Tissue-like natural collagen composite absorbable suture and its preparation method and application

Abstract

This invention provides a tissue-like natural collagen composite absorbable suture, its preparation method, and its application, relating to biomedical materials. The invention provides a tissue-like natural collagen composite absorbable suture comprising medical-grade tissue-like natural collagen, epoxidized chitosan, molybdenum dioxide nanoparticles, and sodium alginate. The tissue-like natural collagen composite absorbable suture provided by this invention fully combines the advantageous functions of the components used, retaining the excellent mechanical properties and biodegradability of natural collagen composite materials, exhibiting low antigenicity and excellent antibacterial properties. It also incorporates the photothermal effect of molybdenum dioxide, resulting in a significant scar-reducing effect; it also possesses excellent fixation properties and can resist corrosion from bile, urine, and pancreatic juice, while promoting cell growth; it achieves the reuse of natural biological tissue, exhibiting excellent strength, antibacterial, and scar-reducing properties; the raw materials are widely available and low-cost, giving it a significant advantage in the field of medical suture materials.

Description

Technical Field

[0001] This invention relates to the field of biomedical materials technology, specifically to a tissue-like natural collagen composite absorbable suture, its preparation method, and its application. Background Technology

[0002] Sutures, as defined in surgical manuals, are specialized threads used for wound ligation, hemostasis, and tissue repair. Based on the biodegradability of their raw materials, they can be broadly categorized into non-absorbable sutures and absorbable sutures. Non-absorbable sutures typically do not degrade naturally within the body, requiring suture removal after suturing and often leaving scars on the suture surface. Absorbable sutures, on the other hand, degrade into soluble products within the body, generally being absorbed and excreted within 2-6 months. Absorbable sutures include natural fibers (such as catgut, silk, collagen, and chitin fibers) and synthetic polymer sutures. Ideally, absorbable sutures should possess good flexibility, high strength, good biocompatibility, ease of storage, and stable quality, allowing for thorough sterilization.

[0003] Collagen is a major component of mammalian skin, cartilage, ligaments, and other tissues. It possesses excellent biocompatibility, biodegradability, and absorbability, exhibits no foreign body reaction, and has low antigenicity, effectively promoting cell growth. It is also used as a material for absorbable sutures. However, current collagen-related products are primarily materials at the triple-helix molecular level, which offer significant advantages in tissue compatibility and tissue regeneration induction. However, the collagen tissue in traditional collagen products is prepared using degradation methods, which disrupt the aggregated structure of natural collagen, resulting in relatively rapid biodegradation and insufficient mechanical strength. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a tissue-like natural collagen composite absorbable suture, its preparation method, and its application. The tissue-like natural collagen composite absorbable suture provided by this invention possesses excellent mechanical properties, biodegradability, antibacterial properties, and scar-reducing effects; it also exhibits low antigenicity, low cost, and good fixation.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a tissue-like natural collagen composite absorbable suture, comprising medical-grade tissue-like natural collagen, epoxidized modified chitosan, molybdenum dioxide nanoparticles, and sodium alginate.

[0007] Preferably, the mass ratio of the tissue-like natural collagen to the epoxidized modified chitosan is 10:0.25-1.5;

[0008] The mass ratio of the medical-grade tissue natural collagen to molybdenum dioxide nanoparticles is 10:0.01-0.1;

[0009] The mass ratio of the medical-grade tissue natural collagen to sodium alginate is 10:0.25-1.5;

[0010] The molybdenum dioxide nanoparticles include monoclinic molybdenum dioxide nanoparticles.

[0011] Preferably, the method for preparing the medical-grade tissue-derived natural collagen includes the following steps:

[0012] (1) Remove the subcutaneous tissue from the animal skin, soak it in physiological saline, and obtain pretreated animal skin;

[0013] (2) The pretreated animal skin is degreased to obtain degreased animal skin;

[0014] (3) The defatted animal skin is subjected to hair removal treatment to obtain hairless animal skin;

[0015] (4) The hairless animal skin is subjected to a de-swelling treatment to obtain a de-swollen animal skin;

[0016] (5) The de-swelled animal skin is subjected to acid swelling treatment to obtain acid-swollen animal skin;

[0017] (6) The acid-swollen animal skin is crushed, the pH value is adjusted to 7-7.4, solid-liquid separation is performed to obtain solid components, the solid components are washed with water and dried to obtain medical-grade tissue natural collagen.

[0018] Preferably, in step (2), the degreasing treatment includes: adding a degreasing agent and water to the pretreated animal skin for degreasing treatment;

[0019] The mass ratio of the pretreated animal hide to the defatting agent is 1:0.01 to 0.04;

[0020] The degreasing agent includes one or more of alkyl polyglycosides, phenacetin, laundry detergent, sodium lauryl sulfate, and fatty alcohol polyoxyethylene ether;

[0021] The mass-to-volume ratio of the pretreated animal hide to water is 1 kg: 1.5–3 L;

[0022] The degreasing treatment is performed at a temperature of 30–37°C for 2–5 hours.

[0023] The degreasing process also includes washing with water;

[0024] In step (3), the hair removal treatment includes: adding the defatted animal skin, water, polyoxyethylene ether and ferrous salt for the first hair removal treatment, adding alkaline amine for the second hair removal treatment, adding alkaline reagent for the third hair removal treatment, adding oxidant for the fourth hair removal treatment, and adding dilute alkaline reagent aqueous solution for the fifth hair removal treatment.

[0025] The mass-to-volume ratio of the defatted animal skin to water is 1 kg: 1-2 L;

[0026] The polyoxyethylene ether includes fatty alcohol polyoxyethylene ether and / or nonylphenol polyoxyethylene ether; the mass ratio of the pretreated animal skin to the polyoxyethylene ether is 1:0.3-0.6;

[0027] The ferrous salt includes ferrous sulfate and / or ferrous ammonium sulfate; the mass ratio of the pretreated animal skin to the ferrous salt is 1:0.3-0.6;

[0028] The first hair removal treatment lasts for 90–150 minutes;

[0029] The alkanolamine includes one or more of triethanolamine, monoethanolamine, and diethanolamine; the mass ratio of the pretreated animal skin to the alkanolamine is 1:0.01 to 0.03.

[0030] The second hair removal treatment takes 10–20 minutes;

[0031] The alkaline reagent includes alkali metal hydroxides and / or alkali metal carbonates; the mass ratio of the pretreated animal skin to the alkaline reagent is 1:0.035 to 0.045;

[0032] The third hair removal treatment takes 15–25 minutes;

[0033] The oxidant includes one or more of hydrogen peroxide, sodium perborate, and sodium percarbonate; the mass ratio of the pretreated animal skin to the oxidant is 1:0.06 to 0.08.

[0034] The fourth hair removal treatment takes 3 to 4 hours;

[0035] The alkaline reagent in the dilute alkaline aqueous solution includes alkali metal hydroxides and / or alkali metal carbonates; the mass fraction of the dilute alkaline reagent aqueous solution is 0.3-0.8%; the duration of the fifth hair removal treatment is 4-6 hours.

