Preparation method and application of nano antibacterial cashmere fiber

Abstract

The invention relates to the technical field of textile functional finishing, and discloses a preparation method and application of nano-antibacterial cashmere fibers.The preparation method adopts a step-by-step synergistic strategy, and cashmere fibers are sequentially subjected to activation complexing, bionic in-situ mineralization and enzymatic crosslinking self-locking treatment; firstly, a system containing zinc salt and polypeptide is used for achieving anchoring and catalysis of functional elements on the fiber surface; then, in-situ generation of a nano-antibacterial precursor is induced under a mild condition; and finally, constructing a cross-linked network among fiber keratin molecules by using transglutaminase, and carrying out physical fixation and self-locking on the generated antibacterial functional components. By means of the method, on the premise that the original breaking strength and soft hand feeling of cashmere fibers are not damaged, the cashmere fibers are endowed with excellent and durable antibacterial performance, and after 50 times of standard washing, the antibacterial rate can still be kept very good; in addition, the fiber prepared by the method has no cytotoxicity and has good biocompatibility.

Description

Technical Field

[0001] This invention relates to the field of textile functional finishing technology, specifically to a method for preparing nano-antibacterial cashmere fiber and its application. Background Technology

[0002] Cashmere fiber, as a precious natural protein fiber, is highly favored for its excellent softness, warmth, and skin-friendliness. However, cashmere is rich in keratin, which makes it a breeding ground for microorganisms in humid and warm environments. This can not only lead to problems such as odor and discoloration, but also pose a potential threat to human health. Therefore, applying antibacterial finishing to cashmere products is an important technical means to enhance their added value and performance.

[0003] Currently, the antibacterial finishing of protein fibers such as cashmere typically employs a technical approach of loading organic antibacterial agents or inorganic antibacterial nanoparticles onto the fiber surface through impregnation, coating, or other methods. However, this approach generally suffers from an inherent technical contradiction: on the one hand, the binding between antibacterial functional components and fibers largely relies on physical adsorption or weak van der Waals forces. This binding method is not strong, leading to a significant loss of antibacterial agents during repeated washing and wear friction, resulting in a sharp decline in antibacterial performance and making it difficult to achieve a long-lasting and effective antibacterial effect.

[0004] On the other hand, in an attempt to improve the binding strength of functional components, some existing processes use relatively harsh treatment conditions such as resin crosslinking agents or high-temperature baking; however, the keratin structure and surface scale layer of cashmere fibers are extremely delicate and sensitive, and the above treatment conditions will cause irreversible damage to them; this damage is specifically manifested in the decrease of the original breaking strength of the fiber and the loss of the characteristic soft hand feel, that is, the fiber becomes brittle and hard, which seriously undermines the core value of cashmere as a high-end textile raw material.

[0005] Therefore, this invention proposes a method for preparing nano-antibacterial cashmere fibers and their applications to address the shortcomings of existing technologies. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for preparing nano-antibacterial cashmere fibers and their applications, solving the problems of not being able to impart durable and washable antibacterial properties to protein fibers such as cashmere without damaging their physical properties and feel, and the difficulty in achieving synergistic integration of multiple functions.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] The first aspect of this invention provides a method for preparing nano-antibacterial cashmere fibers, the method comprising the following steps:

[0009] S1. Immerse cashmere fibers in an activated complexing catalytic solution and treat them under preset acidic pH and temperature conditions. In this step, the antibacterial metal salt, bioactive peptide inducer, and synergistic functional molecule precursor in the activated complexing catalytic solution work together on the cashmere fibers. Specifically, the metal ions in the antibacterial metal salt penetrate into the keratin structure of the cashmere fibers and coordinate with the functional groups on the keratin molecular chain. At the same time, the metal ions act as a catalyst, catalyzing the hydrolysis reaction of the synergistic functional molecule precursor in the same solution, generating synergistic functional molecules in situ.

[0010] S2. Without changing the treatment bath, add a biomimetic in-situ mineralization solution to the bath in step S1 to adjust the pH value of the bath from acidic to a preset alkaline range; the change in pH value causes the metal ions that have been complexed with the keratin molecular chain in step S1 to undergo an in-situ precipitation reaction, and nano antibacterial particles are generated using the keratin molecular chain as a template.

[0011] S3. The cashmere fibers treated and cleaned in step S2 are immersed in an enzymatic cross-linking self-locking solution containing transglutaminase and treated under preset neutral pH and temperature conditions. In this step, transglutaminase catalyzes the formation of new covalent bonds between the keratin molecular chains of the cashmere fibers, forming a three-dimensional cross-linked network structure. This network structure physically fixes the antibacterial nanoparticles generated in step S2 and the synergistic functional molecules generated in situ in step S1 into the internal structure of the cashmere fibers.

