Cellulose Fiber

Abstract

The present disclosure provides a method of producing a solution of polymer-coated metal nanoparticles comprising mixing a first alkaline aqueous solution with an aqueous polymer solution to form an alkaline aqueous polymer solution, and mixing with an aqueous solution of a metal salt to form a solution of polymer-coated metal nanoparticles.A further method of producing cellulose fibers impregnated with metal nanoparticles comprises swelling the fibers and mixing the fibers with the solution of polymer-coated metal nanoparticles.

Description

[Technical field]

[0001] The present invention relates to a method for producing metal nanoparticles and impregnating them into cellulose fibers.The invention further relates to the fibers produced thereby, and to materials and fabrics comprising said fibers. [Background technology]

[0002] Fibers useful as components of advanced wound care dressings are known in the art, particularly fibers based on cellulose or cellulose derivatives such as carboxymethylcellulose (CMC), cellulose ethylsulfonate (CES) and their salts. For example, the commercial dressing AQUACEL® (sold by ConvaTec Inc., Skillman, NJ, USA) is based on carboxymethylcellulose. The commercial dressing DURAFIBER® (sold by Smith and Nephew, Hull, UK) is made from a mixture of cellulose fibers (TENCEL®) and CES fibers.

[0003] Metals such as silver, copper, zinc and mercury are known to have antibacterial properties. Due in part to the emergence of antibiotic-resistant bacteria, there has been renewed interest in the use of metallic silver as an antibacterial agent, particularly in wound dressings. Metallic silver is a broad-spectrum antibiotic that has proven effective against such resistant bacteria. Current research suggests that metallic silver, due to its mechanism of action, does not allow the development of bacterial resistance. WO 2015 / 040435, by the applicant, describes a method for preparing cellulose fibres impregnated with metal nanoparticles.

[0004] Currently available wound dressings on the market contain silver mainly in ionic form, i.e. as salts or other compounds. However, due to the solubility of silver salts or compounds in the aqueous nature of the wound environment, the antimicrobial properties of these dressings may be short-lived, leading to their almost instantaneous and complete release from the dressing. The rapid release of silver ions into the wound may cause toxic effects on the bacteria as well as the host cells. It has been reported that some silver salts can irritate the skin around the wound and that prolonged contact can cause localized argentation, a permanent grey-blue staining of the skin. Generally, silver salts are very sensitive to light and show rapid and extensive discolouration (turning brown or black), resulting in less than attractive visual properties.

[0005] One problem with existing attempts to solve the above problems is scalability. While some processes are effective for small-scale production of fibers, scaling up some processes results in reduced efficiency and increased costs. It is an object of the present invention to alleviate at least some of the above problems. Summary of the Invention

[0006] According to a first aspect of the present invention, there is provided a method of producing a solution of polymer-coated metal nanoparticles. The method may include mixing a first alkaline aqueous solution with an aqueous polymer solution to form an alkaline aqueous polymer solution. The method may include mixing the alkaline aqueous polymer solution with an aqueous solution of a metal salt to form a solution of polymer-coated metal nanoparticles.

[0007] As used herein, the term "metal nanoparticles" means particles of elemental metal having an average (ie, arithmetic mean) diameter of 100 nm or less.

[0008] The first alkaline aqueous solution may be a mixture of a group I hydroxide (e.g., sodium hydroxide or potassium hydroxide), a group I carbonate (e.g., Na 2 CO 3 or K 2 CO 3), Group I bicarbonates (e.g., NaHCO 3 or KHCO 3 ), tetraalkylammonium hydroxide (e.g., tetraethylammonium hydroxide), or mixtures thereof. In a preferred set of embodiments, the first aqueous solution includes sodium hydroxide and sodium carbonate.

[0009] 10. The method of any one of the preceding claims, wherein the metal salt comprises a metal selected from the group consisting of silver, copper, zinc, selenium, gold, cobalt, nickel, zirconium, molybdenum, gallium, iron, or any combination thereof, and in a preferred set of embodiments the metal is silver.

[0010] The metal salt may be a nitrate, acetate, carbonate, bicarbonate, sulfate, or mixtures thereof. In a preferred set of embodiments, the metal salt is a nitrate. In a preferred set of embodiments, the metal salt is silver nitrate.

[0011] The polymer may be selected from the group consisting of polyamide, polyimide, polyethyleneimine, polyvinyl alcohol, pectin, albumin, gelatin, carrageenan, gum, cellulose or its derivatives, poly(N-vinylpyrrolidone), poly(N-vinylcaprolactam) and mixtures thereof. For example, the gum may be xanthan, guar, arabic, acacia, etc. For example, the cellulose derivative may be hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, hydroxypropylmethylcellulose, etc. In a set of preferred embodiments, the polymer is poly(N-vinylpyrrolidone). Poly(N-vinylpyrrolidone) is also known as povidone, polyvidone, or PVP.

