Body fluid-absorbing antibacterial fiber, fiber structure including said fiber, and wound dressing

Abstract

[Problem] Absorbent fibers comprising a polyacrylate or an alginate have been proposed as an absorbent material for wound dressings in recent years. In wound dressings comprising the absorbent fibers, absorption of body fluids such as blood and exudate does not cause gel detachment, and air permeability is excellent, but such air permeability makes it difficult to block bacterial invasion. Therefore, the wound dressings have been required to have the function of preventing bacterial proliferation, but it has been difficult to achieve both body fluid absorbency and the function of preventing bacterial proliferation. [Solution] A body fluid-absorbing antibacterial fiber containing 1.0-5.0 mmol / g of an acidic carboxyl group, wherein the absorption ratio for a pseudo body fluid is 5.0-25.0 times, and the pH of the surface of the fiber having absorbed the pseudo body fluid is 4.5-6.5.

Description

Humid-absorbing antibacterial fiber, fiber structure containing the fiber, and wound dressing

[0001] The present invention relates to a humid-absorbing antibacterial fiber having a function of absorbing body fluids and a function of suppressing the growth of bacteria, and a fiber structure containing the same.

[0002] Conventionally, gauze, powder agents, spray agents, ointments, creams, sponge agents, etc. have been used as treatment materials for wound surfaces and bedsore surfaces. Most of these are for drying and healing the wound site by absorbing exudate from the wound surface. However, in recent years, it has been found that maintaining the exudate on the wound surface rather than drying the wound site and keeping it in an appropriate moist environment can promote wound healing, and the necessity of maintaining the wound site in an appropriate moist environment (so-called moist therapy) has been recognized, and wound dressings suitable for this have been developed.

[0003] Requirements for this wound dressing include absorbency, moisture retention, prevention of bacterial invasion, prevention of bacterial growth, mechanical strength, etc. Conventionally, water-absorbing gels have been used as constituent materials for absorbing and maintaining the moisture of this wound dressing. As this water-absorbing gel, hydrocolloids, PVA hydrogels, alginate gels, sodium polyacrylate salt gels, etc. are known.

[0004] Hydrocolloids absorb exudate by swelling of hydrophilic colloid particles contained in a hydrophobic base material, so they are excellent in absorbency, but have the drawback that gel-like substances tend to remain on the wound surface during replacement. In addition, PVA hydrogels have the advantage that no gel-like substances remain on the wound surface because they have a film shape, but they have the drawback that because they cover with a film that is not breathable outside the wound surface, they become stuffy and are prone to sweating and itching.

[0005] To address these drawbacks, absorbable fibers made of alginate or polyacrylate have been proposed. Because of their fibrous structure, the gel is less likely to detach, and these materials enable the creation of breathable wound dressings. However, breathability means that the wound dressing is an open system, making it difficult to prevent bacterial invasion. Therefore, it is desirable that such wound dressings also possess a function to prevent bacterial growth.

[0006] Patent Document 1 discloses a method for imparting antibacterial properties to absorbent fibers by spraying them with silver and silver nitrate, which are antibacterial agents. However, silver and silver compounds are very expensive and unsuitable as general-purpose materials. Furthermore, the spray application method has the problem of making it difficult to uniformly apply the antibacterial agents silver and silver nitrate, resulting in areas where antibacterial properties cannot be exhibited.

