [Chemical formula] [Advantages of the Invention]

[0014] According to the method for producing a gallol group-modified chitosan sheet of the present invention, a gallol group-modified chitosan sheet excellent in adhesiveness can be provided. Further, according to the multilayer sheet of the present invention, the adhesiveness of the gallol group-modified chitosan sheet can be further improved. [Brief Description of the Drawings]

[0015] [Figure 1] It is a graph showing the evaluation result of the adhesive strength of the gallol group-modified chitosan sheet to porcine skin. [Figure 2] Fig. 2(a) is a diagram showing the experimental procedure in the evaluation of the adhesive strength of the multilayer sheet. Fig. 2(b) is a graph showing the evaluation result of the adhesive strength of the multilayer sheet to porcine esophagus. [Modes for Carrying Out the Invention]

[0016] [Gallol Group-Modified Chitosan Sheet] The gallol group-modified chitosan sheet is a sheet containing gallol group-modified chitosan represented by the following formula (1) as a main component.

[0017] [Chemical formula]

[0018] Here, "main component" means that, based on the entire sheet as a reference (100% by mass), the sheet contains preferably 50% by mass or more of gallol group-modified chitosan represented by formula (1), more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and most preferably 95% by mass or more.

[0019] The gallol group-modified chitosan sheet may contain, in addition to gallol group-modified chitosan, other resins such as polyester, or additives such as genipine.

[0020] Gallol-modified chitosan has a structure in which a gallol group is bonded to the amino group of chitosan, and can be manufactured according to the following procedure.

[0021] [ka]

[0022] Gallol-modified chitosan can be obtained by reacting chitosan with 1-hydroxybenzotriazole (HOBt), and then reacting it with 3,4,5-trihydroxybenzoic acid (Gallic acid) in the presence of 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide Hydrochloride (EDC). Details of the method for producing gallol group-modified chitosan will be described in the Examples section below.

[0023] (Sheet density) The gallol group-modified chitosan sheet obtained by the method described below has a predetermined density. The density of the gallol group-modified chitosan sheet preferably has a lower limit of 0.1 g / cm³. 3 More preferably 0.2 g / cm³ 3 More preferably 0.3 g / cm³ 3 The above applies, with a preferred upper limit of 1.5 g / cm³. 3More preferably, 1.0 g / cm³ 3 More preferably, 0.6 g / cm³ 3 The following applies: If the sheet density is too low, the sheet strength may be inferior, and conversely, if the sheet density is too high, the sheet's adhesive properties may be inferior.

[0024] The thickness of the gallol group-modified chitosan sheet is preferably 0.1 to 6 mm, more preferably 0.4 to 5 mm.

[0025] <Method for producing gallol group-modified chitosan sheets> (Step of grinding the gallol group-modified chitosan of formula (1)) The solid gallol group-modified chitosan obtained by the above method is subjected to grinding. The grinding method is not particularly limited as long as the solid gallol group-modified chitosan can be ground into the predetermined cotton-like material shown below, but for example, it can be ground using a tube mill.

[0026] When grinding using a tube mill, the grinding conditions are such that the rotation speed is preferably 5,000 rpm or higher at the lower limit, more preferably 8,000 rpm or higher, even more preferably 10,000 rpm or higher, and particularly preferably 12,000 rpm or higher, and preferably 25,000 rpm or lower at the upper limit, more preferably 20,000 rpm or lower, and even more preferably 18,000 rpm or lower. If the rotation speed is too low, the fineness of the material after grinding may be too high. Conversely, if the rotation speed is too high, the ground material may overheat, causing the ground particles to fuse together.

[0027] Furthermore, the grinding time has a lower limit of preferably 10 seconds or more, more preferably 20 seconds or more, even more preferably 30 seconds or more, and particularly preferably 40 seconds or more, and an upper limit of preferably 5 minutes or less, more preferably 3 minutes or less, even more preferably 2 minutes or less, and particularly preferably 90 seconds or less. If the grinding time is too short, the resulting fineness may be too large. Conversely, if the grinding time is too long, the ground material may overheat, causing the granules to fuse together.