[0012] The polymers have a weight average molecular weight (M) of 8 to 360 kg / mol, or 20 to 80 kg / mol. w The polymer may have an M of greater than 10, 15, 20, 25, 30, 32, 34, 36, 38 or 40 kg / mol. wThe polymer may have an M of less than 360, 300, 250, 200, 150, 100, 80, 70, 60, 50, 45, 40, 38, 36, 34, 32 or 30 kg / mol. w In one series of embodiments, the polymer may have a weight average molecular weight (M) of 25 to 45 kg / mol, 30 to 40 kg / mol, 32 to 38, or 34 to 36 kg / mol. w ).

[0013] For example, in one set of embodiments, the polymer is poly(N-vinylpyrrolidone), and the polymer has a weight average molecular weight (M w ).

[0014] In one set of embodiments, a solution of polymer-coated metal nanoparticles can be obtained in the absence of an additional reducing agent.

[0015] In step (b), the mixing may be carried out at a temperature between 20° C. and 120° C. For example, the temperature may be at least 20, 30, 40, 50, 60, 70, 80, 90, 100 or 110° C. The temperature may be less than 110° C., 100° C., 90° C., 80° C., 70° C., 60° C., 50° C., 40° C. or 30° C. In a preferred set of embodiments, the temperature is between 60° C. and 100° C.

[0016] According to a second aspect of the present invention there is provided a solution of polymer-coated metal nanoparticles obtainable by the method described above and herein.

[0017] The solution of polymer-coated metal nanoparticles may contain metal nanoparticles having an average diameter of 2-50 nm. In a preferred set of embodiments, the average diameter may be 3-12 nm, optionally 4-11 nm, 5-10, 5-9, or 6-8 nm. The median diameter may be 2-10 nm, optionally 3-9, 3-8, or 4-7 nm. The range of nanoparticle diameters within the solution may have a standard deviation of greater than 4, or in some cases greater than 4.5.

[0018] The polymer-coated metal nanoparticle solution may contain metal nanoparticles with diameters of more than 20 nm, more than 25 nm, more than 30 nm, more than 35 nm, or more than 40 nm. The polymer-coated metal nanoparticle solution may contain less than 5% nanoparticles with diameters of more than 25 nm. Optionally, the solution may contain from 0.1%, 0.25%, 0.5%, 0.75%, or 1% nanoparticles with diameters of more than 25 nm. In some embodiments, the solution may contain less than 5%, 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, 1.5%, or 1% nanoparticles with diameters of more than 25 nm.

[0019] The solution of polymer-coated metal nanoparticles can include metal nanoparticles having a polymer coating with an average thickness of 40-100 nm. Optionally, the polymer-coated metal nanoparticles can have a polymer coating with an average thickness of 50-90 nm, 55-85 nm, 60-80 nm, or 65-75 nm.

[0020] According to a third aspect of the present invention, there is provided a method of producing cellulose fibers impregnated with metal nanoparticles. The method may include (i) swelling the cellulose fibers in a second aqueous alkaline solution to form swollen cellulose fibers. The method may include (ii) removing the swollen cellulose fibers from the second aqueous alkaline solution. The method may include (iii) mixing the swollen cellulose fibers with a solution of polymer-coated metal nanoparticles to impregnate the fibers with the metal nanoparticles. The method may include (iv) separating the impregnated cellulose fibers from the solution of polymer-coated metal nanoparticles. The method may include (v) optionally washing the impregnated cellulose fibers. The method may include (vi) optionally drying the impregnated cellulose fibers. The solution of polymer-coated metal nanoparticles is obtainable by the methods described above and herein.

[0021] The method may include preparing a solution of polymer-coated metal nanoparticles according to the methods described above and herein.

[0022] In one series of embodiments, the impregnated cellulose fibers are dried in step (vi).

[0023] The method may include, prior to step (v), mixing the impregnated cellulose fibers with a solution of polymer-coated metal nanoparticles to impregnate the fibers with the polymer-coated metal nanoparticles.The method may include separating the impregnated cellulose fibers from the solution of polymer-coated metal nanoparticles.

[0024] In one set of embodiments, in step (iii), the solution of polymer-coated metal nanoparticles is maintained at a temperature of from 10 to 30° C. Optionally, the temperature may be from 15 to 25° C.

[0025] The second aqueous alkaline solution may include a Group I hydroxide, a Group I carbonate, a Group I bicarbonate, a tetraalkylammonium hydroxide, or a mixture thereof.

[0026] In one series of embodiments, step (i) comprises incubating the cellulose fibres in the second alkaline solution at a temperature between 20 and 120° C. Optionally, the temperature may be between 30, 40, 50, 60, 70, or 80° C. and 110, 100, or 95° C. In one series of embodiments, the temperature is between 80 and 100° C.

[0027] In one set of embodiments, step (ii) comprises removing the swollen cellulose fibres from the second aqueous alkaline solution and then washing them.

[0028] In one set of embodiments, the metal nanoparticles are located on both the exterior fiber surfaces and the interior fiber pore surfaces.

[0029] In one series of embodiments, the impregnated cellulose fibers have a pH of less than 7. Optionally, the impregnated cellulose fibers can have a pH of less than 6 or less than 5.

[0030] In one set of embodiments, the metal yield in the cellulose fibers is 10-25%. The metal yield is the percentage of the metal in the nanoparticle solution that is incorporated into the fibers. The metal yield can be calculated by experimentally deriving the metal content in the fibers and dividing it by the amount of metal used to form the nanoparticle solution.