[0036] The hair removal process also includes washing with water;

[0037] In step (4), the swelling removal treatment includes: adding a first portion of water and inorganic salts to the dehaired animal skin for a first swelling removal treatment, adding a second portion of water to adjust the pH value to 4-4.5, adding acidic lipase for a second swelling removal treatment, and adding acidic protease for a third swelling removal treatment.

[0038] The mass-to-volume ratio of the pretreated animal hide to the first portion of water is 1 kg: 0.8–1 L;

[0039] The inorganic salt includes one or more of sodium bisulfite, ammonium sulfate, ammonium chloride, and ammonium acetate; the inorganic salt accounts for 0.05-0.2% of the mass of the pretreated animal skin.

[0040] The temperature of the first deswelling treatment was 28–35°C, the time was 50–60 min, and the final pH value was 8–8.5;

[0041] The mass-to-volume ratio of the pretreated animal hide to the second portion of water is 1 kg: 1-4 L;

[0042] The acidic lipase comprises 0.1-0.3% of the pretreated animal skin by mass; the enzyme activity of the acidic lipase is 50,000-60,000 units / g.

[0043] The second deswelling treatment is performed at a temperature of 28–35°C for 15–20 minutes.

[0044] The acidic protease comprises 0.1–0.3% of the pretreated animal skin by mass; the enzyme activity of the acidic protease is 80,000–100,000 units / g.

[0045] The third deswelling treatment is performed at a temperature of 38–42°C for 2–5 hours.

[0046] The swelling reduction treatment also includes washing with water;

[0047] In step (5), the acid swelling treatment includes: adding water to the de-swelled animal skin, adjusting the pH value to 2.8-3.0, stirring the acid swelling treatment, and then letting it stand for acid swelling treatment;

[0048] The mass-to-volume ratio of the pretreated animal hide to water is 1 kg: 1-2 L;

[0049] The stirring acid swelling treatment time is 30-60 minutes;

[0050] The static acid swelling treatment time is 6-8 hours;

[0051] The acid swelling treatment also includes washing with water.

[0052] In step (6), the crushing includes ball milling, wherein the ball-to-material ratio of the ball milling is 1:1 to 5, the rotation speed is 200 to 600 r / min, and the time is 1 to 3 h;

[0053] The drying includes freeze drying;

[0054] The drying process also includes disinfection and sterilization.

[0055] Preferably, the epoxidized chitosan comprises epoxidized chitosan obtained by epoxidizing chitosan with ethylene glycol diglycidyl ether.

[0056] Preferably, the preparation method of the epoxidized modified chitosan includes the following steps:

[0057] Chitosan, ethylene glycol diglycidyl ether, and water were mixed and epoxidized to obtain epoxidized chitosan.

[0058] This invention also provides a method for preparing the tissue-like natural collagen composite absorbable suture described in the above technical solution, comprising the following steps:

[0059] Medical-grade tissue natural collagen, epoxidized chitosan, molybdenum dioxide nanoparticles, sodium alginate and water were blended to obtain a spinning solution.

[0060] The spinning solution is spun to obtain a tissue-like natural collagen composite absorbable suture.

[0061] Preferably, the mass ratio of the tissue-like natural collagen to the epoxidized modified chitosan is 10:0.25-1.5;

[0062] The mass ratio of the medical-grade tissue natural collagen to molybdenum dioxide nanoparticles is 10:0.01-0.1;

[0063] The mass ratio of the medical-grade tissue natural collagen to sodium alginate is 10:0.25-1.5;

[0064] The concentration of medicinal grade tissue natural collagen in the spinning solution is 12-25 wt%.

[0065] Preferably, the spinning process conditions include: the coagulation bath is saturated sodium sulfate; the pressure is 0.05-0.2 MPa; the spinning solution temperature is room temperature; the coagulation temperature is 25-35℃; and the winding speed is 8-15 m / min.

[0066] The present invention also provides the application of the tissue-like natural collagen composite absorbable suture described in the above technical solution or the tissue-like natural collagen composite absorbable suture prepared by the preparation method described in the above technical solution in tissue engineering, regenerative medicine materials or implantable medical devices.

[0067] This invention utilizes medical-grade tissue-like natural collagen, a material that possesses excellent biocompatibility, suitable biodegradability, good mechanical properties, and superior thermal and structural stability. It exhibits low antigenicity and ease of preservation, while also providing rapid and effective hemostasis, promoting wound healing and repair. It is an ideal material for biomedical applications, fundamentally solving the problems of rapid biodegradation and insufficient mechanical strength inherent in collagen molecular-level materials or gelatin materials. This invention further enhances the material by adding epoxidized chitosan, which inhibits the growth and reproduction of various bacteria and fungi, promotes skin regeneration, and accelerates wound healing after suturing.

[0068] Molybdenum dioxide, as a metallic semiconductor, has excellent electrical conductivity. This invention, by adding molybdenum dioxide nanoparticles, can not only improve the conductivity of tissue-like natural collagen composite absorbable sutures and further enhance their wear resistance and anti-slip properties, but also bring about a significant scar removal effect due to the photothermal effect of molybdenum dioxide.

[0069] The sodium alginate added in this invention is a linear polysaccharide with excellent biocompatibility, biodegradability, non-toxicity, and low raw material cost. Chitosan and its derivatives have broad-spectrum antibacterial effects, inhibiting the reproduction and growth of various bacteria and fungi, and are non-toxic and have strong antibacterial properties. Wound dressings with added chitosan can prevent bacterial penetration, promote skin regeneration, and accelerate wound healing, in addition to their good biocompatibility, strength, flexibility, and bioabsorbability.

[0070] The natural collagen composite absorbable suture provided by this invention is composed of collagen, chitosan, molybdenum dioxide nanoparticles, and sodium alginate. It boasts a wider range of sources, lower cost, and achieves efficient utilization of natural biomaterials. This tissue-like natural collagen composite absorbable suture fully combines the advantageous functions of each component, retaining the excellent mechanical and biodegradability of natural collagen composite materials, exhibiting low antigenicity and excellent antibacterial properties. It also incorporates the photothermal effect of molybdenum dioxide, resulting in a significant scar-reducing effect. Furthermore, it possesses excellent fixation properties and can resist corrosion from bile, urine, and pancreatic juice, while promoting cell growth. The adsorption bonds formed between different components further ensure the strength of the natural collagen composite absorbable suture and endow it with superior antibacterial and scar-reducing properties.

[0071] The method for preparing natural collagen composite absorbable sutures provided by this invention has the advantages of wide availability of raw materials, simple process, low production cost, short production cycle, and green and environmentally friendly preparation process. The tissue-like natural collagen composite absorbable sutures prepared by this method have excellent mechanical properties and biodegradability, low antigenicity and low cost, and also have good fixation properties. Attached Figure Description

[0072] Figure 1 This is a photograph of the tissue-like natural collagen composite absorbable suture prepared in Example 1;

[0073] Figure 2 This is a photograph of the tissue-like natural collagen composite absorbable suture prepared in Example 2;

[0074] Figure 3 This is a photograph of the tissue-like natural collagen composite absorbable suture prepared in Example 3;

[0075] Figure 4 MTT assay results for collagen, antigen-free collagen aggregates prepared in Comparative Example 1, and medical-grade tissue-like natural collagen prepared in Example 4;

[0076] Figure 5 This is a 24-hour scratch test result image of collagen.

