KR20210141200A - Coating layer comprising pullulan and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a coating film comprising an iron ion-tannic acid coating layer containing iron ions and tannic acid, and a pullulan coating layer containing pullulan and a manufacturing method thereof. The coating film provided by the present invention can be manufactured in a short time under mild conditions, is edible by maintaining physical and chemical properties of pullulan as it is, is degradable in an acidic environment, and has biocompatible and antifouling surface properties.

Description

Coating layer comprising pullulan and manufacturing method thereof

The present invention relates to a coating film containing pullulan, a method for manufacturing the coating film, and its use, and more specifically, it is applicable to all coating objects under mild conditions, thickness control is possible, edible, natural decomposition, , A coating film composition comprising a pullulan multinuclear complex having biocompatible and antifouling properties, and a method for preparing the coating film and uses thereof are provided.

Natural polysaccharides are readily available biomass, which are converted into monosaccharides through catabolism and used for energy metabolism or as basic materials for forming living tissues through combination with proteins. Research on natural polysaccharides has been steadily conducted in terms of biomaterials, and in particular, research on diagnosis and therapeutics development in the medical and biomedical engineering fields is being actively conducted.

However, natural polysaccharides are mainly neutral and have a problem in that it is difficult to form and control the structure in an aqueous solution and to immobilize them because of their high solubility. To solve this problem, a polysaccharide derivative (typically carboxymethylcellulose; CMC) having a carboxylic acid (-COOH) formed so that a natural polysaccharide has a negative charge under biocompatibility conditions or a polysaccharide derivative having an amine (-NH ₂ ) formed so that a natural polysaccharide has a positive charge Research on ionic polysaccharides, which are derivatives of natural polysaccharides, is being actively conducted, such as basic and applied research using (chitosan; CHI) being actively conducted.

In the surface modification method, attempts are actively being made to combine the negatively and/or positively charged polysaccharide derivative with a multilayer thin film stacking method (Layer-by-Layer (LbL) assembly). The multi-layer thin film lamination method is a technology that uses strong electrostatic attraction from opposite charges, and has the advantage of easy control of the thickness, roughness, and surface morphology of the obtained nanofilm. If negatively and positively charged polysaccharide derivatives are used, this technology can be applied to any material having an electric charge, so it is possible to bind not only polymers, nanotubes, nanoparticles, but also biomaterials such as DNA, RNA, proteins, etc. It can be widely applied in fields such as energy and biosensors.

However, ionic polysaccharide derivatives have inevitable problems such as inducing non-specific binding to cause a problem in which ionic polysaccharides are fixed at unwanted positions due to their high charge density, and when compared with natural polysaccharides, It is slow to decompose in vivo, and there is a possibility of inducing inflammation due to DNA interference or binding to cell membranes or accumulation in living organs.

Pullulan is a natural high molecular polysaccharide produced from Aureobasidium pullulans , a type of fungus. It has a linear structure in which maltotriose units composed of alpha-1,4-glycosidic bonds are linked by alpha-1,6-glycosidic bonds. has a Pullulan has been used as a food packaging material or film material because it is easy to make a film and has excellent moisture retention. is becoming

In pullulan, there are 9 hydroxy groups per maltotriose unit, and these groups can be easily replaced with a desired chemical moiety through a chemical reaction. Until now, most studies have applied chemically neutral pullulan to ionic pullulan derivatives through chemical functionalization to make nanoparticles or nanogels. However, when pullulan is chemically modified in this way, the disadvantages of the above-described ionic polysaccharides appear, and there is a concern that biocompatibility may be reduced.

On the other hand, tannic acid is a natural plant extract contained in green tea and red wine, and is a polyphenol containing a galloyl group with three hydroxyl groups attached to a benzene ring. Because tannic acid rapidly complexes with trivalent iron ions, it is possible to form biocompatible and edible nanofilms in a fast and simple manner, regardless of the material.

An object of the present invention is an iron ion-tannic acid coating layer comprising iron ions and tannic acid; And the iron ion-to provide a coating film laminated on the tannic acid coating layer, the coating film comprising a pullulan coating layer containing pullulan, and a manufacturing method and use thereof.

The coating film can be coated regardless of the coating target under mild conditions, the thickness can be adjusted at the nanometer level, and has biocompatible, edible properties. In addition, the coating film is environmentally friendly because it can decompose naturally.

The present invention provides an iron ion-tannic acid coating layer comprising iron ions and tannic acid; And the iron ion is laminated on the tannic acid coating layer, and provides a coating film comprising a pullulan coating layer containing pullulan, a method for producing the coating film, and uses thereof.

Hereinafter, the present invention will be described in more detail.

In the present specification, the iron ion-tannic acid coating layer may be represented by "Fe(III)-TA", and the pullulan coating layer may be represented by "Pullulan", or "Pul".

In the present specification, each coating layer constituting the coating film may be represented by being separated by a symbol "/" in the order of coating from the surface of the coating target, and when each coating layer is repeatedly laminated, it will be represented by the number 'n' of the subscript. can The number n may be a natural number, and may be omitted when n is 1. In one example, the coating film in which one pullulan coating layer is formed on one iron ion-tannic acid coating layer is "[Fe(III)-TA/Pul] coating film" or "[Fe(III)-TA/Pullulan] coating film" can be expressed as In another example, when the coating film is repeatedly laminated twice, it may be expressed as _{"[Fe(III)-TA/Pul] 2 coating film".}

As used herein, "mild conditions" means conditions in which temperature and/or pH conditions are not severe, conditions that do not include a heating step and/or a cooling step, and/or conditions in which no acid or base catalyst is used. . The acid catalyst may be, for example, at least one selected from the group consisting of hydrochloric acid, nitric acid, acetic acid, sulfuric acid and hydrofluoric acid, and the base catalyst is, for example, one selected from the group consisting of aqueous ammonia, sodium hydroxide and potassium hydroxide. may be more than one species. In one embodiment, the mild pH conditions are pH 5.5 to 8.5, pH 5.5 to 8.0, pH 5.5 to 7.5, pH 6.0 to 8.5, pH 6.0 to 8.0, pH 6.0 to 7.5, pH 6.5 to 8.5, pH 6.5 to 8.0, pH 6.5 to 7.5, pH 7.0 to 8.5, pH 7.0 to 8.0, or pH 7.0 to 7.5. In one embodiment, the mild temperature conditions are room temperature, for example, 15 to 35 degrees Celsius, 15 to 30 degrees Celsius, 15 to 27 degrees Celsius, 18 to 35 degrees Celsius, 18 to 30 degrees Celsius. 18 to 27 degrees Celsius, 20 to 35 degrees Celsius, 20 to 30 degrees Celsius, 20 to 27 degrees Celsius, 23 to 35 degrees Celsius, 23 to 30 degrees Celsius, or 23 to 27 degrees Celsius, but is not limited thereto. .