[0031] According to a fourth aspect of the present invention there is provided cellulose fibres impregnated with metal nanoparticles obtainable by the method described above and herein.

[0032] The cellulose fibers may be impregnated with metal nanoparticles at a metal content of at least 1.5% w / w. The metal content may be based on the weight of the metal in the fibers and the total weight of the cellulose fibers impregnated with the metal nanoparticles. Optionally, the metal content may be at least 6% w / w.

[0033] The cellulose fibers may be configured such that the metal nanoparticles have an average diameter of 2-50 nm, preferably 10-25 nm. In one set of embodiments, the average diameter may be 3-12 nm, optionally 4-11 nm, 5-10, 5-9, or 6-8 nm. The median diameter may be 2-10 nm, optionally 3-9, 3-8, or 4-7 nm. The range of nanoparticle diameters in the solution may have a standard deviation of greater than 4, or optionally greater than 4.5.

[0034] According to a further aspect of the present invention, there is provided an absorbent material comprising a blend of cellulose fibers impregnated with the metal nanoparticles described herein and at least one other type of fiber.

[0035] In some embodiments, the at least one other type of fiber is a gelling fiber based on alginate, cellulose and modified cellulose, modified chitosan, guar gum, carrageenan, pectin, starch, polyacrylate or its copolymers, polyethylene oxide or polyacrylamide, or mixtures thereof, and / or a non-gelling fiber based on polyester, polyethylene, polyamide, cellulose, thermoplastic bicomponent fiber, glass fiber, or mixtures thereof. In one set of embodiments, the at least one other type of fiber includes carboxymethylcellulose (CMC) and lyocell.

[0036] The absorbent material may comprise 0.1-10% w / w metal (based on the total weight of the blended fibers). Optionally, the absorbent material may comprise 0.1-9, 0.2-8, 0.3-7, 0.4-6 or 0.5-5% w / w metal (based on the total weight of the blended fibers).

[0037] According to a further aspect of the present invention there is provided an absorbent article comprising the absorbent material as described above and herein. The absorbent article may be a wound care dressing.

[0038] Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0039] [Figure 1] 1 is a graph showing the silver content of fibers versus immersion time. [Diagram 2] 1 is a frequency table showing the size distribution of nanoparticles within a fiber sample. EXAMPLES

[0040] Example 1 - Silver Nanoparticles (1a-Synthesis of Silver Nanoparticles) Six separate nanoparticle solutions A through F were prepared as follows. 1. 1459 g of deionized (DI) water was placed in a first container, such as a 3 L beaker. The first container was placed in a water bath set to the temperature in Table 1. 2. 625 g of polyvinylpyrrolidone (PVP) according to Table 1 was slowly added to the beaker with mixing to form a PVP solution. 3. In a second container, 0.86 moles of sodium hydroxide and 0.20 moles of sodium carbonate were dissolved in 1096 g of DI water to form a sodium hydroxide and sodium carbonate solution. The second container was also placed in a water bath. 4. In a third container, 0.93 moles of AgNO 3 A silver nitrate solution was prepared by adding to 371 g of DI water. A third container was also placed in the water bath. 5. The first, second and third containers were all kept in the water bath until they reached the temperature of the water bath. 6. Once the first, second and third vessels had reached the temperatures shown in Table 1 below, the sodium hydroxide and sodium carbonate solution from the second vessel was added to the PVP solution in the first vessel to form an intermediate solution. 7. The silver nitrate solution was then slowly added to the intermediate solution and gently stirred. After all the silver nitrate solution was added, the reaction was continued for 20 minutes with constant gentle stirring to obtain silver nanoparticle solutions A-F. 8. The silver nanoparticles in solutions A-F have a coating that includes a polymer shell formed by PVP.

[0041] [Table 1]

[0042] (1b-Characteristics of Silver Nanoparticles) Silver nanoparticle solutions A-E, and commercial silver nanoparticles* (PVP AgPURE™, provided by RASAG) were analyzed by scanning transmission electron microscopy (STEM) using ImageJ Fiji software to determine the size of the silver core and PVP coating. The average values ​​are shown in Table 2 below.

[0043] Silver nanoparticle solutions A-E, and a commercially available silver nanoparticle* (PVP AgPURE™) were tested to determine the minimum bactericidal concentration (MBC). The MBC is the lowest concentration required to kill 99.9% of the bacteria initially plated on an agar plate and is determined by assay and serial dilution of the bactericide. Typically, a compound is considered bactericidal if the MBC is less than 4 times the minimum inhibitory concentration. The MBC was measured against Staphylococcus aureus and Pseudomonas aeruginosa and the results are shown in Table 2 below.