[0012] In one specific implementation, the processing conditions for step S1 are: pH value of 5.5 to 6.5, temperature of 35 to 45°C, and processing time of 40 to 60 minutes.

[0013] In one specific embodiment, the activated complexing catalyst comprises the following components in parts by weight: 1.0 to 4.0 parts of antibacterial metal salt, 0.1 to 0.5 parts of bioactive polypeptide inducer, 0.1 to 0.4 parts of synergistic functional molecule precursor, 0.5 to 2.0 parts of sodium citrate buffer, and 100 to 200 parts of deionized water.

[0014] In a more specific embodiment, the synergistic functional molecular precursor is (2,2-dimethyl-1,3-dioxolane-4-yl)methyl ester-5-(1,2-dithiopentane-3-yl)valerate, which is prepared by the following steps:

[0015] α-Lipoic acid is esterified with a polyol under the action of a catalyst to generate a polyol ester of α-lipoic acid.

[0016] The hydroxyl groups in the obtained polyol ester that did not participate in the esterification reaction were protected to obtain the (2,2-dimethyl-1,3-dioxolane-4-yl)methyl ester-5-(1,2-dithiopentane-3-yl)valerate.

[0017] The antibacterial metal salt is zinc acetate, and the biopeptide inducer is arginine-glycine-aspartic acid tripeptide.

[0018] In one specific embodiment, the processing conditions for step S2 are as follows: the pH value of the bath solution is adjusted to 8.5-9.5, and the processing time is 20-40 minutes; the biomimetic in-situ mineralization solution is prepared by dissolving sodium bicarbonate and glycerol in deionized water, wherein the amount of glycerol added is 1.0%-3.0% of the dry weight of cashmere fibers.

[0019] In one specific embodiment, the processing conditions for step S3 are: pH value of 6.0-7.0, temperature of 40-50℃, and processing time of 30-60 minutes; the enzyme activity concentration of transglutaminase in the enzymatic cross-linking self-locking solution is 10-30 U / mL.

[0020] In a preferred embodiment, the preparation method further includes step S4: drying the cashmere fibers treated in step S3 at a temperature of 75-85°C, wherein the drying process simultaneously inactivates the transglutaminase.

[0021] A second aspect of the present invention provides a nano-antibacterial cashmere fiber prepared by any of the foregoing methods.

[0022] A third aspect of the present invention provides the application of the aforementioned nano-antibacterial cashmere fiber in the preparation of infant and toddler underwear, high-end functional clothing or medical and health textiles.

[0023] This invention provides a method for preparing nano-antibacterial cashmere fibers and their applications. It has the following beneficial effects:

[0024] 1. The preparation method of the present invention generates nano-antibacterial particles in situ inside the fiber and uses transglutaminase to catalyze the formation of a three-dimensional cross-linked network of keratin molecular chains, thereby physically locking the nano-antibacterial particles and synergistic functional molecules in the network. This method of fixing the functional components from inside the fiber makes the functional components less likely to fall off during subsequent washing and friction, thus endowing cashmere fibers with durable and wash-resistant antibacterial properties.

[0025] 2. The preparation method of the present invention is carried out under mild process conditions throughout, including a near-neutral pH range and a low processing temperature. These process conditions avoid the damage to the cashmere keratin structure caused by strong acids, strong alkalis or high-temperature baking, and can effectively maintain the integrity of the original secondary and tertiary structures of cashmere fibers. Thus, while giving it new functions, it retains the unique softness, elasticity and physical strength of cashmere fibers to the greatest extent.

[0026] 3. The technical solution of this invention embodies the integrated design of process steps and component functions; wherein complexation and mineralization are completed by adjusting the pH value in the same bath, which simplifies the process flow and reduces wastewater discharge; at the same time, the antibacterial metal salt has the dual functions of a nanoparticle precursor and a synergistic functional molecular precursor hydrolysis catalyst; thus, multiple functions can be synergistically endowed in a simplified and continuous process flow, thereby improving production efficiency. Attached Figure Description

[0027] Figure 1 This is a flowchart of the preparation process of the present invention;

[0028] Figure 2 This is a comparison chart of the antibacterial rates of the embodiments and comparative samples of the present invention before and after washing;

[0029] Figure 3 This is a comparison chart of the fracture strength test results of the embodiments and comparative samples of the present invention;

[0030] Figure 4 This is a comparison chart of the bending length test results of the embodiments and comparative samples of the present invention;