[0077] Figure 6 The scratch results of antigen-free collagen aggregates prepared in Comparative Example 1 after 24 hours are shown.

[0078] Figure 7 The image shows the 24-hour scratch results of the medical-grade tissue natural collagen prepared in Example 4. Detailed Implementation

[0079] This invention provides a tissue-like natural collagen composite absorbable suture, comprising medical-grade tissue-like natural collagen, epoxidized modified chitosan, molybdenum dioxide nanoparticles, and sodium alginate.

[0080] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0081] In this invention, the preferred mass ratio of the tissue-like natural collagen to the epoxidized chitosan is 10:0.25 to 1.5, and in specific embodiments, it can be 10:0.25, 10:0.5, 10:0.75, 10:1, 10:1.25, or 10:1.5. In this invention, the epoxidized chitosan preferably comprises epoxidized chitosan obtained by epoxidizing chitosan with ethylene glycol diglycidyl ether, and the epoxidized chitosan preferably has the structure shown in Formula I, where n is 2 to 10, and in specific embodiments, it can be 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0082]

[0083] In this invention, tissue-like natural collagen possesses excellent biocompatibility, suitable biodegradability, good mechanical properties, and superior thermal and structural stability. It also exhibits low antigenicity and ease of preservation, and can rapidly and effectively stop bleeding, promote wound healing, and facilitate repair, making it an ideal material for biomedical applications. The tissue-like natural collagen used in this invention fundamentally solves the problems of insufficient biodegradability and mechanical strength inherent in collagen molecular-level materials or gelatin materials.

[0084] This invention uses epoxidized chitosan to supplement and modify tissue-like natural collagen composite absorbable sutures. The enhanced composite fibers inhibit the growth of various bacteria and fungi, promote skin regeneration, and accelerate wound healing after suturing.

[0085] In this invention, the preferred mass ratio of medical-grade tissue-derived natural collagen to molybdenum dioxide nanoparticles is 10:0.01 to 0.1, and in specific embodiments, it can be 10:0.01, 10:0.02, 10:0.03, 10:0.04, 10:0.05, 10:0.06, 10:0.07, 10:0.08, 10:0.09, or 10:0.1. In this invention, the molybdenum dioxide nanoparticles include monoclinic molybdenum dioxide nanoparticles. Molybdenum dioxide, as a metallic semiconductor, possesses excellent electrical conductivity. By adding molybdenum dioxide nanoparticles, this invention not only improves the conductivity of sutures and further enhances the wear resistance and anti-slip properties of spun fibers, but also, the photothermal effect of molybdenum dioxide can bring about a significant scar-reducing effect.

[0086] In this invention, the preferred mass ratio of medical-grade tissue-derived natural collagen to sodium alginate is 10:0.25 to 1.5, and in specific embodiments, it can be 10:0.25, 10:0.5, 10:0.75, 10:1, 10:1.25, or 10:1.5. The sodium alginate added in this invention is a linear polysaccharide with excellent biocompatibility, biodegradability, non-toxicity, and low raw material cost, and has wide applications in the fields of medicine, food, and cosmetics.

[0087] In this invention, the cross-section of the tissue-like natural collagen composite absorbable suture is preferably circular. The tissue-like natural collagen composite absorbable suture provided by this invention fully combines the advantageous functions of the components used, retaining the excellent mechanical properties and biodegradability of natural collagen composite materials, exhibiting low antigenicity and excellent antibacterial properties; it also incorporates the photothermal effect of molybdenum dioxide, resulting in a significant scar-reducing effect; it also possesses excellent fixation properties, while resisting corrosion from bile, urine, and pancreatic juice, and promoting cell growth.

[0088] The preparation method of medical-grade tissue natural collagen is described in detail below.

[0089] In this invention, the method for preparing the medical-grade tissue-derived natural collagen includes the following steps:

[0090] (1) Remove the subcutaneous tissue from the animal skin, soak it in physiological saline, and obtain pretreated animal skin;

[0091] (2) The pretreated animal skin is degreased to obtain degreased animal skin;

[0092] (3) The defatted animal skin is subjected to hair removal treatment to obtain hairless animal skin;

[0093] (4) The hairless animal skin is subjected to a de-swelling treatment to obtain a de-swollen animal skin;

[0094] (5) The de-swelled animal skin is subjected to acid swelling treatment to obtain acid-swollen animal skin;

[0095] (6) The acid-swollen animal skin is crushed, the pH value is adjusted to 7-7.4, solid-liquid separation is performed to obtain solid components, the solid components are washed with water and dried to obtain medical-grade tissue natural collagen.

[0096] This invention removes the subcutaneous tissue from animal skin, soaks it in physiological saline, and obtains pretreated animal skin.

[0097] In this invention, the animal skin preferably includes one or more of the animal skins of pigs, cattle, and sheep; the animal skin is preferably fresh and traceable.

[0098] This invention preferably involves first cleaning and soaking the animal skin in water, and then removing the subcutaneous tissue. In this invention, the purpose of cleaning is to remove dirt from the animal skin. In this invention, the water soaking temperature is preferably room temperature, and the soaking time is preferably 60–120 minutes, but in specific embodiments it can be 60 minutes, 70 minutes, 80 minutes, 90 minutes, 100 minutes, 110 minutes, or 120 minutes. In this invention, the method of removing the subcutaneous tissue from the animal skin preferably includes mechanical desquamation; the subcutaneous tissue includes subcutaneous fat, surface muscle, blood vessels, and fascia.

[0099] In this invention, the animal skin, after removing the subcutaneous tissue, is first cut into pieces, washed with physiological saline, and then soaked in physiological saline. In this invention, the size of the animal pieces obtained from the cutting is preferably 5-10 mm × 5-10 mm. In this invention, the temperature of the physiological saline soaking is preferably room temperature, and the soaking time is preferably 10-18 hours, which can be 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, or 18 hours in specific embodiments.

[0100] After obtaining the pretreated animal skin, the present invention performs a defatting treatment on the pretreated animal skin to obtain defatted animal skin.

[0101] In this invention, the defatting treatment preferably includes: adding a defatting agent and water to the pretreated animal skin for defatting treatment;

[0102] In this invention, the preferred mass-to-volume ratio of the pretreated animal skin to water is 1 kg: 1.5 to 3 L. In specific embodiments, it can be 1 kg: 1.5 L, 1 kg: 1.6 L, 1 kg: 1.7 L, 1 kg: 1.8 L, 1 kg: 1.9 L, 1 kg: 2 L, 1 kg: 2.1 L, 1 kg: 2.2 L, 1 kg: 2.3 L, 1 kg: 2.4 L, 1 kg: 2.5 L, 1 kg: 2.6 L, 1 kg: 2.7 L, 1 kg: 2.8 L, 1 kg: 2.9 L, or 1 kg: 3 L.

[0103] In this invention, the degreasing agent preferably includes one or more of alkyl polyglycosides, sulfadiazine, laundry detergent, sodium lauryl sulfate, and fatty alcohol polyoxyethylene ether. In this invention, the mass ratio of the pretreated animal skin to the degreasing agent is preferably 1:0.01 to 0.04, and in specific embodiments it can be 1:0.01, 1:0.015, 1:0.02, 1:0.025, 1:0.03, 1:0.035, or 1:0.04.