[0044] [Table 2]

[0045] Example 2 - Swelling of Cellulose Fibers (2a-Fiber Swelling) Swollen cellulose fibers were prepared as follows. 1. 352.8g of DI water was added to a container. 2. Then, 57.6 g of 47% NaOH solution was added to the vessel. 3. Next, 39.8g of Na 2 CO 3 was added to the vessel to form a first alkaline solution. 4. 30 g of cellulose fibers (lyocell) were added to the first alkaline solution in the container. The container containing the cellulose fibers and alkaline solution was placed in a 90° C. water bath to allow the cellulose fibers to swell. 5. The fibers were swollen in the first alkaline solution for 30 minutes. 6. After 30 minutes, the swollen fibers were removed from the first alkaline solution, squeezed to remove excess liquid, and then washed with 500 g of DI water. 7. The washed fibers were removed from the DI water and squeezed to remove excess liquid to obtain washed and swollen cellulose fibers.

[0046] (2b-modified fiber swelling) Swollen cellulose fibers were produced as follows. 1. 352.8g of DI water was added to a container. 2. Then, 57.6 g of 47% NaOH solution was added to the vessel to form a second alkaline solution. 3. 30 g of cellulose fibers (lyocell) were added to the second alkaline solution in the container to swell the fibers. 4. The fibers were allowed to swell in the second alkaline solution for 30 minutes at room temperature. 5. After 30 minutes, the swollen fibers were removed from the first alkaline solution, squeezed to remove excess liquid, and then washed with 500 g of DI water. 6. The washed fibers were removed from the DI water and squeezed to remove excess liquid to obtain washed and swollen cellulose fibers.

[0047] Example 3 - Cellulose fibers impregnated with silver nanoparticles (3a-Enhanced Fiber Treatment Process) Four examples of cellulose fibers impregnated with silver nanoparticles (Fibers 1-4) were prepared as follows. 1. 1000 ml of the silver nanoparticle solution produced according to the method in Example 1 was placed in a container according to Table 3. 2. Then, 60 g of washed, swollen, undried cellulose fibers produced according to the method of Example 2a were added to the vessel. 3. The vessel containing the silver nanoparticle solution and fiber was heated at 90° C. for 2.5 hours to form silver nanoparticle impregnated fiber. 4. After 2.5 hours, the impregnated fibers were removed from the container and squeezed to remove excess liquid. The impregnated fibers were placed in a new container. 5. In a separate container, a citric acid solution was formed by dissolving 40 g of citric acid monohydrate in 860 g of DI water. 6. The citric acid solution was added to the container containing the impregnated fiber. The citric acid solution and impregnated fiber were heated to 90°C for 30 minutes. 7. After 30 minutes, the fibers were removed from the container and squeezed to remove excess liquid. 8. The fibers were then placed in a new container and washed twice with 900g of DI water. After washing, the fibers were removed from the container and squeezed to remove excess liquid. Finally, the fibers were washed with 450g of acetone and then dried in an oven at 60°C to form fibers 1-4.

[0048] [Table 3]

[0049] (3b-Dipping Fiber Treatment Process) Three examples of cellulose fibers impregnated with silver nanoparticles (Fibers 5-7) were prepared as follows. 1. 800 ml of the silver nanoparticle solution produced according to the method in Example 1 was placed in a container according to Table 4. 2. 60 g of washed, swollen and dried cellulose fibers produced according to the method of Example 2a were then added to the vessel. 3. The fiber was placed in a container with the silver nanoparticle solution at room temperature for 2 minutes to form an impregnated fiber. 4. The impregnated fibers were removed from the container and squeezed to remove excess liquid, which was poured back into the container containing the silver nanoparticle solution. 5. The pressed fibers were dried in an oven at 90°C for 20 minutes. 6. The soaking process was repeated by placing the dried, impregnated fiber back into the container with the silver nanoparticle solution and leaving it at room temperature for an additional 2 minutes. 7. The impregnated fiber was removed from the silver nanoparticle solution and placed in a new container. 8. The impregnated fibers were then washed twice with 500 g of DI water. After washing, the fibers were removed from the container and squeezed to remove the liquid. Finally, the fibers were washed with 450 g of acetone and 4 g of Tween™ 20 (Sigma Aldrich). 9. The washed fibers were then dried in an oven at 60°C to form fibers 5-7.

[0050] [Table 4]

[0051] (3c-Soaked fiber treatment process using modified fiber swelling) Three examples of cellulose fibers impregnated with silver nanoparticles (fibers 8-10) were prepared as follows.

[0052] The process of Example 3b was repeated, except that the swollen cellulose fibers used were produced according to the method of Example 2b. The nanoparticle solutions used were those shown in Table 5 below. Fibers 8-10 were formed by this process.

[0053] [Table 5]

[0054] (3d-Soaked fiber treatment process using non-swelling fibers) Three examples of cellulose fibers impregnated with silver nanoparticles (Fibers 11-13) were prepared as follows. 1. 800 ml of the silver nanoparticle solution produced according to the method in Example 1 was placed in a container according to Table 6. 2. Then, 60 g of non-preswollen cellulose fibers (lyocell) were added to the vessel. 3. The fiber was placed in a container with the silver nanoparticle solution at room temperature for 2 minutes to form an impregnated fiber. 4. The impregnated fibers were removed from the container and squeezed to remove the liquid. The excess liquid was poured back into the container containing the silver nanoparticle solution. 5. The pressed fibers were dried in an oven at 90°C for 20 minutes. 6. The soaking process was repeated by placing the dried, impregnated fiber back into the container with the silver nanoparticle solution and leaving it at room temperature for an additional 2 minutes. 7. The impregnated fiber was removed from the silver nanoparticle solution and placed in a new container. 8. The impregnated fibers were then washed twice with 500 g of DI water. After washing, the fibers were removed from the container and squeezed to remove the liquid. Finally, the fibers were washed with 450 g of acetone and 4 g of Tween™ 20 (Sigma Aldrich). 9. The washed fibers were then dried in an oven at 60°C to form fibers 11-13.