[0031] Figure 5 This is a comparison chart of the adhesion rates of functional components in Example 1 and Comparative Example 2 of the present invention. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0034] Cashmere fiber: 26 / 2 worsted cashmere yarn, with an average fiber fineness of 14.5-15.5μm and a length of 34-36mm;

[0035] α-Lipoic acid (CAS: 62-46-4): Purity ≥99%;

[0036] Glycerol (CAS: 56-81-5): Analytical grade;

[0037] Dichloromethane (CAS: 75-09-2): Analytical grade;

[0038] p-Toluenesulfonic acid monohydrate (CAS: 6192-52-5): Purity ≥ 98.5%;

[0039] Sodium bicarbonate (CAS: 144-55-8): Analytical grade;

[0040] Anhydrous magnesium sulfate (CAS: 7487-88-9): Analytical grade;

[0041] Ethyl acetate (CAS: 141-78-6): analytical grade;

[0042] n-Hexane (CAS: 110-54-3): Analytical grade;

[0043] 2,2-Dimethoxypropane (CAS: 77-76-9): Purity ≥98%;

[0044] Triethylamine (CAS: 121-44-8): Analytical grade;

[0045] Citric acid (CAS: 77-92-9): analytical grade;

[0046] Trisodium citrate dihydrate (CAS: 6132-04-3): Analytical grade;

[0047] Zinc acetate dihydrate (CAS: 5970-45-6): analytical grade;

[0048] Arginine-glycine-aspartic acid tripeptide (CAS: 99896-85-2): Purity ≥98%;

[0049] Sodium dihydrogen phosphate (CAS: 7558-80-7): Analytical grade;

[0050] Disodium hydrogen phosphate (CAS: 7558-79-4): Analytical grade;

[0051] Transglutaminase (CAS: 80146-85-6): Food grade, enzyme activity ≥100U / g.

[0052] Preparation Example 1: Preparation of Synergistic Functional Molecular Precursors

[0053] This embodiment provides a specific method for preparing a synergistic functional molecular precursor named (2,2-dimethyl-1,3-dioxolane-4-yl)methyl ester-5-(1,2-dithiopentane-3-yl)valerate; the method includes the following steps:

[0054] (1) Intermediate synthesis: Preparation of glycerol-α-lipoic acid ester

[0055] In a reaction vessel, 1.0 equivalent of α-lipoic acid and 3.0–4.0 equivalents of glycerol were added, with dichloromethane as the solvent. The reaction vessel was cooled in an ice bath, and then 0.05–0.10 equivalents of p-toluenesulfonic acid monohydrate were slowly added as a catalyst. The reaction system was continuously stirred magnetically for 24–36 hours under a nitrogen atmosphere and at a temperature of 20–25°C. After the reaction, the obtained organic phase was washed successively with saturated sodium bicarbonate aqueous solution, deionized water, and saturated brine. The separated organic phase was dried over anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: a gradient mixture of ethyl acetate and n-hexane) to obtain the target intermediate product, glycerol-α-lipoic acid ester.

[0056] (2) Synthesis of target product: diol protection reaction of intermediate

[0057] The purified intermediate (1.0 equivalent) obtained in step (1) was dissolved in anhydrous dichloromethane, followed by the addition of 1.5 to 2.0 equivalents of 2,2-dimethoxypropane and 0.01 to 0.02 equivalents of p-toluenesulfonic acid monohydrate. The reaction system was stirred at 20 to 25 °C for 6 to 10 hours, and the reaction progress was monitored by thin-layer chromatography (TLC). After the reaction was complete, triethylamine was added to quench the reaction. The solvent and excess 2,2-dimethoxypropane were removed by rotary evaporation. The residue was purified again by silica gel column chromatography (eluent: a gradient mixture of ethyl acetate and n-hexane) to obtain the final target product, namely (2,2-dimethyl-1,3-dioxolane-4-yl)methyl ester-5-(1,2-dithiopentane-3-yl)valerate.

[0058] Examples 1-3:

[0059] See attached document Figure 1 To further illustrate the present invention, the preparation method of the nano-antibacterial cashmere fiber provided by the present invention will be described in detail below with reference to the embodiments.