[0104] In this invention, the temperature of the degreasing treatment is preferably 30-37°C, and in specific embodiments it can be 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C or 37°C; the time of the degreasing treatment is preferably 2-5 hours, and in specific embodiments it can be 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours; the degreasing treatment is preferably carried out in a rotating drum; the rotation speed of the rotating drum is preferably 5-12 r / min, and in specific embodiments it can be 5 r / min, 6 r / min, 7 r / min, 8 r / min, 9 r / min, 10 r / min, 11 r / min or 12 r / min.

[0105] In this invention, the degreasing treatment preferably further includes washing the degreased animal hide with water to obtain degreased animal hide. In this invention, the number of washes is preferably 3 to 5 times, more preferably 4 times; the temperature of the water used for washing is preferably the same as the temperature of the degreasing treatment.

[0106] After obtaining defatted animal hides, the present invention performs hair removal treatment on the defatted animal hides to obtain hairless animal hides.

[0107] In this invention, the hair removal treatment preferably includes: a first hair removal treatment by adding the defatted animal skin, water, polyoxyethylene ether, and ferrous salt; a second hair removal treatment by adding an alkaline amine; a third hair removal treatment by adding an alkaline reagent; a fourth hair removal treatment by adding an oxidizing agent; and a fifth hair removal treatment by adding a dilute alkaline aqueous solution. In this invention, the hair removal treatment temperature is preferably room temperature, and the hair removal treatment is preferably carried out in a rotating drum; the rotation speed of the drum is preferably 5–12 r / min, and in specific embodiments it can be 5 r / min, 6 r / min, 7 r / min, 8 r / min, 9 r / min, 10 r / min, 11 r / min, or 12 r / min.

[0108] In this invention, the preferred mass ratio of defatted animal skin to water is 1 kg: 1-2 L. In specific embodiments, it can be 1 kg: 1 L, 1 kg: 1.1 L, 1 kg: 1.2 L, 1 kg: 1.3 L, 1 kg: 1.4 L, 1 kg: 1.5 L, 1 kg: 1.6 L, 1 kg: 1.7 L, 1 kg: 1.8 L, 1 kg: 1.9 L, or 1 kg: 2 L.

[0109] In this invention, the polyoxyethylene ether preferably includes fatty alcohol polyoxyethylene ether and / or nonylphenol polyoxyethylene ether. In this invention, the mass ratio of the pretreated animal skin to the polyoxyethylene ether is preferably 1:0.3 to 0.6, and in specific embodiments it can be 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5, 1:0.55, or 1:0.6.

[0110] In this invention, the ferrous salt preferably includes ferrous sulfate and / or ferrous ammonium sulfate. In this invention, the mass ratio of the pretreated animal skin to the ferrous salt is preferably 1:0.3 to 0.6, and in specific embodiments it can be 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5, 1:0.55, or 1:0.6.

[0111] In this invention, the preferred time for the first hair removal treatment is 90 to 150 minutes, and in specific embodiments it can be 90 minutes, 100 minutes, 110 minutes, 120 minutes, 130 minutes, 140 minutes or 150 minutes.

[0112] In this invention, the alkanolamine preferably includes one or more of triethanolamine, monoethanolamine, and diethanolamine. In this invention, the mass ratio of the pretreated animal skin to the alkanolamine is preferably 1:0.01 to 0.03, and in specific embodiments it can be 1:0.01, 1:0.015, 1:0.02, 1:0.025, or 1:0.03.

[0113] In this invention, the second hair removal treatment time is preferably 10 to 20 minutes, and in specific embodiments it can be 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes or 20 minutes.

[0114] In this invention, the alkaline reagent preferably comprises alkali metal hydroxides and / or alkali metal carbonates; the alkali metal hydroxides preferably comprise sodium hydroxide and / or potassium hydroxide; and the alkali metal carbonates preferably comprise sodium carbonate and / or potassium carbonate. In this invention, the mass ratio of the pretreated animal skin to the alkaline reagent is preferably 1:0.035 to 0.045, and in specific embodiments it can be 1:0.035, 1:0.036, 1:0.037, 1:0.038, 1:0.039, 1:0.04, 1:0.041, 1:0.042, 1:0.043, 1:0.044, or 1:0.045.

[0115] In this invention, the time for the third hair removal treatment is preferably 15 to 25 minutes, and in specific embodiments it can be 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes, 20 minutes, 21 minutes, 22 minutes, 23 minutes, 24 minutes or 25 minutes.

[0116] In this invention, the oxidant preferably includes one or more of hydrogen peroxide, sodium perborate, and sodium percarbonate; the mass concentration of the hydrogen peroxide is preferably 1-30%, and in specific embodiments it can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 10%, 15%, 20%, 25%, or 30%. In this invention, the preferred mass ratio of the pretreated animal skin to the oxidant is 1:0.06 to 0.08. In specific embodiments, it can be 1:0.061, 1:0.062, 1:0.063, 1:0.064, 1:0.065, 1:0.066, 1:0.067, 1:0.068, 1:0.069, 1:0.07, 1:0.071, 1:0.072, 1:0.073, 1:0.074, 1:0.075, 1:0.076, 1:0.077, 1:0.078, 1:0.079, or 1:0.08.

[0117] In this invention, the preferred time for the fourth hair removal treatment is 3 to 4 hours, and in specific embodiments it can be 180 min, 190 min, 200 min, 210 min, 220 min, 230 min or 240 min.

[0118] In this invention, the mass fraction of the dilute alkaline reagent aqueous solution is preferably 0.3% to 0.8%, and in specific embodiments it can be 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, or 0.8%. In this invention, the alkaline reagent in the dilute alkaline reagent aqueous solution preferably includes alkali metal hydroxides and / or alkali metal carbonates; the alkali metal hydroxides preferably include sodium hydroxide and / or potassium hydroxide; the alkali metal carbonates preferably include sodium carbonate and / or potassium carbonate. This invention does not have a special limitation on the amount of the dilute alkaline reagent aqueous solution; it only needs to be sufficient to submerge the animal skin after the fourth hair removal treatment.

[0119] In this invention, the fifth hair removal treatment time is preferably 4 to 6 hours, and in specific embodiments it can be 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours.

[0120] In this invention, the hair removal process preferably further includes washing the treated animal skin with water to obtain a hairless animal skin. In this invention, the number of washes is preferably 3 to 5 times, more preferably 4 times.

[0121] After obtaining the hairless animal skin, the present invention performs a de-swelling treatment on the hairless animal skin to obtain a de-swelled animal skin.

[0122] In this invention, the deswelling treatment preferably includes: adding a first portion of water and inorganic salts to the dehaired animal skin for a first deswelling treatment; adding a second portion of water to adjust the pH value to 4-4.5; adding acidic lipase for a second deswelling treatment; and adding acidic protease for a third deswelling treatment. The deswelling treatment is preferably carried out in a drum. The rotation speed of the drum is preferably 5-10 r / min, and in specific embodiments it can be 5 r / min, 6 r / min, 7 r / min, 8 r / min, 9 r / min or 10 r / min.