[0055] [Table 6]

[0056] The above process is summarized in Table 7 below.

[0057] [Table 7]

[0058] Example 4 - Particle Size Measurement The size of the silver nanoparticles impregnated in fibers 1 to 13 was measured as described below, and the results are shown in Table 8. 1. A sample of Fiber 1 was mixed with epoxy resin, which was made by adding dodecenyl succinic anhydride (DDSA) and 1 drop of benzyldimethylamine (BDMA) per ml to Araldite CY212. 2. The mixture of fibers and epoxy resin was then cured in an oven at 60°C for 36–72 h to form resin-embedded fibers. 3. Samples of resin-embedded fibers were taken by sectioning the resin-embedded fibers at 85-90 nm using a Leica UC6 ultramicrotome equipped with a diamond knife. Samples were placed on 200 mesh coated copper grids. Samples were observed in an FEI Tenai TEM at an operating voltage of 80 Kv and images were recorded using Gatan Digital Micrograph software. The diameter of the silver nanoparticle cores in the PVP coating was measured using ImageJ Fiji software. 4. This process was repeated for each of fibers 2-13.

[0059] [Table 8]

[0060] Example 5 - Determination of Silver Content The silver content of fibers 1-13 was measured as follows and the results are shown in Table 9 below. 1. A sample of fiber 1 was placed in a container. 2. Nitric acid solution was added to the vessel to dissolve the silver in the fibers to form a silver solution. 3. The silver solution was titrated against potassium thiocyanate using ferric sulfate alum as an indicator. The titration was stopped when the ferric sulfate alum indicator turned reddish brown. 4. The silver content was then calculated from the amount of potassium thiocyanate used by dividing the weight of silver determined from the titration by the starting weight of fiber using the following formula:

[0061]

number

[0062] The determined silver contents are shown in Table 9 below.

[0063] [Table 9]

[0064] Example 6 - Immersion Time The effect of immersion time was investigated as follows and the results are shown in Table 10 below. 1. Swollen cellulose fibers were prepared according to the method in Example 2b above. 2. The swollen cellulose fibers were then impregnated with silver nanoparticles using nanoparticle solution A, following the method described in Example 3b. 3. The method of Example 3b was modified by changing the soaking time, which is the total time that the swollen cellulose fibers were held in the nanoparticle solution, i.e., in steps 3 and 6 of Example 3b. 4. This process was repeated varying the soak time according to Table 10. 5. The silver content of the fibers was recorded and is shown in Table 10 and Figure 1.

[0065] [Table 10]

[0066] Example 7 - Preparation of gel-forming fabric containing silver nanoparticles A gel-forming fabric containing silver nanoparticles was prepared according to the following method. 1. The fibre 5 was cut into short lengths of approximately 50mm. 2. Additional lyocell fibers that were not swollen or impregnated with silver nanoparticles were cut to the same approximate 50 mm length. 3. Samples of gel-forming carboxymethyl cellulose (CMC) fibres (SFM Limited) were also cut to lengths of approximately 50 mm. 4. The chopped fiber 5, lyocell fiber, and CMC fiber were then blended using standard nonwoven carding equipment. 14 g of fiber 5 having a silver content of 6.4% was blended with 60 g of CMC fiber and 26 g of lyocell fiber to achieve a fiber blend with 60% w / w gelled fiber and 40% w / w non-gelled fiber 5. 5. The blended fibres are then needle bonded to produce a 200gsm fibre with a silver content of 18mg / 100cm 2 A silver nanoparticle-containing gel-forming fabric was formed having the following composition:

[0067] Using the above process, a range of fabrics with different silver contents can be produced by adjusting the ratio of silver-containing fibers (i.e., fiber 5) to non-silver-containing fibers (i.e., non-impregnated lyocell fibers and CMC fibers) and / or the silver content of the silver-containing fibers. For example, in a hypothetical example using silver nanoparticle-impregnated fibers with a silver content of 3.2%, this may include 47g of silver nanoparticle-impregnated fibers, 60g of CMC fibers, and 3g of lyocell fibers. Thus, the fibers are blended in a 50:50% w / w ratio of gelled and non-gelled fibers. When carded and needle-bonded into a 120 gsm fabric, the silver content of the entire fabric is 18 mg / 100 cm. 2 become.

[0068] Fabric thickness / density is usually measured according to weight per unit area, usually grams per square meter (gsm). Fabric thickness and / or density of silver nanoparticle-containing gel-forming fabrics can be adjusted by adjusting the operating parameters of the textile equipment in a manner known to those skilled in the art. For example, the weight of the fiber fed to the card, the speed of the take-up belt and the cross folder can all be varied to change the desired output. In two examples, silver nanoparticle-containing gel-forming fabrics were prepared at 120 gsm (Fabric 14) and 200 gsm (Fabric 15).