In the present invention, "coating object", and/or "coating substrate" (substrate) means a film or an object or object to be coated, and may be used regardless of type as long as it has mass and volume. For example, the coating target may be at least one selected from inanimate objects such as metal, metal oxide, ceramic, mineral, polymer, glass, and/or wood. In another example, the coating target may be one or more selected from living organisms such as fungi (eg, bacteria, fungi, etc.), plants, animals, and the like, and may be an object in which an inanimate organism and an organism are combined. When the coating target is a plant or animal, it may be the plant or animal itself, or an organ or cell isolated therefrom. In one example, the coating target may be a pullulan coating layer formed on the surface.

The present invention provides an iron ion-tannic acid coating layer comprising iron ions and tannic acid; And the iron ion is laminated on the tannic acid coating layer, it provides a coating film comprising a pullulan coating layer comprising pullulan. The pullulan coating layer may further include iron ions.

The iron ion-tannic acid coating layer and the pullulan coating layer may constitute one unit coating layer, and the unit coating layer may be stacked once or by accumulating multiple times. The unit coating layer may have a form in which a pullulan coating layer is laminated on an iron ion-tannic acid coating layer and/or an iron ion-tannic acid coating layer is laminated on the pullulan coating layer. The number of accumulations may be appropriately adjusted according to the thickness of the desired coating film. For example, it may be 30 times or less, 25 times or less, or 20 times or less, but is not limited thereto.

The coating film provided by the present invention does not include the step of chemically functionalizing pullulan, thereby providing a surface having unique properties of pullulan. For example, it may have edible, biocompatible, and/or hydrophilic properties.

The coating film provided by the present invention may also have antifouling and/or acid resistance.

In one embodiment, the coating film provided by the present invention may have a superhydrophilic surface, for example, the contact angle between the coating film and water droplets may be 15 ° or less, 10 ° or less, 7 ° or less, or 5 ° or less, but limited thereto it's not going to be

In one embodiment, the coating film provided by the present invention has antifouling properties, and in one embodiment, the antifouling properties may mean properties that prevent adhesion of proteins and/or organic matter. In one embodiment, the iron ion-tannic acid coating film and the iron ion-tannic acid/pullulan coating film were respectively prepared and exposed to BSA to measure the contact angle of water before and after exposure. As a result, the iron ion-tannic acid coating film is the contact angle of water after exposure to BSA Although this increased more than twice, the iron ion-tannic acid/pullulan coating film maintains super-hydrophobic properties regardless of the reaction with proteins and/or organic matter in BSA with all contact angles of water before and after contamination of 5° or less, and has antifouling properties. was confirmed.

In one embodiment, the coating film provided by the present invention may have acid resistance. In one embodiment, the iron ion-tannic acid coating film ([Fe(III)-TA] ₄ ) without the pullulan coating layer and the [Fe(III)-TA/Pul] ₂ coating film including the pullulan coating layer are prepared, respectively As a result of observing the change in the thickness of the coating film by reacting with hydrochloric acid of pH 2, the iron ion-tannic acid coating film almost lost its thickness to 40% of the level before the reaction even after reacting with hydrochloric acid for 5 minutes, but [Fe(III) )-TA/Pul] ₂ coating film had a thickness of 40% of the pre-reaction thickness only after 1 day after the reaction, confirming that it had superior acid resistance compared to the iron ion-tannic acid coating film.

In one example, the coating film provided by the present invention may have acid resistance to acids of less than pH 7, less than pH 6, less than pH 5, less than pH 4, less than pH 3, or less than pH 2.

In one example, the coating film provided by the present invention may have a coating film thickness retention rate (Coating Remaining, %) of 40% or more, 45% or more, 50% or more, or 55% or more when reacted with an acid of pH 2 for 1 hour, but limited thereto doesn't happen The thickness retention rate is obtained as a percentage of the value obtained by dividing the thickness of the coating film after the reaction by the thickness of the coating film before the reaction.

The iron ion-tannic acid coating layer included in the coating film of the present invention can be coated regardless of the physical and chemical properties of the coating object, thereby contributing to the formation of a hybrid coating film without limitation. The iron ion-tannic acid coating layer may include a galloyl group, and the galloyl group may perform a function of helping a pullulan coating layer including a pullulan polynuclear complex to be formed on the iron ion-tannic acid coating layer.

The iron ion-tannic acid coating layer may have a characteristic of increasing the thickness by repeating the step of forming the iron ion-tannic acid coating layer a plurality of times, thereby providing a coating film capable of controlling the thickness at the nanometer level.

The iron ion-tannic acid coating layer may have a carbon/oxygen ratio (C/O ratio) on the surface of the coating layer of 1.5 to 1.8, 1.5 to 1.7, 1.6 to 1.8, or 1.6 to 1.7. The carbon/oxygen ratio (C/O ratio) may be expressed as a ratio of the number of atoms, that is, a value obtained by dividing the number of carbon atoms by the number of oxygen atoms.

Formation of the iron ion-tannic acid coating layer may be performed by a method comprising contacting a coating target (eg, a substrate) with an iron ion solution and contacting the tannic acid solution. The iron ion solution and the tannic acid solution may be sequentially added, and in one example, the iron ion solution may be first added and then the tannic acid solution may be added, but the present invention is not limited thereto. can be done freely.

In one example, the content ratio of iron ions and tannic acid in the iron ion-tannic acid coating layer (ratio of iron ions to the number of tannic acid molecules is 1:5 to 1:1, 1:4 to 1:1, 1:5 to 1:2) Or 1:4 to 1:2 may be, but is not limited thereto.