[0028] Other grinding methods besides tube mills include, for example, ball mills and bead mills.

[0029] After pulverization, the gallol group-modified chitosan forms a cotton-like material with intertwined fibrous resins.

[0030] (A process of compressing the obtained pulverized material into a sheet.) In this process, the cotton-like material obtained in the above process is compressed and molded into a sheet. The compression molding method is not particularly limited as long as a sheet of a predetermined thickness can be obtained, but for example, one method is to use a concave mold and a convex mold as predetermined molds for forming the sheet, place the cotton-like material in the concave mold, and press the convex mold to form the sheet.

[0031] A metal mold can be used as the casting mold; for example, an aluminum mold can be used. The concave mold may be divided into two parts: a frame-shaped mold and a lower mold.

[0032] The pressing pressure has a lower limit of preferably 10kPa or more, more preferably 15kPa or more, even more preferably 18kPa or more, and particularly preferably 20kPa or more, and an upper limit of preferably 40kPa or less, more preferably 35kPa or less, even more preferably 30kPa or less, and particularly preferably 25kPa or less. If the pressing pressure is too low, the resulting sheet strength may be inferior, and conversely, if the pressing pressure is too high, the sheet density may become too high, making it difficult to achieve the desired adhesive strength.

[0033] The pressing time has a lower limit of preferably 1 minute or more, more preferably 2 minutes or more, even more preferably 3 minutes or more, and particularly preferably 4 minutes or more, and an upper limit of preferably 10 minutes or less, more preferably 8 minutes or less, even more preferably 7 minutes or less, and particularly preferably 6 minutes or less. If the pressing time is too short, the resulting sheet strength may be insufficient. Conversely, if the pressing time is too long, the sheet density may become too high, making it difficult to achieve the desired adhesive strength.

[0034] By extracting from the above form, a gallol group-modified chitosan sheet can be obtained.

[0035] <Multilayer sheet> The multilayer sheet of the present invention is a multilayer sheet comprising a sheet containing the gallol group-modified chitosan of the following formula (1) as described above, and a bioabsorbable sheet.

[0036] [ka]

[0037] (Bioabsorbable sheet) A bioabsorbable sheet is a sheet that has the property of being broken down and absorbed within the body. The breakdown can be enzymatic or non-enzymatic. A bioabsorbable sheet is a sheet containing a bioabsorbable resin. Examples of bioabsorbable resins include polyglycolic acid, L-lactic acid-glycolic acid copolymer, D,L-lactic acid-glycolic acid copolymer, glycolic acid-ε-caprolactone copolymer, poly-L-lactic acid, poly-D,L-lactic acid, copolymer of L-lactide and ε-caprolactone, poly-ε-caprolactone, and poly-p-dioxanone. In particular, from the viewpoint of sheet strength and degradation characteristics, a copolymer of L-lactide and ε-caprolactone is preferred as the bioabsorbable resin.

[0038] A sheet containing bioabsorbable resin is a sheet that contains bioabsorbable resin as its main component.

[0039] Here, "main component" means that, based on the entire sheet (100% by mass), the bioabsorbable resin is preferably present in an amount of 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and most preferably 95% by mass or more.

[0040] A preferred form of the sheet containing a copolymer of L-lactide and ε-caprolactone may also contain, in addition to the copolymer of L-lactide and ε-caprolactone, other bioabsorbable resins such as polyglycolic acid, or additives such as vitamin C.

[0041] A copolymer of L-lactide and ε-caprolactone can be obtained by ring-opening copolymerization of L-lactide and ε-caprolactone. The copolymerization ratio of L-lactide to ε-caprolactone is not particularly limited, but is preferably 40-80:60-20 (L-lactide:ε-caprolactone), and more preferably 50-75:50-25 (L-lactide:ε-caprolactone).