[0069] Example 8 - Release of Silver from Nonwoven Fabric The amount of silver released by fabrics produced by the process described in Example 7 was investigated and compared to commercially available silver-containing fabrics, and the results are shown in Table 11 below. 1. 50ml of distilled water was added to a 100ml flask. 2. 25cm of fabric 14 2 The samples were added to flasks containing distilled water, the flasks were capped to prevent evaporation, and incubated at 37°C with agitation at 40 rpm. 3. After 5 minutes, 1.0 ml of liquid was removed from the flask. 1.0 ml of fresh distilled water was added to the flask. 4. 1 ml of the liquid removed from the flask was tested to determine the silver concentration in the liquid by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). 5. Steps 3 and 4 were repeated after 10 minutes, 30 minutes, 1 hour and 5 hours and the silver concentrations were recorded in Table 11. 6. Steps 1-5 above were repeated for Fabric 15 and Comparative Fabrics 16 and 17.

[0070] [Table 11]

[0071] Aquacel™ Ag Extra is a carboxymethylcellulose fabric containing ionic silver supplied by Convatec™ (Reading, UK). Kerracel™ Ag is a carboxymethylcellulose dressing containing an argentate supplied by 3M (St. Paul, Minnesota, USA).

[0072] Example 9 - Determination of antibacterial efficacy of fabrics The antimicrobial properties of gel-forming fabrics containing silver nanoparticles were investigated as follows. 1. Six gel-forming fabrics containing silver nanoparticles were prepared according to the method of Example 7, except that fiber 8 was used instead of fiber 5. 2. Six fabrics were produced with different fabric weights as shown below in Table 12. The silver content of the fabrics was achieved by varying the relative proportion of fiber 8 compared to the lyocell and CMC fibers to form fabrics 18-23. 3. The antimicrobial properties of each of Fabrics 18-23 were evaluated using the following modified AATCC-100 test method. 17.6cm of each fabric 18~23 2 The test samples were sterilized using gamma irradiation. Each of the sterilized test samples was then saturated with simulated wound fluid as known to those skilled in the art. Each saturated test sample was incubated at 37° C. for 4 days and then diluted with 1×0 -6cfu (colony forming units) of bacteria were inoculated. The inoculated fabrics were then incubated undisturbed in a sealed jar for 24 hours. After 24 hours, viable bacteria were harvested, counted, and the log reduction was calculated.

[0073] [Table 12]

[0074] Example 10 Relationship between molecular weight of nanoparticles and minimum bactericidal concentration The minimum bactericidal concentration of the nanoparticle solution was investigated as follows. 1. Four silver nanoparticle solutions were prepared according to Table 13 below. The method was the same as that described in Example 1, except that the PVP used was selected from Table 13 and the water bath temperature was set to 90°C, producing nanoparticle solutions A and G-I.

[0075] [Table 13]

[0076] The minimum bactericidal concentrations (MBC) of silver nanoparticle solutions A and G to I were determined and are shown in Table 14 below.

[0077] [Table 14]

[0078] Nanoparticle solutions A (10,200 ppm) and G (11,960 ppm) produced the highest concentration of silver nanoparticles in solution. Analysis of the nanoparticle solutions was performed using an Analytic Jena Speccord 205 spectrophotometer. The UV-VIS analysis consisted of obtaining the lambda maximum (wavelength corresponding to the highest absorbance), the aggregation ratio (the intensity of the absorbance at the lambda maximum divided by the intensity of the absorbance at approximately 500 nm), and the concentration of nanoparticles. Nanoparticle solution G produced the largest concentration of silver nanoparticles, lambda. max Nanoparticle solution A had an aggregation ratio (λ at 400-410 nm). maxNanoparticle solution I had the lowest amount of aggregated silver nanoparticles as evidenced by the ratio of absorbance at 500 nm to absorbance at 500 nm. Nanoparticle solution I had the lowest minimum bactericidal concentration (0.15 ppm for S. aureus and 0.58 ppm for E. coli). Without wishing to be overly bound to a particular theory, it is desirable to have a high nanoparticle concentration to maximize the efficiency of the process and avoid wasting silver. A low minimum bactericidal concentration is desirable to maximize the antibacterial effect of the nanoparticles. A high aggregation ratio (low amount of aggregated particles compared to individual particles) is desirable because it is understood that aggregated particles have a smaller surface area per unit mass than smaller individual nanoparticles, which improves antibacterial performance.

[0079] Example 11 - Odor Control The odor control capabilities of gel-forming fabrics containing silver nanoparticles were investigated as follows.

[0080] A gel-forming fabric containing silver nanoparticles (Fabric 24) was prepared according to the method of Example 7, except that Fiber 8 was used instead of Fiber 5. Fabric 24 was then compared to four commercially available bandages shown in Table 15.