The iron ion-tannic acid coating layer may be generated under mild conditions. Since the coating layer is formed under mild conditions, there is an advantage that coating can be performed regardless of the coating target. The 'mild conditions' are the same as described above.

The pullulan coating layer included in the coating film of the present invention may further include iron ions in addition to pullulan. In one example, pullulan and iron ions form a multinuclear complex to form a film structure. In one example, the pullulan coating layer may be formed through a coordination bond of pullulan with iron ions. Similar to the iron ion-tannic acid coating layer, in the pullulan coating layer, it is expected that the iron ions will coordinate with 1 to 3 units of the OH groups of the pullulan molecule.

The pullulan coating layer may maintain physical and/or chemical properties of pullulan, for example, may have edible properties and/or biocompatibility properties.

The pullulan coating layer, when the iron ion-tannic acid coating layer is repeatedly laminated, may serve to help the formation of the iron ion-tannic acid coating layer. In one example, the iron ion-tannic acid coating layer formed on the pullulan coating layer was formed to be 1.5 to 3.5 times thicker than the iron ion-tannic acid coating layer formed on a general gold plate.

The C/O ratio (ratio of the number of C and O) of the pullulan coating layer surface may be 1.1 to 1.5, 1.1 to 1.4, or 1.1 to 1.3, but is not limited thereto.

The coating film provided by the present invention by the edible and / or biocompatibility characteristics can be utilized as a coating agent for food and / or a coating agent for pharmaceuticals.

In the coating film provided by the present invention, the thickness of the iron ion-tannic acid coating layer and the pullulan coating layer is 1:1 to 10:1, 1:1 to 5:1, or 1:1 to 1:3 (iron ion- Tannic acid coating layer thickness: pullulang coating layer thickness, hereinafter the same) can be prepared. In one example, the ratio of the thickness of each coating layer may be gradually lowered as the accumulation of the coating layer is repeated.

In one example, when the iron ion-tannic acid coating layer and the pullulan coating layer are repeatedly laminated in the coating film provided by the present invention, the thickness of the iron ion-tannic acid coating layer changes depending on the iron ion concentration in the coating solution used to form the pullulan coating layer can do.

In one embodiment, the concentration of iron ions in the pullulan coating solution is adjusted to 0 mg/mL (not included), 0.1 mg/mL, or 1 mg/mL to prepare a coating film, and as a result of measuring the thickness of the coating film at each layer formation, When no iron ions were added (0 mg/mL) or when the iron ion concentration was 1 mg/mL, a very thin thin film was formed within about 2 nm of each pullulan coating layer, and the thickness of the iron ion-tannic acid coating layer The thickness of each coating layer was formed at an average level of 3 nm in FIG. When the iron ion concentration is 0.1 mg/mL, the thickness of the iron ion-tannic acid coating layer formed on the pullulan coating layer is 6 to 11 nm, and the iron ion concentration affects the formation of the iron ion-tannic acid coating layer and the pullulan coating layer. Insanity was confirmed.

An example of the present invention relates to a coating agent for food, including a coating film including the iron ion-tannic acid coating layer and the pullulan coating layer. The properties of the coating film are as described above.

The food may include a health functional food, and the formulation is not limited. The formulation of the food may be, for example, one or more formulations selected from the group consisting of tablets, capsules, pills, granules, liquids, powders, syrups, flakes, jellies, bars, pastes, films and/or gels, but limited thereto doesn't happen In one example, the formulation of the food may be solid or semi-solid, for example, one or more selected from the group consisting of tablets, capsules, pills, powders, syrups, pieces, jellies, pastes, gels, films and bars. It may be in the form

Since the coating film provided by the present invention is edible, it is suitable for use as a coating agent for food. In addition, since it can be manufactured under mild conditions, it does not affect the characteristics such as nutrients, taste, and/or flavor of the food to be coated. When the food is a health functional food, the physical and / Alternatively, there is an advantage that does not affect the chemical properties.

The food coating agent may further include a food coating agent that can be used foodologically.

An example of the present invention relates to a coating agent for pharmaceuticals, including a coating film comprising the iron ion-tannic acid coating layer and the pullulan coating layer. The coating film is as described above.

As used herein, "coating agent for pharmaceuticals" refers to a thin film or film added to the active ingredient as a material other than the active ingredient of the drug. The coating agent is a kind of pharmaceutical additive, and is added to increase the usefulness of the drug and to facilitate formulation, and may be added in an appropriate dose within a range that does not change the therapeutic effect of the drug or interfere with the test.

The coating film included in the coating agent for pharmaceuticals provided by the present invention is edible, so it can be used as a coating agent for pharmaceuticals for oral administration. In one example, the drug to be coated may be administered by oral administration, attachment, suppository and/or sublingual tablet method. The pharmaceutical may be solid or semi-solid, and may be in the form of, for example, capsules, tablets, pills, powders, granules, syrups, patches, and/or jellies.

The coating film included in the coating agent for pharmaceuticals maintains the physical and/or chemical properties of pullulan and has biocompatible properties, so it is suitable for use as a coating agent for pharmaceuticals. In addition, since it can be manufactured under mild conditions, it has the advantage of lowering the manufacturing cost and not affecting the physical/chemical structure of the active ingredient of the drug to be coated.

The pharmaceutical coating agent may further include a pharmaceutical coating agent that can be used medically and/or pharmaceutically.

The coating method provided by the present invention comprises: a first step of forming an iron ion-tannic acid coating layer comprising iron ions and tannic acid on a coating object; and a second step of forming a pullulan coating layer including iron pullulan on the iron ion-tannic acid coating layer. The pullulan coating layer may further include iron ions.

In the coating method provided by the present invention, each coating layer forming step of the first step and the second step is to freely select any coating method within the objective range for forming a coating film on the surface of the object to be coated under mild conditions. can be performed. In one example, the coating method may be application (coating), immersion, or deposition on the surface to be coated. Specifically, the coating method may use one or more methods selected from the group consisting of paint brushing, spray coating, doctor blade, dip-pull method, and spin coating, but is not limited thereto.

The first to second steps may include contacting the coating solution with the coating target; and washing and drying the coating object in contact with the coating solution. The solvent of the coating solution may be appropriately selected depending on the purpose of the coating, for example, may be one or more solvents selected from the group consisting of deionized water, distilled water, sodium chloride aqueous solution and phosphate buffered saline.