[0042] The method for forming bioabsorbable sheets is not particularly limited, but one example is to form them by heat-pressing the synthesized polymer. For example, the conditions for hot pressing can be a press pressure of 1 to 10 kPa, a press temperature of 70 to 150°C, and a press time of 5 to 15 minutes.

[0043] Furthermore, the thickness of the bioabsorbable sheet is preferably 1 μm or more and 1000 μm or less.

[0044] (Other layers) The multilayer sheet may include other layers in addition to the sheet containing the gallol group-modified chitosan described above and the bioabsorbable sheet. Other layers may include, for example, a rigid layer or a release layer. These other layers are selected as appropriate depending on the further functions that you wish to impart to the resulting multilayer sheet.

[0045] Furthermore, the multilayer sheet may have adhesive layers between the layers. For example, the adhesive layer can be made of ethylene vinyl acetate copolymer (EVA) resin or thermoplastic poly(ε-caprolactone) resin.

[0046] <Manufacturing method for multilayer sheets> The multilayer sheet of the present invention can be manufactured by laminating the above-mentioned sheets (gallol group modified chitosan sheet, bioabsorbable sheet, and other sheets constituting the layers).

[0047] The gallol group-modified chitosan sheet exhibits adhesion to wet surfaces such as those of living organisms. Therefore, by applying a solvent to the surface of the bioabsorbable sheet described above, and then laminating the gallol group-modified chitosan sheet onto the solvent-coated surface, a multilayer sheet can be manufactured by bonding the gallol group-modified chitosan sheet and the bioabsorbable sheet together.

[0048] While water and dimethyl sulfoxide can be used as solvents, dimethyl sulfoxide is preferred because it is easier to remove the solvent in the subsequent drying process.

[0049] Alternatively, the adhesive layer described above may be applied separately to either a gallol group-modified chitosan sheet or a bioabsorbable sheet, or both, and then bonded together to produce a multilayer sheet. After bonding, the multilayer sheets may be pressed and held for a certain period of time, if necessary, to improve adhesion.

[0050] Furthermore, as described above, after laminating each sheet, it is preferable to perform a drying treatment to remove the solvent used. The drying method is not particularly limited as long as it can remove the solvent used, but for example, a drying desiccator can be used. The drying time can preferably be 3 minutes to 24 hours. [Examples]

[0051] (Synthesis of gallol-modified chitosan) 1 g of chitosan was dissolved in 100 mL of deionized water, and 1 g of 1-hydroxybenzotriazole (HOBt) was added to it. The resulting solution was stirred overnight to completely dissolve the chitosan. Subsequently, 1.0 g of 3,4,5-trihydroxybenzoic acid (Gallic Acid) was added to the resulting solution, and 1.13 g of EDC-HCl solution dissolved in 1 mL of ethanol was added dropwise.

[0052] The solution obtained above was stirred for 24 hours, and then dialyzed over 3 days with MES buffer (17 mM) containing 150 mM NaCl, followed by dialyzation over 6 hours with distilled water. Spectra / Por 7, MWCO 50 kDa, and Repligen were used as the dialysis membranes. Subsequently, the obtained solution was freeze-dried using a freeze-dryer (FDS-2000, EYELA, Tokyo, Japan) to obtain solid gallol group-modified chitosan.

[0053] (Synthesis of a copolymer of L-lactide and ε-caprolactone (bioabsorbable resin)) The copolymer of L-lactide and ε-caprolactone was obtained by ring-opening polymerization of L-lactide and ε-caprolactone according to a known method. Specifically, the process was as follows: 4.0 g of L-lactide and 1.6 g of ε-caprolactone were mixed with 5.7 mg of tin(II) 2-ethylhexanoate as a catalyst and reacted under a nitrogen atmosphere at 150°C for 24 hours. After the reaction, the mixture was dissolved in 30 mL of dichloromethane and added dropwise to 300 mL of cooled ethanol. The precipitated components were recovered by suction filtration and dried under reduced pressure to obtain the copolymer.