[0060] Example 1: This example provides a method for preparing nano-antibacterial cashmere fibers, specifically including the following steps:

[0061] (1) Preparation of functional solutions

[0062] Preparation of Solution A (Activated Complexing Catalyst): Citric acid and trisodium citrate dihydrate were dissolved in deionized water to prepare a buffer solution with a concentration of 0.1 mol / L, and its pH was adjusted to 6.0. Subsequently, zinc acetate dihydrate, arginine-glycine-aspartic acid tripeptide and the co-functional molecular precursor prepared in Example 1 were dissolved in the buffer solution in sequence, and stirred until all components were completely dissolved. The final concentrations of each component were as follows: zinc acetate dihydrate 0.5 wt%, arginine-glycine-aspartic acid tripeptide 0.1 wt%, and co-functional molecular precursor 0.05 wt%.

[0063] Preparation of Solution B (Bionic In-situ Mineralization Solution): Dissolve glycerol in deionized water to a final concentration of 1.5 wt%; then add sodium bicarbonate powder to the solution until the pH value of the solution stabilizes at 9.0.

[0064] Preparation of Solution C (enzyme-linked self-locking solution): Dissolve sodium dihydrogen phosphate and disodium hydrogen phosphate in deionized water to prepare a phosphate buffer (PBS) with a concentration of 0.05 mol / L, and adjust its pH to 6.5; before use, disperse transglutaminase powder in the buffer to achieve an enzyme activity concentration of 20 U / mL.

[0065] (2) Processing technology of cashmere fibers

[0066] The impregnation process is adopted, and the liquor ratio (the ratio of fiber dry weight to working liquid volume) is controlled at 1:30.

[0067] Step 1 (Pretreatment): Soak cashmere fibers in deionized water at 40℃ for 20 minutes. Centrifuge to control the liquid content of the fibers to 80%.

[0068] Step 2 (Activation, Complexation and In-situ Catalysis): Immerse the pretreated cashmere fibers in the prepared solution A and turn them over at 15 rpm for 50 minutes at a constant temperature of 40°C.

[0069] Step 3 (Intermediate Wash): Remove the fibers and rinse them twice in deionized water at 25°C, with each rinse lasting 10 minutes.

[0070] Step 4 (Bionic In-situ Mineralization): Immerse the intermediate-washed fibers in the prepared solution B and treat them at a constant temperature of 28°C for 30 minutes.

[0071] Step 5 (Second cleaning): Remove the fibers and rinse them in deionized water until the pH of the washing effluent is neutral.

[0072] Step 6 (Enzymatic cross-linking and self-locking): Immerse the fibers that have undergone two cleanings in freshly prepared solution C and treat them at a constant temperature of 45°C for 45 minutes.

[0073] Step 7 (Post-processing and finishing): Heat the fibers treated in Step 6 together with solution C to 80°C and hold for 15 minutes;

[0074] Then, rinse it clean with deionized water;

[0075] Finally, it is dried at a temperature of 60°C.

[0076] Example 2: The preparation method in this example is basically the same as that in Example 1, except that:

[0077] In step (1), during the preparation of the functional solution:

[0078] The final concentration of zinc acetate dihydrate in solution A is 0.1 wt%.

[0079] The enzyme activity concentration of transglutaminase in solution C is 10 U / mL.

[0080] In step (2), the cashmere fiber processing technology:

[0081] The processing time for step two is 40 minutes;

[0082] The processing time for step six is ​​30 minutes.

[0083] The remaining steps and parameters are the same as in Example 1.

[0084] Example 3: The preparation method in this example is basically the same as that in Example 1, except that:

[0085] In step (1), during the preparation of the functional solution:

[0086] The final concentration of zinc acetate dihydrate in solution A is 1.0 wt%;

[0087] The enzyme activity concentration of transglutaminase in solution C is 30 U / mL.

[0088] In step (2), the cashmere fiber processing technology:

[0089] The processing time for step two is 60 minutes;

[0090] The processing time for step six is ​​60 minutes.

[0091] The remaining steps and parameters are the same as in Example 1.

[0092] Comparative Examples 1-4:

[0093] Comparative Example 1:

[0094] Untreated raw cashmere fibers were used as blank control samples.

[0095] Comparative Example 2:

[0096] Compared with Example 1, the difference is that in the preparation of the functional solution in step (1), solution C is only a phosphate buffer with a pH of 6.5 and does not contain transglutaminase. The remaining steps and parameters are the same as in Example 1.

[0097] Comparative Example 3:

[0098] The difference from Example 1 is that, in step (1) of preparing the functional solution, the synergistic functional molecule precursor obtained in Preparation Example 1 is not added during the preparation of solution A. The remaining steps and parameters are the same as in Example 1.