All of the steps of forming the coating layer may be performed under mild conditions, and the mild conditions are as described above. The coating method provided by the present invention does not require a separate heating and/or cooling step, and the coating time and cost can be saved because each coating layer is formed within a short time, so that it is excellent in economic efficiency.

In the step of forming the coating layer, the contact time of the coating solution and the coating target in the step of contacting the coating solution and the coating target may be appropriately selected within the objective range for forming the coating film, for example, from 10 seconds to 180 minutes, 10 seconds to 120 minutes, 10 seconds to 60 minutes, 10 seconds to 30 minutes, 10 seconds to 20 minutes, 10 seconds to 10 minutes, 30 seconds to 180 minutes, 30 seconds to 120 minutes, 30 seconds to 60 minutes , 30 seconds to 30 minutes, 30 seconds to 20 minutes, 30 seconds to 10 minutes, 1 minute to 180 minutes, 1 minute to 120 minutes, 1 minute to 60 minutes, 1 minute to 30 minutes, 1 minute to 20 minutes, or It may be 1 minute to 10 minutes. In one embodiment, the iron ion-tannic acid coating layer was formed by reacting the coating solution with the coating target for 1 minute, and the pullulan coating layer was formed by reacting the coating solution with the coating target for 10 minutes.

Hereinafter, each step will be described in more detail.

The coating method provided by the present invention includes (1) a first step of forming an iron ion-tannic acid coating layer comprising iron ions and tannic acid on a coating object.

The iron ion-tannic acid coating layer is as described above.

In one example, before the first step, the step of forming a pullulan coating layer on the coating target may be additionally performed. The pullulan coating layer may include pullulan and further include iron ions.

The first step may be repeated a single time or a plurality of times before performing the second step. The iron ion-tannic acid coating layer may have a characteristic of increasing the thickness by repeating the step of forming the iron ion-tannic acid coating layer a plurality of times, thereby providing a coating film capable of controlling the thickness at the nanometer level.

Formation of the iron ion-tannic acid coating layer may be performed by a method comprising contacting a coating target (eg, a substrate) with an iron ion solution and contacting the tannic acid solution. The iron ion solution and the tannic acid solution may be sequentially added, and in one example, the iron ion solution may be added first and then the tannic acid solution may be added, but the present invention is not limited thereto. can be done freely.

The iron ion solution may be freely prepared and used within the intended range for including Fe(III) ions, for example, iron chloride hexahydrate (FeCl ₃ .6H ₂ O), iron nitrate heptahydrate (Fe(NO _{3 )} ) ₃ ·9H ₂ O) and iron sulfate heptahydrate (FeSO ₄ ·7H ₂ O) may be one or more solutions selected from the group consisting of, but is not limited thereto. The concentration of the iron ion solution can be freely adjusted within the range for the purpose of forming the iron ion-tannic acid coating film, for example, 1 to 100 mg/mL, 1 to 50 mg/mL, 1 to 30 mg/mL, 1 to 20 mg/mL, 3-100 mg/mL, 3-50 mg/mL, 3-30 mg/mL, 3-20 mg/mL, 5-100 mg/mL, 5-50 mg/mL, 5-30 mg /mL, 5-20 mg/mL, 7-100 mg/mL, 7-50 mg/mL, 7-30 mg/mL, or 7-20 mg/mL.

The concentration of tannic acid in the tannic acid solution can be freely adjusted within the range for the purpose of forming a coating film, for example, 5-200 mg/mL, 5-100 mg/mL, 5-70 mg/mL, 5-50 mg/mL, 10-200 mg/mL mL, 10-100 mg/mL, 10-70 mg/mL, 10-50 mg/mL, 30-200 mg/mL, 30-100 mg/mL, 30-70 mg/mL, or 30-50 mg/mL.

In one embodiment, 40 mg/mL distilled water aqueous solution of tannic acid and 10 mg/mL distilled water solution of FeCl ₃ ·6H ₂ O were prepared and used as stock solutions for coating.

The formation of the iron ion-tannic acid coating layer is mainly affected by the iron ion concentration, and the higher the iron ion concentration, the thicker the coating layer becomes and the roughness increases. If the concentration of iron ions is lower than the above range, the coating layer may not be formed normally, and when the concentration of the tannic acid and iron ion solution is above the above range, particles are rapidly formed in the aqueous solution, so there is a problem that the coating film is unevenly and irregularly formed. .

The iron ion-tannic acid coating layer formed by the first step serves to enable control of the thickness of the coating film by a multi-layered thin film lamination method (Layer-by-layer; LbL). _{In one embodiment, as a result of forming a [Pul] n} coating film by repeatedly laminating only the pullulan coating layer without performing the iron ion-tannic acid coating, a significant increase in the thickness of the coating film was not observed regardless of the number of laminations, so the iron ion- It was confirmed that the tannic acid coating layer plays a key role in thickness control.

The coating method provided by the present invention includes a second step of (2) forming a pullulan coating layer containing pullulan on the iron ion-tannic acid coating layer. The pullulan coating layer may further include iron ions.

The pullulan coating layer produced in the second step may be laminated on the iron ion-tannic acid coating layer.

The second step may include contacting a coating solution containing iron ions and an aqueous tannic acid solution to the coating target that has been subjected to the first step one or more times. The iron ion concentration in the coating solution may be freely changed within the range for the purpose of forming a coating film, for example, less than 1 mg/mL, less than 0.5 mg/mL, less than 0.3 mg/mL, 0.01 to 1 mg/mL, 0.01 to 0.5 mg/mL mL, 0.01 to 0.3 mg/mL, 0.05 to 1 mg/mL, 0.05 to 0.5 mg/mL, or 0.05 to 3 mg/mL, but is not limited thereto. When the iron ion concentration is 1 mg/mL or more, the iron ion-tannic acid coating layer formed on the pullulan coating layer may be formed too thinly, and a coating film at a level similar to that when iron ions are not added may be formed. There may be disadvantages of decreasing.