[0123] In this invention, the preferred mass-to-volume ratio of the pretreated animal skin to the first portion of water is 1 kg: 0.8 to 1 L. In specific embodiments, it can be 1 kg: 0.8 L, 1 kg: 0.85 L, 1 kg: 0.9 L, 1 kg: 0.95 L, or 1 kg: 1 L.

[0124] In this invention, the inorganic salt preferably includes one or more of sodium bisulfite, ammonium sulfate, ammonium chloride, and ammonium acetate; the mass of the inorganic salt preferably accounts for 0.05-0.2% of the mass of the pretreated animal skin, and in specific embodiments it can be 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%.

[0125] In this invention, the temperature of the first deswelling treatment is preferably 28-35°C, and in specific embodiments it can be 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C or 35°C; the time of the first deswelling treatment is preferably 50-60 min, and in specific embodiments it can be 50 min, 51 min, 52 min, 53 min, 54 min, 55 min, 56 min, 57 min, 58 min, 59 min or 60 min; the endpoint pH value of the first deswelling treatment is preferably 8-8.5, and in specific embodiments the endpoint pH value can be 8, 8.1, 8.2, 8.3, 8.4 or 8.5.

[0126] In this invention, the preferred mass-to-volume ratio of the pretreated animal skin to the second portion of water is 1 kg: 1 to 4 L. In specific embodiments, it can be 1 kg: 1 L, 1 kg: 1.1 L, 1 kg: 1.2 L, 1 kg: 1.5 L, 1 kg: 2 L, 1 kg: 2.5 L, 1 kg: 3 L, 1 kg: 3.5 L, or 1 kg: 4 L.

[0127] In this invention, the acidic lipase preferably accounts for 0.1% to 0.3% of the mass of the pretreated animal skin. In specific embodiments, it can be 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, or 0%. 0.27%, 0.28%, 0.29%, or 0.3%; the enzyme activity of the acid lipase is preferably 50,000 to 60,000 units / g, and in specific embodiments it can be 50,000 units / g, 51,000 units / g, 50,000 units / g, 53,000 units / g, 54,000 units / g, 55,000 units / g, 56,000 units / g, 57,000 units / g, 58,000 units / g, 59,000 units / g, or 60,000 units / g;

[0128] In this invention, the temperature of the second deswelling treatment is preferably 28-35°C, and in specific embodiments it can be 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C or 35°C; the time of the second deswelling treatment is preferably 15-20 min, and in specific embodiments it can be 15 min, 16 min, 17 min, 18 min, 19 min or 20 min.

[0129] In this invention, the acidic protease accounts for 0.1-0.3% of the mass of the pretreated animal skin. In specific embodiments, this can be 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, or 0.3%. The enzyme activity of the acidic protease is preferably 80,000-100,000 units / g. In specific embodiments, the concentrations can be 80,000 units / g, 81,000 units / g, 82,000 units / g, 83,000 units / g, 84,000 units / g, 85,000 units / g, 86,000 units / g, 87,000 units / g, 88,000 units / g, 89,000 units / g, 90,000 units / g, 91,000 units / g, 92,000 units / g, 93,000 units / g, 94,000 units / g, 95,000 units / g, 96,000 units / g, 97,000 units / g, 98,000 units / g, 99,000 units / g, or 100,000 units / g.

[0130] In this invention, the temperature of the third de-swelling treatment is preferably 38-42°C, and in specific embodiments it can be 38°C, 39°C, 40°C, 41°C or 42°C; the time of the third de-swelling treatment is preferably 2-5 hours, and in specific embodiments it can be 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours.

[0131] In this invention, the process of removing swelling preferably further includes washing the treated animal skin with water to obtain a de-swollen animal skin. In this invention, the number of washes is preferably 3 to 5 times, more preferably 4 times.

[0132] After obtaining the de-swelled animal skin, the present invention performs acid swelling treatment on the de-swelled animal skin to obtain acid-swelled animal skin.

[0133] In this invention, the acid swelling treatment preferably includes: adding water to the de-swelled animal skin, adjusting the pH value to 2.8-3.0, stirring for acid swelling treatment, and then allowing it to stand for acid swelling treatment; the temperature of the acid swelling treatment is preferably room temperature, and the acid swelling treatment is preferably carried out in a drum; the rotation speed of the drum is preferably 5-12 r / min, and in specific embodiments it can be 5 r / min, 6 r / min, 7 r / min, 8 r / min, 9 r / min, 10 r / min, 11 r / min or 12 r / min.

[0134] In this invention, the preferred mass-to-volume ratio of the pretreated animal skin to water is 1 kg: 1-2 L. In specific embodiments, it can be 1 kg: 1 L, 1 kg: 1.1 L, 1 kg: 1.2 L, 1 kg: 1.3 L, 1 kg: 1.4 L, 1 kg: 1.5 L, 1 kg: 1.6 L, 1 kg: 1.7 L, 1 kg: 1.8 L, 1 kg: 1.9 L, or 1 kg: 2 L.

[0135] In this invention, the acid used to adjust the pH value to 2.8-3.0 preferably includes formic acid solution and / or sulfuric acid solution; the mass concentration of the formic acid solution is preferably 0.05-0.08%, and in specific embodiments it can be 0.05%, 0.06%, 0.07% or 0.08%; the mass concentration of the sulfuric acid solution is preferably 0.08-0.12%, and in specific embodiments it can be 0.08%, 0.09%, 0.010%, 0.011% or 0.012%; when the acid is a mixed acid solution of formic acid solution and sulfuric acid solution, the volume ratio of formic acid solution to sulfuric acid solution in the mixed acid solution is preferably 1:2-3, more preferably 1:2.5.

[0136] In this invention, the stirring acid swelling treatment time is preferably 30 to 60 minutes, and in specific embodiments it can be 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes or 60 minutes.

[0137] In this invention, the preferred time for the static acid swelling treatment is 6 to 8 hours, and in specific embodiments it can be 6 hours, 6.5 hours, 7 hours, 7.5 hours or 8 hours.

[0138] In this invention, the acid swelling treatment preferably further includes washing the acid-swollen animal skin with water to obtain acid-swollen animal skin. In this invention, the number of water washes is preferably 3 to 5 times, more preferably 4 times.

[0139] After obtaining the acid-swollen animal skin, the present invention pulverizes the acid-swollen animal skin, adjusts the pH value to 7-7.4, separates the solid and liquid components to obtain solid components, washes the solid components with water and dries them to obtain medical-grade tissue natural collagen.

[0140] In this invention, the pulverization preferably includes ball milling. In this invention, the ball-to-material ratio in the ball milling is preferably 1:1 to 5, and in specific embodiments it can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, or 1:5; the ball milling speed is preferably 200 to 600 r / min, and in specific embodiments it can be 200 r / min, 300 r / min, 400 r / min, 500 r / min, or 600 r / min; the ball milling time is preferably 1 to 3 hours, and in specific embodiments it can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours. In this invention, the grinding media used in the ball mill preferably include large balls and small balls; the particle size of the large balls is preferably 12-13 mm; the particle size of the small balls is preferably 9-10 mm; the ratio of the number of large balls to small balls is preferably 1:1-3, and in specific embodiments it can be 1:1, 1:1.5, 1:2, 1:2.5 or 1:3.