[0081] Testing was carried out by the Surgical Materials Testing Laboratory (Cardiff, UK) in accordance with SMTL test method TM-283. The method used is as follows: 1. A test sample of fabric according to Table 15 was placed on a well in a stainless steel plate and covered with a Perspex™ dome. A 50 ml syringe attached to a syringe driver was filled with 2% diethylamine solution. 2. A 2% diethylamine solution was then injected through the well onto the test sample via a syringe driver set at an injection rate of 30 ml / hour. 3. The time it took for the gas analyzer to detect a diethylamine concentration of 15 ppm was recorded. 4. The amount of test solution applied to the dressing was calculated. 5. The test was performed in triplicate.

[0082] [Table 15]

[0083] Example 12 - Drying The importance of the drying step in the production of silver nanoparticle-containing fibers was investigated as follows. 1. Two samples of fiber 8 were prepared as follows. 2. A first 250 g sample of fiber 8 was prepared according to Example 3c above and scaled up accordingly. All drying steps during the soaking process were carried out in an oven that held the other eight batches of fiber being dried. Thus, the atmosphere in the oven had a high relative humidity (e.g., 25% or more) to form fiber 8a. 3. A second 250 g sample of fiber 8 was prepared according to Example 3c above and scaled up accordingly, with all drying steps during the soaking process carried out in an oven and moisture immediately removed from the oven using an extraction fan to form fiber 8b. 4. Two gel-forming fabrics containing silver nanoparticles were produced according to Example 7, except that the first fabric used fiber 8a and the second fabric used fiber 8b. 5. The antibacterial efficacy of the two fabrics was measured according to the method of Example 9, and the results were recorded in Table 16.

[0084] [Table 16]

[0085] Example 13 - Comparison with WO 2015 / 040435 1. A first sample of fiber 8 was prepared according to the method of Example 3c. 2. A second sample of fiber was prepared according to the method of Example 1.1a described in WO 2015 / 040435 (Comparative Fiber 29). Comparative Fiber 29 is a cellulose fiber impregnated with silver nanoparticles. 3. The silver content of fiber 8 and comparative fiber 29 was measured according to the method described in Example 5. 4. The silver yield was then calculated based on the mass balance. The silver yield is the yield of silver present in the fiber divided by the total mass of silver present in the silver nitrate used to form the fiber, expressed as a percentage. A silver yield of 100% indicates that all of the silver in the silver nitrate was incorporated into the fiber as silver nanoparticles. The silver yield was calculated over multiple replicate samples of fiber 8 producing the ranges shown in Table 17.

[0086] [Table 17]

[0087] Three further samples of fiber 8 (fiber 8a-c) and comparative fiber 29 were tested to investigate the size distribution of silver nanoparticles within the fiber samples. Tests were performed using STEM and ImageJ Fiji software to measure the nanoparticles observed, and the total number of particles of each size was counted and plotted in a frequency table in Figure 2. Values ​​are presented as a percentage of the total number of nanoparticles counted. The average of the data was calculated, as shown below in Table 18.

[0088] [Table 18]

[0089] Without wishing to be bound by any particular theory, it is understood that the nanoparticles in fibers 8a-c were less uniform than those in comparative fiber 29, which was densely packed at 2-10 nm and had the largest nanoparticle observed at 23 nm. In contrast, the average nanoparticle diameter was observed to be larger in fibers 8a-c, with the majority of the nanoparticles in the range of 3 nm to 12 nm, with a small number of particles up to 50 nm in diameter. The standard deviation for fibers 8a-c was larger than that for comparative fiber 29, indicating a wider spread in nanoparticle sizes. It is believed that the reduced uniformity and the presence of larger nanoparticles contribute to the longer lasting effect of fiber 8 compared to existing fibers.

[0090] Example 14 - Cytotoxicity A sample of fabric 24 was prepared according to the method of Example 10 using fiber 8 with a gelled to non-gelled fiber ratio of 60:40. The proportion of silver-containing fiber in the non-gelled fiber portion was adjusted to a silver content of 18 mg / 100 cm. 2 The cytotoxicity of fabric 24 was tested by NAMSA according to the method of ISO 10993-5.

[0091] The test was repeated against existing silver-containing fabrics. Comparative fabric 29 is a calcium alginate material containing ionic silver produced by the applicant.

[0092] [Table 19]

[0093] Fabric 24 showed higher cell viability and lower in vitro cytotoxicity than the control fabrics.

Claims

1. A method for producing a solution of polymer-coated metal nanoparticles, comprising: (a) mixing a first aqueous alkali solution with an aqueous polymer solution to form an alkaline polymer aqueous solution; (b) mixing the alkaline polymer aqueous solution with an aqueous solution of a metal salt to form a solution of polymer-coated metal nanoparticles. A method for producing a solution of polymer-coated metal nanoparticles, comprising the steps of (a) and (b).

2. The method according to claim 1, wherein the first aqueous alkali solution contains a Group I hydroxide, a Group I carbonate, a Group I bicarbonate, a tetraalkylammonium hydroxide, or a mixture thereof; preferably, the first aqueous solution contains sodium hydroxide and sodium carbonate.

3. The method according to claim 1, wherein the metal salt contains a metal selected from the group consisting of silver, copper, zinc, selenium, gold, cobalt, nickel, zirconium, molybdenum, gallium, iron, or any combination thereof; preferably, the metal is silver, and / or the metal salt is a nitrate, acetate, carbonate, bicarbonate, sulfate, or a mixture thereof; preferably, the metal salt is a nitrate.