The concentration of pullulan in the coating solution may be freely changed within the range for the purpose of forming a coating film, for example, 1 mg/mL or more, 1.5 mg/mL or more, 2 mg/mL or more, 2.5 mg/mL or more, 1 to 10 mg/mL, 1.5 to 10 mg/mL, or 2 to 10 mg/mL, but is not limited thereto. When the concentration of pullulan in the coating solution is less than 1 mg/mL, the pullulan coating layer may not be sufficiently formed. . _{[Fe(III)-TA /Pul] n} coating was performed by changing the pullulan concentration in the pullulan coating solution to 1 mg/mL, 2.5 mg/mL, and 10 mg/mL in one embodiment, the pullulan concentration in the coating solution It was confirmed that there was no significant difference in the formation level of the coating film compared to the case where the pullulan concentration was 2.5 mg/mL even in the case of 10 mg/mL.

The coating method provided by the present invention may omit the step of chemically functionalizing pullulan. The chemical functionalization may be performed by, for example, one or more methods selected from the group consisting of anionic/cationic modification, hydrophobic modification, and grafting. The anionic/cationic modification is a method of attaching a negative or positively charged functional group to pullulan to give it an electric charge, and the hydrophobic modification is a method of attaching a hydrophobic material to pullulan to form a micelle structure, and the grafting is pullulan It refers to a method of continuously polymerizing monomers using a column as a backbone. By omitting the step of chemically functionalizing the pullulan, it is possible to prepare a coating film having an edible and biocompatible surface property by maintaining the inherent properties of pullulan.

In the coating method provided by the present invention, the first step and the second step may be repeated a single time or a plurality of times. The number of repetitions may be appropriately adjusted according to the thickness of the desired coating film, and according to the repetition of each step, the thickness of the coating film according to the layer-by-layer (LbL) can be adjusted.

In the coating method provided by the present invention, the pullulan coating layer may further include iron ions, and iron formed on the pullulan coating layer by adjusting the iron ion concentration in the coating solution for pullulan coating in the second step The thickness of the on-tannic acid coating layer can be adjusted.

In one example, the iron ion concentration in the pullulan coating solution of the second step is greater than 0 and less than 0.5 mg/mL, greater than 0 and less than 0.3 mg/mL, greater than 0 and less than 0.2 mg/mL, greater than or equal to 0.05 and less than 0.5 mg/mL, 0.05 to 0.3 mg/mL or 0.05 to 0.2 mg/mL, the thickness of the iron ion-tannic acid coating layer formed on the pullulan coating layer is 5 to 15 nm, 5 to 13 nm, 5 to 11 nm, 6 to 15 nm, 6 to 13 nm, 6 to 11 nm, 6.5 to 15 nm, 6.5 to 13 nm, or 6.5 to 11 nm, but is not limited thereto.

In one example, the iron ion concentration in the pullulan coating solution of the second step is 0.5 to 10 mg/mL, 0.5 to 5 mg/mL, 0.5 to 3 mg/mL, 0.5 to 2 mg/mL, or 0.5 to 1.5 mg/mL When , the iron ion formed on the pullulan coating layer - the thickness of the tannic acid coating layer is 1 to 5 nm, 1 to 4 nm, 1 to 3.5 nm, 2 to 5 nm, 2 to 4 nm, or 2 to 3.5 nm However, it is not limited thereto.

In one embodiment, the concentration of iron ions in the pullulan coating solution is adjusted to 0 mg/mL (not included), 0.1 mg/mL, or 1 mg/mL to prepare a coating film, and as a result of measuring the thickness of the coating film at each layer formation, When no iron ions were added (0 mg/mL) or when the iron ion concentration was 1 mg/mL, a very thin thin film was formed within about 2 nm of each pullulan coating layer, and the thickness of the iron ion-tannic acid coating layer The thickness of each coating layer was formed at an average level of 3 nm in FIG. When the iron ion concentration is 0.1 mg/mL, the thickness of the iron ion-tannic acid coating layer formed on the pullulan coating layer is 6 to 11 nm, and the iron ion concentration affects the formation of the iron ion-tannic acid coating layer and the pullulan coating layer. Insanity was confirmed.

The coating film provided by the present invention can be coated regardless of the coating target under mild conditions, the thickness can be adjusted at the nanometer level, is biocompatible, and has edible properties by maintaining the unique properties of pullulan. In addition, the coating film is environmentally friendly because it can decompose naturally.

1 is a schematic diagram showing a method of forming a coating film by sequentially stacking iron ion-tannic acid nano-coatings and pullulan nano-coatings.
2 is a graph of the thickness change of the coating film according to the number of layers of [Fe(III)-TA /Pul] _n , [Fe(III)-TA] _n and [Pul] _{n nanocoating films.}
3 is a graph showing a change in the thickness of the coating film according to the concentration of iron ions in the pullulan coating solution.
4 is a graph showing the change in thickness of the coating film according to the concentration of pullulan in the pullulan coating solution.
5 is a graph showing the results of surface element analysis of [Fe(III)-TA /Pul] _n , [Fe(III)-TA] _{n coating film.}
6 shows the results of measuring the contact angle of water on an uncoated gold substrate, [Fe(III)-TA /Pul] ₂ , and [Fe(III)-TA] _{4 coated gold substrate.}
7 is a result of measuring the contact angle of water before (Before) and after (After) exposing the iron ion-tannic acid coating film to BSA.
8 is a result of measuring the contact angle of water before (Before) and after (After) exposing the iron ion-tannic acid/pullulan coating film to BSA.
9 is an iron ion-tannic acid coating film ([Fe(III)-TA] ₄ ) and iron ion-tannic acid/pullulan coating film ([Fe(III)-TA/Pul] ₂ ) by reacting with hydrochloric acid of pH 2, respectively It is a graph as a result of checking the coating film thickness retention rate (Coating Remaining) according to the reaction time (Incubation Time).

Hereinafter, the contents of the present invention will be described in more detail by way of examples. However, the following examples are only for illustrating the present invention, and the scope of the present invention is not limited by the following examples.

Example 1. Coating method

1-1. Formation of iron ion-tannic acid coating layer

The gold plate to be coated is immersed in a piranha solution (3:1 (sulfuric acid: hydrogen peroxide volume ratio) mixture of sulfuric _{acid (H 2} SO ₄ ) and hydrogen peroxide (H ₂ O _{2 )) for 30 minutes to perform piranha work,} It was prepared by washing 3 times with distilled water.