[0007] Incidentally, it is known that bacteria such as Staphylococcus aureus have difficulty growing in low pH environments. In addition, in low pH environments, the binding force between hemoglobin in the blood and oxygen decreases (known as the Bohr effect), and more oxygen is supplied to fibroblasts, etc., thereby promoting wound healing. For this reason, it is preferable to keep the pH near the wound surface slightly acidic. In this regard, Patent Document 2 discloses a wound dressing consisting of a mixture of glass fibers having an eluting antibacterial component and absorbent fibers having an acidic functional group. According to this document, when the wound dressing comes into contact with blood or exudate, the antibacterial component elutes and exhibits antibacterial properties, and protons are released from the acidic functional group of the absorbent fiber, thereby suppressing the rise in pH caused by the elution of the alkaline antibacterial component. However, because glass fibers with low absorbency are an essential component, there are limitations on the blending of absorbent fibers, which has the drawback of reducing the absorbent performance of the wound dressing. Furthermore, since the protons released from the absorbent fibers are consumed in neutralizing the alkaline antibacterial components eluted from the glass fibers, it was difficult to effectively obtain the bacterial growth inhibitory effect and healing promotion effect in the low pH environment described above.

[0008] International Publication No. WO2009 / 115804, Japanese Patent Publication No. 2018-029643

[0009] The present invention has been made in view of the above circumstances, and its purpose is to provide a body fluid-absorbing antibacterial fiber and its fiber structure that have high absorption performance for body fluids without adding or mixing an antibacterial agent to the absorbent fiber.

[0010] As a result of diligent research to achieve the above-mentioned objectives, the inventors discovered that a material containing an acidic carboxyl group possesses not only antibacterial properties but also the ability to absorb bodily fluids, leading to the present invention.

[0011] In other words, the present invention is achieved by the following means: (1) A body fluid-absorbing antibacterial fiber characterized by containing 1.0 to 5.0 mmol / g of acid-type carboxyl groups, having an absorption ratio of 5.0 to 25.0 times for simulated body fluids, and having a pH of 4.5 to 6.5 on the fiber surface when it has absorbed simulated body fluids. (2) The body fluid-absorbing antibacterial fiber according to (1), characterized by being a core-sheath fiber consisting of a sheath having an acid-type carboxyl group-containing polymer and a core having an acrylonitrile polymer. (3) A fiber structure containing 5 to 100% by weight of the body fluid-absorbing antibacterial fiber according to (1) or (2). (4) A wound dressing characterized by having the fiber structure according to (3) arranged in a pad portion.

[0012] The bodily fluid-absorbing antibacterial fiber of the present invention, when in contact with bodily fluids, contains an acidic carboxyl group in the bodily fluids. ３ The carboxyl groups are neutralized by buffering agents and converted to salt-type carboxyl groups, thereby exhibiting fluid absorption properties. On the other hand, the protons released from the acid-type carboxyl groups cause the pH of the fiber surface to become slightly acidic to weakly acidic, exhibiting antibacterial properties. In other words, it is possible to provide a fiber that possesses both fluid absorption and antibacterial properties without the use of antibacterial agents. Such fibers can be suitably used, for example, as wound dressings or pressure ulcer dressings.

[0013] The body fluid absorbent antibacterial fiber of the present invention is a fiber containing 1.0 to 5.0 mmol / g, preferably 2.0 to 3.5 mmol / g, of acidic carboxyl groups. If the amount of acidic carboxyl groups in the fiber is less than 1.0 mmol / g, the amount of NaHCO3 in body fluids is less than 1.0 mmol / g. ３Neutralization with buffering components such as the above may result in an insufficient amount of salt-type carboxyl groups, and the amount of proton release necessary for antibacterial activity may also be insufficient, potentially leading to inadequate body fluid absorption and antibacterial activity. On the other hand, if the amount of acid-type carboxyl groups exceeds 5.0 mmol / g, the fiber properties in the dry state become brittle, and there is a risk that the fibers may break or fall off when wound dressings are made using these fibers. In this invention, the acid-type carboxyl group refers to a carboxyl group "-COOH" whose counterion is a hydrogen ion, and the hydrogen ion of the acid-type carboxyl group is K ＋ Na ＋ Mg ２＋ Ca ２＋ A carboxyl group that is replaced by another ion, such as the one mentioned above, is called a salt-type carboxyl group. In this invention, body fluid refers to liquids that an organism has inside its body or that are expelled from the body, and examples include blood and exudate.