4. The method according to claim 1, wherein the polymer is selected from the group consisting of polyamide, polyimide, polyethyleneimine, polyvinyl alcohol, pectin, albumin, gelatin, carrageenan, gum, cellulose or its derivatives, poly(N-vinylpyrrolidone), poly(N-vinylcaprolactam), and mixtures thereof; preferably, the polymer is poly(N-vinylpyrrolidone), and / or the polymer has a weight average molecular weight (Mw) of 20 to 80 kg / mol, optionally, the polymer is poly(N-vinylpyrrolidone) and the polymer has a weight average molecular weight (Mw) of 30 to 40 kg / mol.

5. The method according to claim 1, wherein the solution of polymer-coated metal nanoparticles can be obtained in the absence of any additional reducing agent.

6. The method according to claim 1, wherein in step (b), the mixing is carried out at a temperature of 20 to 120°C, preferably 60 to 100°C.

7. A solution of polymer-coated metal nanoparticles obtainable by the method according to claim 1, Optionally, the average diameter of the metal nanoparticles is 2 to 50 nm, preferably 3 to 12 nm, Optionally, the metal nanoparticles are a solution of polymer-coated metal nanoparticles having a polymer coating with an average thickness of 40 to 100 nm.

8. A method for producing cellulose fibers impregnated with metal nanoparticles, (i) swelling cellulose fibers in a second aqueous alkali solution to form swollen cellulose fibers; (ii) removing the swollen cellulose fibers from the second aqueous alkali solution; (iii) mixing the swollen cellulose fibers with a solution of polymer-coated metal nanoparticles to impregnate the fibers with the metal nanoparticles; (iv) separating the impregnated cellulose fibers from the solution of polymer-coated metal nanoparticles; (v) optionally, washing the impregnated cellulose fibers; (vi) optionally, washing the impregnated cellulose fibers; comprising The method for producing cellulose fibers impregnated with metal nanoparticles, wherein the solution of polymer-coated metal nanoparticles can be obtained by the method according to claim 1 or is as described in claim 7.

9. The method according to claim 8, comprising the step of preparing the solution of polymer-coated metal nanoparticles according to the method according to claim 1.

10. In step (vi), the impregnated cellulose fibers are dried, Optionally, before step (v), the impregnated cellulose fibers are mixed with a solution of polymer-coated metal nanoparticles to impregnate the fibers with the polymer-coated metal nanoparticles, and the impregnated cellulose fibers are separated from the solution of polymer-coated metal nanoparticles. The method according to claim 8, comprising the steps of:

11. In step (iii), the solution of polymer-coated metal nanoparticles is maintained at a temperature of 10 to 30 °C, preferably 15 to 25 °C, and / or The second aqueous alkali solution contains a Group I hydroxide, a Group I carbonate, a Group I bicarbonate, a tetraalkylammonium hydroxide, or a mixture thereof, and / or Step (i) includes incubating the cellulose fiber in the second alkaline solution at a temperature of 20 to 120 °C, preferably 60 to 100 °C, and / or Step (ii) includes washing the swollen cellulose fiber after removing it from the second aqueous alkaline solution, and / or The method according to claim 8, wherein the metal nanoparticles are located on both the outer fiber surface and the inner fiber pore surface.

12. The impregnated cellulose fiber has a pH of less than 7, and / or The method according to claim 8, wherein the metal yield in the cellulose fiber is 10 to 25%.

13. A cellulose fiber impregnated with metal nanoparticles, which can be obtained by the method according to claim 8, Optionally, the cellulose fiber impregnated with the metal nanoparticles is impregnated with metal nanoparticles at a metal content of at least 1.5% w / w (based on the weight of the metal and the total weight of the cellulose fiber impregnated with the metal nanoparticles), preferably at least 6% w / w (based on the weight of the metal and the total weight of the cellulose fiber impregnated with the metal nanoparticles), Optionally, the cellulose fiber impregnated with the metal nanoparticles has an average diameter of the metal nanoparticles of 2 to 50 nm, preferably 10 to 25 nm.

14. An absorbent material comprising a blend of the cellulose fiber impregnated with the metal nanoparticles according to claim 13 and at least one other type of fiber, Optionally, the at least one other type of fiber is Gel-forming fibers based on alginate, cellulose and modified cellulose, modified chitosan, guar gum, carrageenan, pectin, starch, polyacrylate or its copolymer, polyethylene oxide or polyacrylamide, or mixtures thereof, and / or Non-gel-forming fibers based on polyester, polyethylene, polyamide, cellulose, thermoplastic composite fiber, glass fiber, or mixtures thereof wherein Optionally, the at least one other type of fiber includes carboxymethyl cellulose (CMC) and lyocell, and / or The absorbent material contains 0.1 to 10% w / w of metal (based on the total weight of the blend fibers), preferably 0.5 to 5% w / w of metal (based on the total weight of the blend fibers).

15. An absorbent article comprising the absorbent material according to claim 14, Optionally, the absorbent article is an absorbent article which is a bandage for wound treatment.

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