[0054] (Manufacturing of gallol group-modified chitosan sheets) The solid gallol group-modified chitosan obtained above was pulverized in a tube mill (IKA, Germany) at 15,000 rpm for 1 minute, and then pressed in an aluminum mold (22 kPa, 5 minutes) to obtain a gallol group-modified chitosan sheet with a thickness of approximately 400 μm.

[0055] (Manufacturing of a copolymer sheet of L-lactide and ε-caprolactone (bioabsorbable sheet)) The copolymer synthesized above was formed into a sheet (thickness: 150 μm) by hot pressing (4 kPa, 120°C, 10 minutes).

[0056] (Manufacturing of multilayer sheets) 100 μL of dimethyl sulfoxide was applied to the above bioabsorbable sheet (1.5 cm x 3 cm) using a brush, and the above gallol group-modified chitosan sheet was laminated onto it. After that, it was dried in a vacuum desiccator to remove the dimethyl sulfoxide and produce a multilayer sheet.

[0057] (Evaluation of adhesive strength of gallol group-modified chitosan sheets) The adhesive strength of gallol group-modified chitosan sheets was evaluated using the following procedure. The evaluation results are shown in Figure 1. Sample preparation procedure: A pigskin (2cm x 6cm) was cut in half (2cm x 3cm). The cut surfaces were joined together by layering a 400μm thick gallol group-modified chitosan sheet (Example) or a TacoSeal (Comparative Example) to create a test specimen. (The test was conducted in the same manner as shown in Figure 2(a) below, except that pigskin was used instead of pig esophagus, and the gallol group-modified chitosan sheet from the Example or the TacoSeal from the Comparative Example was used instead of the two-layer sheet.) For Volheel (Comparative Example), the cut surfaces were sprayed and joined together to create a test specimen. Evaluation method: Using a tensile testing machine, the ends of the above test specimens were gripped and pulled at a speed of 10 mm per minute in the direction away from each other, and the adhesive strength was measured.

[0058] For comparative examples, the commercially available bio-adhesives used are as follows: TacoSeal (registered trademark): Sheet-type biological tissue adhesive and occlusive agent, manufactured by CSL Behring. Volheal (registered trademark): Plasma-derived product (bio-tissue adhesive), manufactured by KM Biologics.

[0059] As shown in Figure 1, the gallol-modified chitosan sheet obtained by the manufacturing method of the present invention was found to have superior adhesive strength compared to conventional commercially available bioadhesives.

[0060] (Evaluation of adhesive strength of multilayer sheets) To assess the adhesive strength of the multilayer sheets, the pig esophagus was used. As shown in Figure 2(a), the pig esophagus was butted together, and the gallol group-modified chitosan sheet (Cs-gal) and the multilayer sheet (Cs-gal / P(LLA-co‐CL)) prepared above were bonded to the butt joint. The adhesive strength was then measured by pulling in the direction shown in Figure 2(a). The multilayer sheets were bonded together so that the gallol group-modified chitosan sheet side faced the pig's esophagus.

[0061] The results are shown in Figure 2(b). Sufficient adhesion was observed even with the gallol group-modified chitosan sheet (single-layer sheet), but further improvement in adhesion was observed with the multi-layer sheet. This is thought to be because the strength of the gallol group-modified chitosan sheet was reinforced by the bioabsorbable sheet, improving the strength of the sheet itself.

Claims

1. The process involves grinding the gallol group-modified chitosan of the following formula (1), and A process of compressing the obtained pulverized material into a sheet, A method for producing a gallol group-modified chitosan sheet, comprising the following: 【Chemistry 1】

2. A sheet containing gallol group-modified chitosan of the following formula (1), and Bioabsorbable sheet, A multi-layer sheet equipped with these features. 【Chemistry 2】

Images