[0141] After ball milling, the present invention preferably further includes centrifuging the ball-milled system to remove the supernatant, collecting the slurry, and then adjusting the pH of the slurry to 7-7.4. In the present invention, the centrifugation speed is preferably 15000-18000 r / min, and in specific embodiments it can be 15000 r / min, 16000 r / min, 17000 r / min, or 18000 r / min; the centrifugation time is preferably 10-15 min, and in specific embodiments it can be 10 min, 11 min, 12 min, 13 min, 14 min, or 15 min.

[0142] In this invention, the alkali used to adjust the pH value to 7-7.4 preferably includes one or more of hydroxides, carbonates, and bicarbonates. The hydroxides preferably include one or more of sodium hydroxide, potassium hydroxide, and calcium hydroxide. The carbonates preferably include sodium carbonate and / or potassium carbonate. The alkali metal bicarbonates preferably include one or more of sodium bicarbonate, potassium bicarbonate, and calcium bicarbonate. In specific embodiments, the pH value can be 7, 7.1, 7.2, 7.3, or 7.4.

[0143] In this invention, the solid-liquid separation preferably includes centrifugal separation, and the centrifugal separation speed is preferably 15000-18000 r / min, which can be 15000 r / min, 16000 r / min, 17000 r / min or 18000 r / min in specific embodiments; the centrifugal separation time is preferably 10-15 min, which can be 10 min, 11 min, 12 min, 13 min, 14 min or 15 min in specific embodiments.

[0144] In this invention, the drying preferably includes freeze drying. This invention does not have any special limitations on the conditions for freeze drying; freeze drying is sufficient.

[0145] In this invention, the drying process preferably further includes sterilizing the dried natural collagen to obtain medical-grade tissue natural collagen. In this invention, the sterilization is preferably performed using gamma rays; the dose of the gamma rays is preferably 6–25 kGy / h60Co, and in specific embodiments can be 6 kGy / h60Co, 7 kGy / h60Co, 8 kGy / h60Co, 9 kGy / h60Co, 10 kGy / h60Co, 11 kGy / h60Co, 12 kGy / h60Co, or 3 kGy / h60Co. Co、14KGy / h60Co、15KGy / h60Co、16KGy / h60Co、17KGy / h60Co、18KGy / h60Co、19KGy / h60C o, 20KGy / h60Co, 21KGy / h60Co, 22KGy / h60Co, 23KGy / h60Co, 24KGy / h60Co or 25KGy / h60Co.

[0146] This invention provides a method for preparing medical-grade tissue-derived natural collagen. The process is simple, requires minimal equipment, uses abundant raw materials, is low-cost, and is easily scalable for industrial production. The medical-grade tissue-derived natural collagen prepared by this invention undergoes no degradation of natural collagen; its basic composition is the same as that of natural collagen in tissues—collagen fiber bundles—and it also possesses the spatial structural characteristics of natural collagen in tissues, allowing it to more closely mimic the structure of natural tissues. The medical-grade tissue-derived natural collagen prepared by this invention exhibits superior mechanical properties, excellent enzyme / thermal stability, and structural stability. It has low antigenicity and is easier to preserve, possesses excellent hemostatic properties, and its high strength and toughness can meet the diverse performance requirements of the body, making it an ideal collagen biomedical material. The medical-grade tissue-derived natural collagen prepared by this invention promotes cell survival, proliferation, and differentiation, and in wound and scar repair, it can significantly promote tissue regeneration and repair, reducing scar formation.

[0147] The preparation method of epoxidized chitosan is described in detail below.

[0148] In this invention, the preparation method of the epoxidized chitosan includes the following steps: mixing chitosan, ethylene glycol diglycidyl ether, and water, and then performing epoxidation modification to obtain epoxidized chitosan. The reaction route is as follows:

[0149]

[0150] In this invention, the mixing preferably includes: suspending chitosan in water, heating, and adding an aqueous solution of ethylene glycol diglycidyl ether dropwise.

[0151] In this invention, the chitosan is preferably used in the form of chitosan powder. In this invention, the mass-to-volume ratio of chitosan to water is preferably 2g:20-25mL, and in specific embodiments it can be 2g:20mL, 2g:21mL, 2g:22mL, 2g:23mL, 2g:24mL, or 2g:25mL.

[0152] In this invention, the temperature after heating is preferably 95-100°C, and in specific embodiments it can be 95°C, 96°C, 97°C, 98°C, 99°C or 100°C.

[0153] In this invention, the preferred mass ratio of chitosan to the aqueous solution of ethylene glycol diglycidyl ether is 2:0.5 to 5, and in specific embodiments, it can be 2:0.5, 2:1, 2:1.5, 2:2, 2:2.5, 2:3, 2:3.5, 2:4, 2:4.5, or 2:5. In this invention, the preferred mass concentration of the aqueous solution of ethylene glycol diglycidyl ether is 1% to 5%, and in specific embodiments, it can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%. This invention does not have a specific limitation on the dropping rate of the aqueous solution of ethylene glycol diglycidyl ether; it can be added dropwise at a uniform rate.

[0154] In this invention, the epoxidation modification temperature is preferably 95-100℃, and in specific embodiments it can be 95℃, 96℃, 97℃, 98℃, 99℃ or 100℃; the epoxidation modification time is preferably 2-6h, and in specific embodiments it can be 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h or 6h.

[0155] After the epoxidation modification is completed, the present invention preferably further includes: filtering the reaction system obtained by the epoxidation modification, and sequentially washing the obtained solid with water, washing with ethanol, extracting with acetone, and drying to obtain epoxidized chitosan. In the present invention, the drying temperature is preferably 50-60°C, more preferably 55°C; the present invention does not have a special limitation on the drying time, drying to constant weight is sufficient.

[0156] In this invention, the preferred method for preparing ethylene glycol diglycidyl ether includes the following steps: mixing ethylene glycol, a catalyst, and epichlorohydrin, performing a ring-opening addition reaction, and then performing a ring-closing reaction under alkaline conditions to obtain ethylene glycol diglycidyl ether. The reaction route is as follows:

[0157]

[0158] In this invention, the ethylene glycol is preferably dried before use. Specifically, ethylene glycol is added to a reaction vessel, heated to remove air and moisture, dried, and then cooled to obtain dried ethylene glycol. In this invention, the heating temperature is preferably 90–100°C, and in specific embodiments, it can be 90°C, 92°C, 94°C, 95°C, 96°C, 98°C, or 100°C. In this invention, the drying time is preferably 30–35 minutes, and in specific embodiments, it can be 30 minutes, 31 minutes, 32 minutes, 33 minutes, 34 minutes, or 35 minutes. In this invention, the cooling temperature is preferably 50–85°C, and in specific embodiments, it can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, or 85°C.

[0159] In this invention, the catalyst preferably comprises a boron trifluoride diethyl ether complex. In this invention, the catalyst preferably accounts for 0.4% to 0.6% of the mass of ethylene glycol, and in specific embodiments, it can be 0.4%, 0.45%, 0.5%, 0.55%, or 0.6%.