For iron ion-tannic acid nano-coating, prepare tannic acid (TA) and FeCl ₃ .6H ₂ O to 40 mg/mL and 10 mg/mL in distilled water, respectively, and prepare the coating stock solution (tannic acid solution and iron ion solution, respectively). prepared.

The gold substrate after the piranha operation was placed in a petri dish and 4900uL of distilled water was added thereto. Next, 50 μL of the iron ion solution prepared above was added, and after 10 seconds, 50 μL of the tannic acid solution was added and shaken to mix well for 1 minute. After putting the gold plate in 5 ml of a 20 mM pH 7.4 Tris-HCl buffer solution for 3 minutes, the washing process was repeated 3 times with distilled water, and the remaining distilled water was removed with _{nitrogen (N 2 ) gas.} As a result, the gold plate was nano-coated in purple by the formation of an iron ion-tannic acid coating layer (Fe(III)-TA).

1-2. Formation of pullulan coating layer

To prepare a coating solution for pullulan coating, 12.5 mg/mL of pullulan and _{0.5 mg/mL of FeCl 3 .6H 2} O 0.5 mg/mL aqueous solution were prepared using distilled water, respectively. After that, 1 mL of pullulan aqueous solution (final concentration 2.5 mg/mL) and 1 mL of iron ion (FeCl ₃ 6H ₂ O) aqueous solution (final concentration 0.1 mg/mL) were added to a petri dish containing 3 mL of 50 mM pH 7.4 Tris-HCl buffer solution. After sequential addition, the mixture was shaken for 10 minutes to prepare a pullulan coating solution.

The pullulan has a structure of Formula 1 below.

[Formula 1]

In Example 1-1, the iron ion-tannic acid-coated gold plate (substrate) is put in a petri dish, 5 mL of the pullulan coating solution is added, shaken for 10 minutes, and the washing process is repeated 3 times with distilled water, The remaining distilled water was removed with nitrogen (N _{2 ) gas.} As a result, a transparent pullulan nanofilm was formed.

Example 2. Analysis of the thickness of the coating film

By repeating the coating layer forming process of Examples 1-1 to 1-2, it was confirmed whether the thickness was adjusted. For comparison, the thickness was measured while increasing the number ( _n ) of the [Fe(III)-TA] _n coating film or the [Pul] _{n coating film.}

The thickness measurement of the coating film was analyzed with a model to which the Cauchy equation was applied. Specifically, the thickness of the visible light region (300-700 nm) was obtained by applying the Cauchy model based on the results detected after being reflected and refracted on the surface of the nanofilm. It was measured using a spectroscopic ellipsometer (J. A. Woolam Co., USA).

2 and Table 1 below show the average thickness measurement result of each coating film according to the number of coating layers. In FIG. 2 and Table 1, when only the iron ion-tannic acid coating layer of Example 1-1 was laminated on the [Fe(III)-TA/Pul] _n coating film, it was indicated as "+ Fe(III)-TA".

coating film Average thickness (nm) coating film Average thickness (nm) coating film Average thickness (nm) [Fe(III)-TA] ₁ 3.51 [Fe(III)-TA] ₁ 3.19 [Pul] ₁ 2.15 [Fe(III)-TA/Pul] ₁ 5.87 [Fe(III)-TA] ₂ 5.5 [Pul] ₂ 1.9 [Fe(III)-TA/Pul] ₁ + Fe(III)-TA 16.76 [Fe(III)-TA] ₃ 9.73 [Pul] ₃ 2.16 [Fe(III)-TA/Pul] ₂ 20.03 [Fe(III)-TA] ₄ 12.47 [Pul] ₄ 2.38 [Fe(III)-TA/Pul] ₂ + Fe(III)-TA 30.91 [Fe(III)-TA] ₅ 18.99 [Pul] ₅ 2.15 [Fe(III)-TA/Pul] ₃ 34 [Fe(III)-TA] ₆ 21.84 [Pul] ₆ 2.67 [Fe(III)-TA/Pul] ₃ + Fe(III)-TA 40.93 [Fe(III)-TA] ₇ 23.77 [Pul] ₇ 2.56 [Fe(III)-TA/Pul] ₄ 41.61 [Fe(III)-TA] ₈ 26.36 [Pul] ₈ 1.99 [Fe(III)-TA/Pul] ₄ + Fe(III)-TA 51.18 [Fe(III)-TA] ₉ 28.06 [Pul] ₉ 2.26 [Fe(III)-TA/Pul] ₅ 52.34 [Fe(III)-TA] ₁₀ 31.23 [Pul] ₁₀ 2.28

The iron ion-tannic acid single coating layer had a thickness of 3.19 nm or 3.51 nm when the coating was performed once, and as the Fe(III)-TA coating layer was repeatedly laminated ([Fe(III)-TA] _n ), the thickness was linear. increased to _{On the other hand, in the case of the coating film ([Pul] n} ) in which only the pullulan coating layer (Pul) prepared by the method of Example 1-2 is laminated, an increase in thickness does not appear even if the coating is performed multiple times, multilayer thin film laminate (LbL) It was confirmed that it was not possible to control the thickness of the pullulan coating film in this way.

In the case of the [Fe(III)-TA/Pul] _n coating film, the Fe(III)-TA coating layer was formed to a thickness of 3.5 nm in the base layer in direct contact with the gold substrate to be coated, but Fe(III) formed on the pullulan coating layer )-TA coating layer showed a thickness of about 1.5 to 3.5 times that of the base layer, confirming that the pullulan coating layer affects the formation of the Fe(III)-TA coating layer. In addition, the pullulan coating layer in the [Fe(III)-TA/Pul] _n coating film is also formed at the level of 1 to 5 nm, and the thickness of the coating film having pullulan surface properties can be controlled at the nanometer level using the multi-layer thin film lamination method. was confirmed.

Comparative Example 1. Analysis of the thickness of the coating film according to the iron ion concentration in the pullulan coating solution

In order to confirm the effect of the iron ion concentration in the pullulan coating solution on the coating film formation, the [Fe(III)-TA/Pul] _n coating film was prepared by the method of Examples 1-1 to 1-2, but in the above Examples _{Gold plate coating was performed so that the final concentrations of iron ions (FeCl 3} .6H ₂ O) in the coating solution prepared in 1-2 were 0 mg/mL, 0.1 mg/mL, and 1 mg/mL, respectively.