[0099] Comparative Example 4:

[0100] The difference compared to Example 1 is that a one-step processing method was used. All functional components (zinc acetate dihydrate, arginine-glycine-aspartic acid tripeptide, co-functional precursor, and transglutaminase) from solutions A and C in Example 1 were added all at once in a single bath to a buffer solution with a pH of 7.0, and treated at 45°C for 60 minutes. The remaining pretreatment and post-treatment...

[0101] Test Examples 1-4:

[0102] Test Example 1: Antibacterial and Washability Test

[0103] To verify the antibacterial properties and durability of the cashmere fibers prepared in the embodiments of the present invention, antibacterial properties tests were conducted on the samples obtained in Examples 1-3 and Comparative Examples 1-4.

[0104] The testing method is as follows:

[0105] Antimicrobial performance evaluation: conducted according to GB / T-20944.3-2008 "Textiles - Evaluation of antimicrobial properties - Part 3: Shaking method"; the test strains were Staphylococcus aureus (ATCC-6538) and Candida albicans (ATCC-10231); to simplify the data presentation, the average value of the inhibition rate of the two strains was taken as the final inhibition rate result in this example.

[0106] Washability evaluation: The samples were washed 50 times according to the procedure specified in GB / T8629-2017 "Textiles - Test procedures for household washing and drying". After washing, the samples were air-dried at room temperature and then antibacterial performance was tested.

[0107] The experimental steps are as follows:

[0108] Sample preparation: Samples were taken from the dried cashmere fiber samples obtained in Examples 1-3 and Comparative Examples 1-4. Each sample was divided into two groups: one group was used for pre-wash testing, and the other group was used for post-wash testing.

[0109] Washing treatment: The sample group to be tested after washing was subjected to 50 washing and drying cycles according to the above GB / T-8629-2017 standard.

[0110] Antibacterial test: All samples before and after washing, together with the blank sample of Comparative Example 1, were tested using the shaking method according to GB / T-20944.3-2008 standard. After inoculating the quantitative samples with quantitative bacterial suspension, they were incubated in a constant temperature shaking incubator under specific conditions for 18 hours.

[0111] Results Calculation: After incubation, the number of surviving colonies on each sample was calculated using the plate count method, and the inhibition rate was calculated according to the standard formula:

[0112] ;

[0113] In the formula, Indicates the antibacterial rate, expressed as a percentage (%). The value represents the average viable bacterial concentration of the blank control sample (i.e., Comparative Example 1 in this test case, cashmere fibers without any antimicrobial treatment) after 18 hours of shaking incubation, expressed in CFU / mL (colony forming units per milliliter). This value represents the natural growth level of the strain on the sample under conditions without antimicrobial intervention. The value represents the average viable bacterial concentration of the antimicrobial test sample (i.e., Examples 1-3 or Comparative Examples 2-4 in this test example) after shaking culture for 18 hours under the same conditions as the blank control sample, and the unit is also CFU / mL; this value represents the level of bacterial strains still surviving on the sample after antimicrobial treatment.

[0114] The experimental results are shown in Table 1:

[0115] The antibacterial performance test results of each sample are recorded in Table 1.

[0116] Table 1: Antibacterial performance test results of each example and comparative sample

[0117] sample Antibacterial rate before washing (%) Antibacterial rate (%) after 50 washes Example 1 99.2 96.5 Example 2 99.1 93.8 Example 3 99.4 97.1 Comparative Example 1 5.3 4.8 Comparative Example 2 99.0 45.7 Comparative Example 3 95.5 90.2 Comparative Example 4 68.4 25.1

[0118] Results Analysis: The data in Table 1 show that the samples prepared in Examples 1-3 all exhibited antibacterial rates exceeding 93% after both unwashed and 50 washes. (See attached table.) Figure 2As shown; in contrast, the untreated sample of Comparative Example 1 had virtually no antibacterial ability; this result indicates that the activation complexation and in-situ mineralization steps in this technical solution successfully generated antibacterial components on the fiber and endowed the cashmere fiber with initial antibacterial properties.

[0119] Further comparison of the results of each sample after 50 washes is shown in the attached figure. Figure 2 As shown, the antibacterial rate of the samples in Examples 1-3 remained above 93%; the antibacterial rate of the sample in Comparative Example 2, due to the lack of transglutaminase, decreased significantly from 99.0% to 45.7% after washing. This data proves that the enzymatic cross-linking self-locking step forms a cross-linking network structure between the fibrous keratin molecular chains. This structure physically fixes the in-situ generated antibacterial components inside the fiber, thereby effectively preventing their shedding during repeated washing and achieving a durable antibacterial effect.