[0014] The bodily fluid-absorbing antibacterial fiber of the present invention has an absorption ratio of 5.0 to 25.0 times, preferably 10.0 to 25.0 times, for a simulated bodily fluid described later. This fiber is a suitable material for moist wound healing. If the ratio is less than 5.0 times, the objective of keeping the wound surface moist, which is required for moist wound healing, cannot be achieved. If the ratio exceeds 25.0 times, the breathability obtained by the fiber shape cannot be ensured.

[0015] The body fluid-absorbing antibacterial fiber of the present invention is a fiber whose surface pH after absorption of simulated body fluid is in the range of 4.5 to 6.5. A lower pH is preferable for exhibiting antibacterial properties after absorption of simulated body fluid. Sufficient antibacterial properties cannot be obtained at a pH of 6.5 or higher. On the other hand, with the aforementioned upper limit of 5.0 mmol / g for the amount of acid-type carboxyl groups, it is difficult and impractical to keep the pH below 4.5. In moist wound healing, the gel after absorption of body fluid is in direct contact with the wound surface, and it is most preferable for the surface of the gel after absorption of body fluid to exhibit antibacterial properties. Therefore, the present invention specifies the pH of the fiber surface after absorption of simulated body fluid. Furthermore, the body fluid-absorbing antibacterial fiber may contain salt-type carboxyl groups, and the amount is not particularly limited as long as the pH of the surface of the body fluid-absorbing antibacterial fiber after absorption of simulated body fluid is in the range of 4.5 to 6.5.

[0016] The bodily fluid-absorbing antibacterial fiber of the present invention is not particularly limited as long as it can pass through general fiber processing processes such as nonwoven fabric processing when dry and has gel properties that allow it to maintain its fiber form when absorbing bodily fluids. For example, a core-sheath fiber having a two-layer structure called a core-sheath structure, which consists of a non-gelling core region and a gelling sheath region, is suitable because it has high wet fiber properties when it absorbs bodily fluids and gels, and is less prone to gel shedding.

[0017] One form of a body fluid-absorbing antibacterial fiber having a core-sheath structure is a core-sheath composite fiber comprising a sheath portion having an acid-type carboxyl group-containing polymer and a core portion having an acrylonitrile-based polymer. As such a core-sheath composite fiber, for example, as described in Japanese Patent Application Publication No. 2023-67820, a core-sheath structure composite fiber can be used, which is produced by crosslinking the fiber surface of an acrylonitrile-based fiber with a hydrazine-based compound and then performing a hydrolysis reaction with an aqueous sodium hydroxide solution. In this case, it is necessary to immerse the core-sheath structure composite fiber in an aqueous hydrochloric acid solution to convert the salt-type carboxyl groups to acid-type carboxyl groups.

[0018] The form of the fibrous structure containing the body fluid-absorbing antibacterial fibers of the present invention is not particularly limited, and can be appropriately selected from nonwoven fabrics, woven fabrics, knitted fabrics, paper sheets, etc. For example, a sheet form makes it easier to apply to wound dressings and pressure ulcer dressings for moist wound healing. It can also be used as a packing material in its unprocessed state. Here, the content of the body fluid-absorbing antibacterial fibers in the fibrous structure is preferably 5 to 100% by weight, more preferably 50 to 100% by weight, and even more preferably 70 to 100% by weight. If the content is less than 5% by weight, there is a risk that the body fluid absorption performance and antibacterial performance will be insufficient.

[0019] When processing into a sheet-like form, it is preferable to combine it with other fiber materials to form nonwoven fabrics, woven fabrics, knitted fabrics, paper, etc., according to conventionally known methods. Here, the other fiber materials are not particularly limited as long as they do not increase the pH of the fiber surface of the bodily fluid-absorbing antibacterial fiber of the present invention, such as having basic functional groups such as amino groups or containing alkaline components such as CaO. Natural fibers, organic fibers, semi-synthetic fibers, and synthetic fibers can be used, and inorganic fibers may also be used depending on the application. Specific examples include cotton, linen, silk, wool, nylon, rayon, polyester, and acrylic fibers.