Then, the thickness analysis of the coating layer according to the lamination step was performed in substantially the same manner as in Example 2. 3 and Table 2 below show the analysis results of the thickness change of each coating film according to the iron ion concentration in the pullulan coating solution.

coating film Coating thickness by iron ion concentration (nm) 0.1 mg/mL 1 mg/mL 0 mg/mL [Fe(III)-TA] ₁ 3.51 2.78 2.7 [Fe(III)-TA/Pul] ₁ 5.87 4.01 3.49 [Fe(III)-TA/Pul] ₁ + Fe(III)-TA 16.76 7.3 6.32 [Fe(III)-TA/Pul] ₂ 20.03 7.87 7.24 [Fe(III)-TA/Pul] ₂ + Fe(III)-TA 30.91 11.28 10.8 [Fe(III)-TA/Pul] ₃ 34 12.2 13.07 [Fe(III)-TA/Pul] ₃ + Fe(III)-TA 40.93 14.49 15.69 [Fe(III)-TA/Pul] ₄ 41.61 14.69 17.33 [Fe(III)-TA/Pul] ₄ + Fe(III)-TA 51.18 18.25 19.99 [Fe(III)-TA/Pul] ₅ 52.34 18.73 22

When no iron ions were added (0 mg/mL) or when the iron ion concentration was 1 mg/mL, a very thin thin film was formed within 2 nm of each pullulan coating layer, and the thickness of the iron ion-tannic acid coating layer was also The thickness of the coating layer was formed at an average level of 3 nm.

When the iron ion concentration is 0.1 mg/mL, the thickness of the iron ion-tannic acid coating layer formed on the pullulan coating layer is 6 to 11 nm, and the iron ion concentration affects the formation of the iron ion-tannic acid coating layer and the pullulan coating layer. Insanity was confirmed.

A complex having two or more central atoms such as a metal is called a polynuclear complex, and it is known that an _{aqueous solution of iron chloride (FeCl 3} ) containing Fe(III) is hydrolyzed to form Fe(OH) _{3 or FeOOH.} They form an oligomeric structure to achieve a thermodynamically stable structure in an aqueous solution, and then form multinuclear complex nanoparticles with pullulan, which is expected to affect the formation of the pullulan coating layer and the iron ion-tannic acid coating layer.

Comparative Example 2. Analysis of the thickness of the coating film according to the concentration of pullulan in the pullulan coating solution

In order to confirm the effect of the concentration of pullulan in the coating solution on the coating film formation, a gold substrate (Bare) coating was performed in substantially the same manner as in Examples 1-1 to 1-2, but in Example 1-2, the coating solution The final iron ion concentration was maintained at 0.1 mg/mL, and the prepared coating solution was used so that the pullulan concentration (final concentration) was 1 mg/mL, 2.5 mg/mL, and 10 mg/mL, respectively. Then, the thickness of the formed coating film was checked in the same manner as in Example 2 according to the number of laminations.

The change in the thickness of the coating film according to the lamination of each coating layer is shown in FIG. 4 and Table 3 below. In Table 3 below, the coating film thickness was expressed in nm, and the nm unit was omitted.

Pullulan Concentration [Fe(III)-TA] ₁ [Fe(III)-TA/Pul] ₁ [Fe(III)-TA/Pul] ₁ + Fe(III)-TA [Fe(III)-TA/Pul] ₂ [Fe(III)-TA/Pul] ₂ + Fe(III)-TA [Fe(III)-TA/Pul] ₃ 1 mg/mL 3.14 5.59 14.58 18.11 25.99 28.65 2.5 mg/mL 3.14 5.20 16.76 20.03 30.91 34.00 10 mg/mL 3.14 5.45 18.26 19.88 31.53 32.39

The thickness of the Fe(III)-TA coating layer formed on the pullulan layer was 2 to 4 nm thicker when the pullulan concentration in the final coating solution was 2.5 mg/mL than when the pullulan concentration was 1 mg/mL, but the pullulan concentration was 2.5 mg At /mL and 10mg/mL, no significant change in the thickness of the Fe(III)-TA layer was observed. Therefore, in the subsequent experiment, the coating was performed by preparing the pullulan concentration in the pullulan coating solution to be 2.5 mg/mL.

Example 3. Analysis of the surface composition of the coating film

_{[Fe(III)-TA/Pul] 2} coating film prepared by repeating the method of Examples 1-1 to 1-2 twice _{and [Fe(III)-TA] 4} coating film prepared without a pullulan coating layer as a control The surface element composition was analyzed by X-ray photoelectron spectroscopy (XPS).

The [Fe(III)-TA/Pul] ₂ coating film and the [Fe(III)-TA] ₄ coating film were prepared by controlling the number of laminations so that the thickness of each coating film was similar. It is known that the C/O ratio of the tannic acid (C ₇₆ H ₅₂ O ₄₆ ) molecule is 1.65 and the C/O ratio of the pullulan molecule (C ₆ H ₁₂ O ₅ ) _n is 1.2.

Figure 5 shows the C/O ratio analysis result of each coating film and Table 4 below.

coating film C 1s O 1s C/O ratio [Fe(III)-TA] ₄ 60.99% 36.66% 1.66 [Fe(III)-TA/Pul] ₂ 56.59% 41.41% 1.37

[Fe(III)-TA] ₄ The C/O ratio of the coating film was 1.66, which was similar to the known C/O ratio of tannic acid molecules, and in the case of pullulan film, the C/O ratio of the surface was It was confirmed that it was distinguished from the Fe(III)-TA layer at a level of 1.37 and exhibited a value similar to the C/O ratio of the pullulan molecule.

While the pullulan coating layer is formed very thin at the level of 1 to 2 nm, X-ray Photoelectron Spectroscopy (XPS) equipment measures about 5 nm of the coated surface. Therefore, some elements included in the iron ion-tannic acid coating layer that exist under the pullulan coating layer are also measured. It is assumed to be measured as

Therefore, it was experimentally confirmed that the pullulan coating layer was successfully formed on the surface of the coating film prepared by performing the method of Examples 1-1 to 1-2.