[0160] In this invention, the mixing preferably includes adding ethylene glycol and a catalyst, followed by the dropwise addition of epichlorohydrin. In this invention, the mixing temperature is preferably 50–85°C, and in specific embodiments, it can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, or 85°C. This invention does not have a particular limitation on the dropping rate of epichlorohydrin, as long as the temperature of the reaction system is maintained at 50–85°C.

[0161] In this invention, the molar ratio of epichlorohydrin to ethylene glycol is 2.2 to 2.5:1, and in specific embodiments it can be 2.2:1, 2.3:1, 2.4:1 or 2.5:1.

[0162] In this invention, the temperature of the ring-opening addition reaction is preferably 50–85°C, and in specific embodiments it can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, or 85°C; the time of the ring-opening addition reaction is preferably 40–60 min, and in specific embodiments it can be 40 min, 45 min, 50 min, 55 min, or 60 min; the time of the ring-opening addition reaction begins to be timed from the time the epichlorohydrin is completely added.

[0163] In this invention, the alkaline conditions are preferably provided by an alkali metal hydroxide, which preferably includes NaOH and / or KOH; the alkali metal hydroxide is preferably used in the form of an aqueous solution; the mass concentration of the aqueous solution is preferably 40-60%, and in specific embodiments it can be 40%, 45%, 50%, 55%, or 60%; the aqueous solution is preferably added dropwise; in this invention, the system after the ring-opening addition reaction is preferably cooled to 35-45°C (in specific embodiments it can be 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, 43°C, 44°C, or 45°C) before the aqueous solution is added dropwise. In this invention, the molar ratio of epichlorohydrin to alkali metal hydroxide is preferably 1.5-2:1, and in specific embodiments it can be 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, or 2:1.

[0164] In this invention, the temperature of the closed-loop reaction is preferably 35-45°C, and in specific embodiments it can be 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, 43°C, 44°C or 45°C; the time of the closed-loop reaction is preferably 1-3 hours, and in specific embodiments it can be 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours; the time of the closed-loop reaction begins to be counted from the time the alkali metal hydroxide is completely added.

[0165] After completing the closed-loop reaction, the present invention preferably further includes: hot filtration of the reaction system obtained from the closed-loop reaction, allowing the filtrate to stand and separate phases, and vacuum distillation of the upper crude product to obtain ethylene glycol diglycidyl ether. In the present invention, the purpose of hot filtration is to remove the alkali metal chloride salts generated in the reaction. In the present invention, the purpose of vacuum distillation is to remove residual water and reaction raw materials.

[0166] The preparation method of molybdenum dioxide nanoparticles is described in detail below.

[0167] In this invention, the preferred method for preparing the molybdenum dioxide nanoparticles includes the following steps: mixing an aqueous glucose solution and an aqueous sodium molybdate solution, adjusting the pH value to 1-4, and carrying out a hydrothermal reaction to obtain molybdenum dioxide nanoparticles.

[0168] In this invention, the concentration of the glucose aqueous solution is preferably 0.5–1 mol / L, and in specific embodiments it can be 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, or 1 mol / L. In this invention, the concentration of the sodium molybdate aqueous solution is preferably 0.5–1 mol / L, and in specific embodiments it can be 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, or 1 mol / L. In this invention, the volume ratio of the glucose aqueous solution to the sodium molybdate aqueous solution is preferably 2–4:1, and in specific embodiments it can be 2:1, 2.5:1, 3:1, 3.5:1, or 4:1.

[0169] In this invention, the mixing temperature is preferably 25-30°C; the mixing time is preferably 10-15 min, and in specific embodiments it can be 10 min, 11 min, 12 min, 13 min or 14 min, 15 min.

[0170] In this invention, the acid used to adjust the pH value to 1-4 preferably includes an HCl solution, and the concentration of the HCl solution is preferably 2-3 mol / L, more preferably 2.5 mol / L; in specific embodiments, the pH value can be 1, 1.5, 2, 2.5, 3, 3.5 or 4.

[0171] In this invention, the temperature of the hydrothermal reaction is preferably 180–220°C, and in specific embodiments, it can be 180°C, 190°C, 200°C, 210°C, or 220°C; the time of the hydrothermal reaction is preferably 18–25 h, and in specific embodiments, it can be 18 h, 19 h, 20 h, 21 h, 22 h, 23 h, 24 h, or 25 h; the hydrothermal reaction preferably includes: placing the acidic mixture after adjusting the pH value to 1–4 into a reaction vessel, and placing the reaction vessel into a homogeneous hydrothermal reactor for hydrothermal reaction; the reaction vessel preferably includes a high-pressure hydrothermal reactor with a polytetrafluoroethylene liner, and the volume filling ratio of the reaction vessel is preferably 40–70%, more preferably 50–60%.

[0172] After completing the hydrothermal reaction, the present invention preferably further includes: cooling the reaction system obtained from the hydrothermal reaction to room temperature, centrifuging, and sequentially washing the obtained solid with water, washing with anhydrous ethanol, and drying to obtain molybdenum dioxide nanoparticles (monoclinic phase). In the present invention, the number of water washings is preferably 2-3 times. In the present invention, the number of anhydrous ethanol washings is preferably 2-3 times. In the present invention, the drying temperature is preferably...

[0173] Drying involves placing the centrifuged and washed powder material at 60–80°C, which in specific embodiments can be 60°C, 65°C, 70°C, 75°C, or 80°C; the drying time is preferably 10–15 hours, which in specific embodiments can be 10 hours, 11 hours, 12 hours, 13 hours, 4 hours, or 15 hours; the drying is preferably carried out in a vacuum drying oven.

[0174] This invention provides a method for preparing the tissue-like natural collagen composite absorbable suture described in the above technical solution, comprising the following steps: mixing medical-grade tissue-like natural collagen, epoxidized chitosan, molybdenum dioxide nanoparticles, sodium alginate and water to obtain a spinning solution; spinning the spinning solution to obtain the tissue-like natural collagen composite absorbable suture.

[0175] In this invention, the mass ratio of the tissue-like natural collagen, epoxidized chitosan, and sodium alginate is the same as the mass ratio of the three components in the tissue-like natural collagen composite absorbable suture, and will not be repeated here.

[0176] In this invention, the concentration of medical grade tissue natural collagen in the spinning solution is preferably 12-25 wt%, and in specific embodiments it can be 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, or 25 wt%.

[0177] In this invention, the mixing preferably includes ultrasonic mixing. This invention does not have any special limitations on the mixing conditions, as long as the molybdenum dioxide nanoparticles are uniformly dispersed and the other raw materials are uniformly mixed.

[0178] After the spinning process is completed, the present invention preferably further includes: straightening the filaments obtained by spinning and then solidifying them to obtain a tissue-like natural collagen composite absorbable suture.

[0179] In this invention, the preferred spinning process conditions include: a coagulation bath of saturated sodium sulfate; a pressure of 0.05–0.2 MPa, which in specific embodiments can be 0.05 MPa, 0.1 MPa, 0.15 MPa, or 0.2 MPa; a spinning solution temperature of room temperature; a coagulation temperature of 25–35°C, which in specific embodiments can be 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C, or 35°C; and a winding speed of 8–15 m / min, which in specific embodiments can be 8 m / min, 9 m / min, 10 m / min, 11 m / min, 12 m / min, 13 m / min, 14 m / min, or 15 m / min; and the spinning is preferably carried out in a wet spinning machine.