[0020] When using the aforementioned fibrous structure containing the body fluid-absorbing antibacterial fibers as a wound dressing or pressure ulcer dressing, it is preferable to use it in the pad portion of a general wound dressing or pressure ulcer dressing. This is because it fulfills the purpose of absorbing body fluids from the wound or healing site and maintaining a moist state.

[0021] <Measurement of Acid-Type Carboxyl Groups> Approximately 1 g of a thoroughly dried sample was accurately weighed (W1 [g]), and 200 ml of water was added to it. A titration curve was obtained using a 0.1 mol / l sodium hydroxide aqueous solution according to a conventional method. From the titration curve, the amount of sodium hydroxide aqueous solution consumed by the acid-type carboxyl groups (V1 [ml]) was determined, and the amount of acid-type carboxyl groups was calculated using the following formula: Amount of acid-type carboxyl groups [mol / g] = 0.1 × V1 / W1

[0022] <Method for preparing simulated body fluid> Add 6.3g of sodium chloride and 2.3g of sodium bicarbonate to 1000g of distilled water, stir, and dissolve to use as the simulated body fluid.

[0023] <Method for Measuring the Absorption Ratio of Simulated Body Fluid> Approximately 1 g of a thoroughly dried sample is accurately weighed (A1 [g]), and 100 g of simulated body fluid is added to it and left to stand for 30 minutes. The sample after standing is placed in a 200-mesh nylon bag, and after adjusting the centrifugal force to 80 G in a centrifugal dehydrator, it is dehydrated for 5 minutes. The weight of the sample after centrifugal dehydration is measured (B1 [g]), and the absorption ratio of simulated body fluid is calculated using the following formula: Absorption ratio of simulated body fluid [g / g] = (B1 - A1) / A1 - 1

[0024] <Method for measuring the pH of the fiber surface after absorbing simulated body fluid> The surface pH of the sample in a wet state after measuring the absorption ratio of simulated body fluid was measured using a surface pH meter (manufactured by Satotech Co., Ltd.).

[0025] <Antibacterial Activity Measurement Method> Bacteria cultured at 37°C for approximately 20 hours were suspended in sterile physiological saline. The wavelength of the spectrophotometer was set to 630 nm and the optical density was adjusted to approximately 0.12. Then, the sample was diluted approximately 100 times with 1 / 2 nutrient medium to prepare the test bacterial solution. Sterilized vials (30 ml capacity) were thoroughly sprayed with disinfectant ethanol beforehand, and 0.4 g of each test sample, dried in a safety cabinet, was added to the bottom of each vial. After adding 0.2 ml of the test bacterial solution to each vial, they were cultured at 37°C for 18 hours. Immediately after culturing and after 18 hours at 37°C, 20 ml of buffered physiological saline was added to each vial and shaken vigorously 30 times (100-fold dilution). １ from 10 ５ The solution was diluted 1:1. One ml each of the stock solution and each diluted solution was added to two sterile plastic petri dishes, and approximately 20 ml of nutrient agar medium, which had been kept warm at approximately 50°C after sterilization, was added to dilute it. After cooling and incubation at 37°C for approximately 48 hours, the number of bacteria that appeared was measured, and the bacterial growth value was calculated using the following formula: Bacterial growth value = LOG(number of bacteria after incubation) - LOG(number of bacteria before incubation). A positive bacterial growth value indicates that the bacteria have grown, and a negative value indicates that the bacteria have decreased. When considering the practical application of the present invention, in order to obtain sufficient antibacterial activity, it is preferable that the bacterial growth value be -1 or less, and more preferably -2 or less.