[0120] Comparative Example 4, which uses a one-step mixing process, showed significantly lower antibacterial rates (68.4% and 25.1%) before and after washing compared to Example 1. This result indicates that the stepwise processing method used in this technical solution is necessary. This stepwise process ensures that the reactions at each stage are carried out under optimized pH and environmental conditions, avoiding mutual interference between functional components, and enabling multiple mechanisms such as activation, mineralization, and cross-linking fixation to work synergistically. At the same time, comparing the data of Example 1 and Comparative Example 3 shows that the presence of synergistic functional molecule precursors enhances the antibacterial performance and stability of the final product.

[0121] Test Example 2: Fiber Physical Properties Test

[0122] To verify the effect of the preparation method described in the embodiments of the present invention on the original physical properties of cashmere fibers, the samples obtained in Examples 1-3, Comparative Example 1 and Comparative Example 4 were tested for breaking strength and softness.

[0123] The testing method is as follows:

[0124] Breaking strength test: conducted in accordance with GB / T-3923.1-2013 "Textiles - Tensile properties of fabrics - Part 1: Determination of breaking strength and elongation at break (strip method)".

[0125] Softness test: The test is conducted in accordance with GB / T-18318.1-2009 "Textiles - Determination of bending properties - Part 1: Inclined plane method". The softness of the fiber is characterized by the bending length. The smaller the bending length value, the softer the sample.

[0126] The experimental steps are as follows:

[0127] Sample preparation: Strip samples meeting the above standard requirements were prepared from the dried cashmere fiber samples obtained in Examples 1-3, Comparative Example 1 and Comparative Example 4.

[0128] Environmental conditioning: Condition all samples to be tested under standard atmospheric conditions (temperature 20±2℃, relative humidity 65±4%) for at least 24 hours.

[0129] Performance testing: Under the same standard atmospheric conditions, the breaking strength of the samples was determined using a tensile strength tester, and the bending length was determined using a fabric stiffness tester. Each group of samples was tested 10 times, and the results were averaged.

[0130] The experimental results are shown in Table 2:

[0131] The physical performance test results of each sample are recorded in Table 2.

[0132] Table 2: Physical property test results of each embodiment and comparative sample

[0133] sample Fracture strength (N) Bending length (mm) Example 1 376.8 24.6 Example 2 379.1 24.9 Example 3 374.2 24.4 Comparative Example 1 381.5 25.2 Comparative Example 4 312.7 28.8

[0134] Results Analysis: Table 2 and Appendix Figure 3 The data shows that the tensile strength values ​​of samples from Examples 1-3 are very close to those of Comparative Example 1 (untreated raw fibers), with a decrease of less than 3%. In contrast, the tensile strength of Comparative Example 4 (one-step treatment) decreased by more than 18%. This result indicates that the stepwise treatment process within a specific pH and temperature range used in this technical solution did not cause significant damage to the keratin matrix structure of cashmere fibers.

[0135] Meanwhile, from Table 2 and appendix Figure 4 The data shows that the bending length of samples 1-3 remained at a similar level or decreased slightly compared to the original fiber of Comparative Example 1, indicating that the fiber's softness was maintained. However, the bending length of sample 4 increased significantly, indicating that its fiber became stiffer. Combining the breaking strength and bending length indicators, this technology demonstrates that it can effectively maintain the fiber's original excellent physical properties while imparting functionality, while the mixed one-step treatment used in Comparative Example 4 negatively impacted the fiber's properties.

[0136] Test Example 3: Determination of the Immobilization Rate of Functional Components

[0137] To quantitatively evaluate the fixation effect of the preparation method described in the embodiments of the present invention on the functional components, the zinc content of the samples obtained in Example 1, Comparative Example 1 and Comparative Example 2 was determined, and the fixation rate of the functional components was calculated.

[0138] The testing method is as follows:

[0139] Test Principle: Zinc acetate is a key component in functional solutions, and its fixation on fibers directly reflects the overall fixation level of the functional components. By measuring the zinc content on the fibers before and after washing, the fixation rate of the functional components can be calculated.

[0140] Detection instrument: Inductively coupled plasma atomic emission spectrometer (ICP-AES).

[0141] Calculation formula: Functional component fixation rate (%) = (Zinc content of sample after washing / Zinc content of sample before washing) × 100%;

[0142] The experimental steps are as follows:

[0143] Sample preparation: Accurately weigh 0.1 g (accurate to 0.0001 g) of dried fiber samples from Example 1, Comparative Example 1, and Comparative Example 2, respectively. Each sample was divided into two groups: one group was the sample before washing, and the other group was washed 50 times according to GB / T-8629-2017 standard to obtain the sample after washing.