Example 4. Analysis of the surface properties of the coating film using the contact angle of water

[Fe(III)-TA/Pul] _{2 In} order to confirm the surface properties of the coating film, an uncoated gold plate (Bare), a [Fe(III)-TA] ₄ coating film that does not contain a pullulan coating layer, and [Fe(III) )-TA/Pul] ₂ The water contact angles of the coating films were compared respectively.

Specifically, the measurement of the contact angle of water was performed by measuring the angle between the surface-droplet produced by dropping a 10 μm water droplet onto the nanofilm, and the results are shown in Tables 5 and 6 below.

coating film Water contact angle (°) Control (Bare) 65.9±0.6 [Fe(III)-TA] ₄ 22.7±0.4 [Fe(III)-TA/Pul] ₂ ≤5

The uncoated gold plate showed a water contact angle of more than 60°, but after Fe(III)-TA coating, the water contact angle was about 22.7° and had somewhat hydrophilic properties. )-TA/Pul after coating, it was confirmed that the water contact angle was less than 5° and thus had super hydrophobic properties. The pullulan molecule is expected to have super hydrophobic surface properties due to the presence of a large number of hydroxyl groups in the pullulan molecule. It is demonstrated that the coating method provided by the present invention can successfully form a nanofilm having the surface properties of pullulan.

Example 5. Confirmation of antifouling properties of pullulan coating through measurement of water contact angle

Example 1-1 to a method of manufacturing the 1-2 [Fe (Ⅲ) -TA / Pul] as the _first coating film and the control of pullulan for the [Fe (Ⅲ) -TA] ₁ coating film prepared without a coating layer, pullulans To check the antifouling effect of the egg coating layer, it was added to 1 mg/ml of BSA (bovine serum albumin) for 5 minutes and shaken, then the water contact angle was measured. The measurement of the contact angle of water was performed in substantially the same manner as in Example 4, and the results are shown in Table 6 and FIGS. 7 to 8 below. In Figure 7, [Fe(III)-TA] ₁ The albumin reaction of the coating film before (Befor) and after (After) water contact angle measurement results, in Figure 8 [Fe (III)-TA / Pul] ₁ The albumin reaction of the coating film The water contact angle measurement results before (Befor) and after (After) are shown.

coating film Contact angle of water before contamination (°) Contact angle of water after contamination (°) [Fe(III)-TA] ₁ 25.0 57.8 [Fe(III)-TA/Pul] ₁ ≤5 ≤5

The water contact angle of the iron ion-tannic acid coating film without pullulan nano-coating increased from 25° before contact with the BSA solution to about 60° after contact, but when pullulan coating was performed on the iron ion-tannic acid coating film, the water contact angle was kept below 5 degrees. Through this, it can be seen that the pullulan coating film has antifouling properties that prevent proteins or organic matter including BSA from adhering to the surface.

Example 6. Confirmation of acid resistance of the coating film in acidic conditions

_{A [Fe(III)-TA/Pul] 2} coating film was formed on a gold substrate by the method of Examples 1-1 to 1-2, and as a control, a [Fe(III)-TA] ₄ coating prepared without a pullulan coating layer A gold substrate was prepared, and each gold substrate was immersed in a 10 mM HCl aqueous solution (pH 2) to measure the rate of decrease in the thickness of the coating film over time.

Specifically, when the reaction time with the aqueous hydrochloric acid solution is 5 minutes, 10 minutes, 30 minutes, 60 minutes, 120 minutes and 1 day, each substrate is taken out, washed three times with tertiary distilled water, and then dried with nitrogen (N ₂ ) gas, The thickness of the coating film was measured in substantially the same manner as in Example 2-1. The thickness retention (Coating Remaining, %) of the coating film was calculated by the method of Equation 1 below.

[Equation 1]

Coating Remaining(%)=(Coating film thickness after reaction/Coating film thickness before reaction)*100

9 shows a graph of the retention rate (%) of the coating film thickness according to the hydrochloric acid reaction time of each substrate. The thickness of the [Fe(III)-TA] ₄ coated substrate was reduced to 40% of the pre-reaction thickness in less than 5 minutes under acidic conditions, but the [Fe(III)-TA/Pul] ₂ coated substrate had no coating film. It decomposed more slowly and reached 40% of the pre-reaction thickness after one day of reaction with hydrochloric acid. Through this, it can be seen that the [Fe(III)-TA/Pul] coating film has the advantage of high resistance to acidic environment compared to the control.

hydrochloric acid reaction time 0min 5min 10min 30min 60min 120min 1 day [Fe(III)-TA] ₄ Coating film thickness retention rate (%) 100 44.23 42.22 40.53 37.28 38.79 32.85 [Fe(III)-TA/Pul] ₂ Coating thickness retention rate (%) 100 83.73 73.45 61.70 56.27 50.93 40.55

Claims (11)

an iron ion-tannic acid coating layer comprising iron ions and tannic acid; and
The iron ion is laminated on the tannic acid coating layer, comprising a pullulan coating layer comprising pullulan, the coating film. The coating film according to claim 1, wherein the unit coating layer consisting of the iron ion-tannic acid coating layer and the iron ion-tannic acid coating layer laminated on the pullulan coating layer is laminated a plurality of times. The coating film according to claim 1, wherein the coating film has a water contact angle of 0 to 10°. A coating agent for food, comprising the coating film of any one of claims 1 to 3. The coating agent for food according to claim 4, wherein the coating film is an edible coating film. A coating agent for pharmaceuticals, comprising the coating film of any one of claims 1 to 3. to the coating
A first step of forming an iron ion-tannic acid coating layer containing iron ions and tannic acid;
A coating method comprising a second step of forming a pullulan coating layer comprising pullulan on the iron ion-tannic acid coating layer. The method of claim 7, wherein the coating target is a food or drug. The coating method according to claim 7, wherein the first to second steps are repeatedly performed. The method of claim 7, wherein the first to second steps include contacting the coating solution with the coating object; and washing and drying the coating object in contact with the coating solution. 11. The method of claim 10,
(1) the iron ion concentration in the coating solution of the second step is greater than 0 and less than 0.5 mg/mL, and the iron ion produced in the first step performed after the second step has a thickness of 5 to 15 nm; or
(2) the iron ion concentration in the coating solution of the second step is 0.5 mg/mL to 10 mg/mL, and the iron ion-tannic acid coating layer produced in the first step performed after the second step has a thickness of 1 to 5 nm the way it is.

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