[0026] <Example 1> An acrylic fiber A was obtained by dissolving 10 parts of an acrylonitrile polymer consisting of 90% acrylonitrile and 10% methyl acrylate in 90 parts of a 48% sodium rhodane aqueous solution. The resulting spinning stock was spun, drawn, and dried according to a conventional method.

[0027] Acrylic fiber A was immersed in a 1.1% hydrazine aqueous solution and subjected to a cross-linking structure introduction treatment at 85°C for 40 minutes. Next, an amount equal to the weight of the fiber was applied to a 35% sodium hydroxide aqueous solution, and after application, a hydrolysis treatment was performed at 113°C for 9 minutes. This yielded core-sheath structure fiber A' having salt-type carboxyl groups in the sheath portion.

[0028] Core-sheath structure fiber A' having salt-type carboxyl groups was dispersed in water, and a 5% sulfuric acid aqueous solution was added until the pH reached 2.3. After pH adjustment, the sample was washed with water to remove impurities. Subsequently, it was dried in an 80°C dryer to obtain core-sheath structure fiber A'' having acid-type carboxyl groups. The results of evaluating this sample are shown in Table 1. Staphylococcus aureus was used to measure the antibacterial performance.

[0029] <Example 2> Table 1 shows the evaluation results of a sample prepared in the same manner as in Example 1, except that the hydrolysis treatment conditions were changed to 113°C for 4 minutes.

[0030] <Example 3> The evaluation results of a sample prepared in the same manner as in Example 1, except that the hydrolysis conditions were changed to 113°C × 20 minutes, are shown in Table 1.

[0031] <Comparative Example 1> Table 1 shows the evaluation results of a sample obtained by neutralizing the core-sheath structure fiber A'' having acid-type carboxyl groups from Example 1 with ammonia gas to convert it to salt-type carboxyl groups.

[0032] <Comparative Example 2> The results of evaluating the acrylic fiber A of Example 1 are shown in Table 1.

[0033] <Comparative Example 3> The results of evaluating commercially available polyester fibers are shown in Table 1.

[0034] <Comparative Example 4> Table 1 shows the evaluation results of a sample prepared in the same manner as in Example 1, except that the hydrolysis conditions were changed to 113°C × 1 minute.

[0035] <Comparative Example 5> Table 1 shows the evaluation results of a sample prepared in the same manner as in Example 1, except that the hydrolysis conditions were changed to 113°C x 40 minutes. The sample was very brittle and could not be extracted in fibrous form.

[0036]

[0037] As can be seen from Table 1, each embodiment of the present invention exhibits good pseudo-body fluid absorption performance and antibacterial properties, making it useful as an absorbent material for moist wound healing. On the other hand, as shown in Comparative Example 1, antibacterial properties are not exhibited with salt-type carboxyl groups. Comparative Examples 2 and 3, which do not have carboxyl groups, do not exhibit sufficient pseudo-body fluid absorption performance or antibacterial properties. Similarly, Comparative Example 4, which lacks acid-type carboxyl groups, also lacks sufficient pseudo-body fluid absorption performance and antibacterial properties. Comparative Example 5, which has many acid-type carboxyl groups, is very brittle as a fiber, making it difficult to maintain its fiber shape and impossible to process into a breathable fiber.

Claims

1. A body fluid-absorbing antibacterial fiber characterized by containing 1.0 to 5.0 mmol / g of acid-type carboxyl groups, having an absorption ratio of 5.0 to 25.0 times for simulated body fluids, and having a pH of 4.5 to 6.5 on the fiber surface when it has absorbed simulated body fluids.

2. The bodily fluid-absorbing antibacterial fiber according to claim 1, characterized in that it is a core-sheath fiber comprising a sheath portion having an acid-type carboxyl group-containing polymer and a core portion having an acrylonitrile-based polymer.

3. A fiber structure containing 5 to 100% by weight of the body fluid-absorbing antibacterial fiber described in claim 1 or 2.

4. A wound dressing characterized in that the fibrous structure described in claim 3 is arranged in the pad portion.

Images