[0144] Sample digestion: Place the weighed sample in a polytetrafluoroethylene digestion vessel, add 5 mL of nitric acid and 2 mL of perchloric acid, and digest in a microwave digester. After digestion, place the digestion vessel on a hot plate to remove the acid until the contents are colorless and transparent or pale yellow.

[0145] Dilution of solution: Remove the cooled digestion vessel, wash the inner wall with deionized water in small amounts several times, and transfer all the washing solution to a 50mL volumetric flask. Finally, dilute to the mark with deionized water and shake well for later use.

[0146] Content determination: The zinc concentration in the test solution was determined using ICP-AES, and the zinc content (unit: mg / kg) in the fiber sample was calculated based on the sample weighing and the final volume.

[0147] The experimental results are shown in Table 3:

[0148] The results of the determination of zinc content and functional component fixation rate of each sample are recorded in Table 3.

[0149] Table 3: Results of Functional Component Fixation Rate Test for Each Sample

[0150] sample Zinc content before washing (mg / kg) Zinc content (mg / kg) after 50 washes Functional component fixation rate (%) Example 1 1258 1201 95.5 Comparative Example 1 Not detected Not detected - Comparative Example 2 1245 562 45.1

[0151] Results Analysis: The data in Table 3 show that after 50 cycles of washing, the functional component fixation rate of the sample in Example 1 reached 95.5%. No zinc was detected in the sample in Comparative Example 1 (raw fiber), confirming that the zinc in the test results all originated from the processing of this technical solution.

[0152] As attached Figure 5 As shown, the fixation rate of Comparative Example 2 (without transglutaminase) was only 45.1%, significantly lower than that of Example 1. This data quantitatively proves that the enzymatic cross-linking reaction in step six of this technical solution forms a stable cross-linking network between the keratin molecular chains of the fiber. This network structure effectively immobilizes the zinc-containing antibacterial components generated by in-situ mineralization within the fiber structure. This stable fixation mechanism is the basis for achieving excellent wash resistance and is consistent with the phenomenon in Test Example 1 where the sample of Example 1 still maintains a high antibacterial rate after washing.

[0153] Test Example 4: Cytotoxicity Test

[0154] To verify the biocompatibility of cashmere fibers after treatment by the preparation method described in the embodiments of the present invention, in vitro cytotoxicity tests were performed on the samples obtained in Example 1 and Comparative Example 1.

[0155] The testing method is as follows:

[0156] Testing standards: Based on GB / T-16886.5-2017 "Biological evaluation of medical devices - Part 5: In vitro cytotoxicity test".

[0157] Test method: Extraction solution method.

[0158] Cell line: L-929 mouse fibroblasts.

[0159] Evaluation metric: Relative cell growth rate (RGR), and cytotoxicity level determined according to standards. When RGR ≥ 75%, the cytotoxicity level is 0-1, indicating no cytotoxicity.

[0160] The experimental steps are as follows:

[0161] Preparation of extract: Under aseptic conditions, the fiber samples from Example 1 and Comparative Example 1 were immersed in MEM cell culture medium at a ratio of 0.1 g / mL. A blank culture medium without the samples was also provided as a negative control. The samples were extracted in an incubator at 37°C and 5% CO2 for 24 hours to prepare the extract.

[0162] Cell seeding: Logarithmic growth phase L-929 cells were seeded at an appropriate density in 96-well cell culture plates and cultured for 24 hours to allow them to adhere.

[0163] Sample preparation: Remove the original culture medium, and add the extract of each sample and the negative control solution to the culture wells, with 6 replicates per group. Continue culturing for 24 hours.

[0164] Toxicity evaluation: After incubation, MTT solution was added to each well, and incubation continued for 4 hours. The supernatant was then removed, and formazan crystals were dissolved in dimethyl sulfoxide (DMSO). The absorbance (OD) value of each well was measured at 490 nm using a microplate reader.

[0165] Results calculation: Relative cell proliferation rate (RGR, %) = [(OD sample - OD blank) / (OD negative control - OD blank)] × 100%.

[0166] The experimental results are shown in Table 4:

[0167] The in vitro cytotoxicity test results for each sample are recorded in Table 4.

[0168] Table 4: Results of in vitro cytotoxicity tests for each sample

[0169] sample Relative cell proliferation rate (RGR, %) Toxicity level Example 1 95.8 1 Comparative Example 1 98.3 0

[0170] Results Analysis: According to the GB / T-16886.5-2017 standard, materials with a cytotoxicity level of 0 or 1 were deemed non-cytotoxic. Table 4 shows that Comparative Example 1 (raw cashmere fiber) had a relative cell proliferation rate of 98.3% and a toxicity level of 0, consistent with its biocompatibility characteristics as a natural protein fiber.

[0171] The relative cell proliferation rate of the sample in Example 1 was 95.8%, and its toxicity level was Grade 1, which also falls within the category of non-cytotoxic. This result indicates that the nano-antibacterial cashmere fibers obtained after the series of steps included in this technical solution, such as activation complexation, biomimetic in-situ mineralization, and enzymatic cross-linking, did not exhibit potential cytotoxicity. This proves that the mild process conditions and functional system adopted in this technical solution, while endowing the fibers with durable antibacterial function, did not introduce substances that adversely affect cell survival, ensuring the biocompatibility and safety of the final product.

[0172] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing nano-antibacterial cashmere fiber, characterized in that, The preparation method comprises the following steps: S1. Immerse cashmere fibers in an activated complexing catalytic solution and treat them for 40 to 60 minutes at a pH of 5.5 to 6.5 and a temperature of 35 to 45°C. The activated complexing catalytic solution contains antibacterial metal salts, bioactive peptide inducers, and synergistic functional molecule precursors. S2. Without draining the liquid, add biomimetic in-situ mineralization solution to the bath solution in step S1, adjust the pH value of the bath solution to 8.5-9.5, and continue to treat for 20-40 minutes. S3. After washing the cashmere fibers treated in step S2, immerse them in an enzymatic cross-linking self-locking solution and treat them for 30 to 60 minutes at a pH of 6.0 to 7.0 and a temperature of 40 to 50°C. The enzymatic cross-linking self-locking solution contains transglutaminase.

2. The method for preparing nano-antibacterial cashmere fiber according to claim 1, characterized in that, The activated complexing catalyst solution comprises the following components in parts by weight: Antibacterial metal salt: 1.0–4.0 parts; Biological polypeptide inducer: 0.1–0.5 parts; Synergistic functional molecular precursor: 0.1–0.4 parts; Sodium citrate buffer: 0.5–2.0 parts; Deionized water: 100-200 parts.

3. The method for preparing nano-antibacterial cashmere fiber according to claim 2, characterized in that, The synergistic functional molecule precursor is (2,2-dimethyl-1,3-dioxolane-4-yl)methyl ester-5-(1,2-dithiopentane-3-yl)valerate, which is prepared by the following steps: α-Lipoic acid is esterified with a polyol under the action of a catalyst to generate a polyol ester of α-lipoic acid. The hydroxyl groups in the obtained polyol ester that did not participate in the esterification reaction were protected to obtain the (2,2-dimethyl-1,3-dioxolane-4-yl)methyl ester-5-(1,2-dithiopentane-3-yl)valerate.

4. The method for preparing nano-antibacterial cashmere fiber according to claim 2, characterized in that, The antibacterial metal salt is zinc acetate, and the biopeptide inducer is arginine-glycine-aspartic acid tripeptide.

5. The method for preparing nano-antibacterial cashmere fiber according to claim 1, characterized in that, In step S2, the biomimetic in-situ mineralization solution is prepared by dissolving sodium bicarbonate and glycerol in deionized water, wherein the amount of glycerol added is 1.0 to 3.0% of the dry weight of cashmere fibers.

6. The method for preparing nano-antibacterial cashmere fiber according to claim 1, characterized in that, In step S3, the enzyme activity concentration of transglutaminase in the enzymatic cross-linking self-locking solution is 10–30 U / mL.

7. The method for preparing nano-antibacterial cashmere fiber according to claim 1, characterized in that, In step S1, the metal ions in the antibacterial metal salt simultaneously serve as a precursor for the in-situ generation of nano-antibacterial particles and a catalyst for catalyzing the hydrolysis of the synergistic functional molecule precursor.

8. The method for preparing nano-antibacterial cashmere fiber according to claim 1, characterized in that, The preparation method further includes step S4: The cashmere fibers treated in step S3 are dried at a temperature of 75–85°C, and the drying process simultaneously inactivates the transglutaminase.

9. The method for preparing nano-antibacterial cashmere fiber according to claim 1, characterized in that, In step S3, the transglutaminase catalyzes the cross-linking of keratin molecular chains in cashmere fibers, thereby locking the nano-antibacterial particles generated in situ in step S2 and the synergistic functional molecules obtained by hydrolysis of the synergistic functional molecule precursor into the fiber interior.

10. The application of a nano-antibacterial cashmere fiber prepared by any one of claims 1-9 in the preparation of infant and toddler underwear, high-end functional clothing or medical and health textiles.

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