[0180] This invention uses medical-grade tissue-like natural collagen, epoxy-modified chitosan, molybdenum dioxide nanoparticles, and sodium alginate as raw materials. These materials are blended to form a spinning solution, which is then spun to prepare a novel medical-grade, antibacterial, and scar-reducing tissue-like natural collagen composite absorbable suture. The prepared tissue-like natural collagen composite absorbable suture retains the advantages of medical-grade tissue-like natural collagen raw materials and, due to the participation of chitosan, can resist corrosion from bile, urine, and pancreatic juice. Compared to existing natural absorbable sutures, which suffer from drawbacks such as low processing cost, insufficient antigenicity, poor structural stability, short degradation cycle, and poor fixation, this novel material has significant advantages, broad prospects, and is of great importance.

[0181] This invention also provides the application of the tissue-like natural collagen composite absorbable suture described in the above-mentioned technical solutions, or the tissue-like natural collagen composite absorbable suture prepared by the above-mentioned technical solutions, in tissue engineering, regenerative medicine materials, or implantable medical devices. In the tissue-like natural collagen composite absorbable suture provided by this invention, the medical-grade tissue-like natural collagen possesses good biocompatibility, suitable biodegradability, good mechanical properties, and excellent thermal and structural stability. It has low antigenicity and is easy to preserve. Furthermore, it can quickly and effectively stop bleeding, promote wound healing and repair, making it an ideal material for biomedical materials. It can fundamentally solve the problems of rapid biodegradation and insufficient mechanical strength existing in collagen molecular-level materials or gelatin materials. This invention, by using tissue-like natural collagen, also realizes the reuse of natural biological tissues. This invention, by adding epoxidized modified chitosan to supplement and modify the material, inhibits the growth and reproduction of various bacteria and fungi, promotes skin regeneration, and accelerates wound healing after suturing. Molybdenum dioxide, as a metallic semiconductor, possesses excellent electrical conductivity. This invention, by adding molybdenum dioxide nanoparticles, not only improves the conductivity of tissue-like natural collagen composite absorbable sutures, further enhancing their wear resistance and anti-slip properties, but also, due to the photothermal effect of molybdenum dioxide, brings about a significant scar-reducing effect. The sodium alginate added in this invention is a linear polysaccharide with excellent biocompatibility, biodegradability, non-toxicity, and low raw material cost. Chitosan and its derivatives have broad-spectrum antibacterial effects, inhibiting the reproduction and growth of various bacteria and fungi, and possess the advantages of being non-toxic and having strong antibacterial properties. Wound dressings with added chitosan can prevent bacterial penetration, promote skin regeneration, and accelerate wound healing, in addition to their good biocompatibility, strength, flexibility, and bioabsorbability. The tissue-like natural collagen composite absorbable suture provided by this invention fully combines the advantageous functions of the components used, retains the excellent mechanical properties and biodegradability of natural collagen composite materials, has low antigenicity and excellent antibacterial properties, and also combines the photothermal effect of molybdenum dioxide, which has a significant scar-reducing effect; it also has good fixation, and can resist the corrosion of bile, urine and pancreatic juice, and promote cell growth.

[0182] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, of the tissue-like natural collagen composite absorbable suture, its preparation method, and its application, should not be construed as limiting the scope of protection of the present invention.

[0183] In the following examples, the ratio of mass parts to volume parts is kg:L, and the animal skin used is pigskin.

[0184] Example 1

[0185] Preparation of medical-grade tissue-derived natural collagen:

[0186] A) Animal skin pretreatment: Animal skin is placed in a rotating drum for repeated washing to remove dirt. After washing, it is soaked in water for 2 hours and then mechanically processed to remove as much subcutaneous fat, surface muscle, blood vessels and fascia as possible. Then it is cut into small pieces of 5.0mm×5.0mm, thoroughly washed with physiological saline at room temperature and soaked for 15 hours to obtain pretreated animal skin.

[0187] B) Degreasing treatment of animal skin: Take 10 parts by weight of the pretreated animal skin above and put it into a drum. Add 0.2 parts by weight of alkyl polyglycoside and water (the solid-liquid ratio of pretreated animal skin to water is 1kg:2L). Degrease at 35℃ and drum speed of 8r / min for 3h. After degreasing, rinse off excess chemical reagents and oils with warm water at 35℃ to obtain degreased animal skin.

[0188] C) Dehairing treatment of animal skin: Place the above-mentioned degreased animal skin in water (the solid-liquid ratio of pretreated animal skin to water is 1kg:2L), add 5 parts by weight of fatty alcohol polyoxyethylene ether and 4 parts by weight of ferrous sulfate to the water, rotate at 35℃ and a drum speed of 8r / min for 2h, add 0.2 parts by weight of triethanolamine, continue to rotate for 20min, add 0.4 parts by weight of sodium hydroxide, rotate for 20min, add 0.6 parts by weight of hydrogen peroxide to rinse for 4h, add 0.5% sodium hydroxide solution to soak for 5h, and then rinse repeatedly with water to obtain dehaired animal skin;

[0189] D) De-swelling treatment of animal hides: The above-mentioned dehaired animal hides were placed in a drum, water was added (the solid-liquid ratio of pretreated animal hides to water was 1 kg: 1 L), the temperature was controlled at 28℃, and 0.1% sodium bisulfite by weight of the pretreated animal hides was added. The drum was rotated at 35℃ and a speed of 8 r / min for 60 min, with the final pH value controlled at 8. After the rotation, 10 parts by volume of water and 4 parts by volume of formic acid were added to the same bath, and the pH value was controlled at 4. Then, 0.2% acidic lipase by weight of the pretreated animal hides was added, and the drum was rotated for 20 min. Then, 0.3% acidic protease by weight of the pretreated animal hides was added, and the reaction was carried out at a constant temperature of 40℃ for 5 h. Finally, the hides were rinsed repeatedly with ultrapure water to obtain de-swelled animal hides.

[0190] E) Acid swelling treatment of animal skin: Add water to the above-mentioned de-swelled animal skin (the solid-liquid ratio of pretreated animal skin to water is 1 kg: 2 L), adjust the pH value to 3.0 with a mixed acid solution of 0.05-0.08 wt% formic acid solution and 0.08-0.12 wt% sulfuric acid solution (volume ratio = 1:2), rotate at 35℃ and drum speed of 8 r / min for 1 h, let stand for 8 h, and rinse repeatedly with water to obtain acid-swollen animal skin;

[0191] Preparation of F) Type F tissue-based natural collagen: The above-mentioned acid-swollen animal skin was placed in a ball mill jar along with grinding balls, with a ball-to-material ratio of 1:1.5. The mixture was ball-milled for 2 hours at 400 r / min. After milling, the slurry was centrifuged at 15000 r / min for 15 minutes. The supernatant was removed, and the slurry was collected. The pH of the slurry was adjusted to 7.0 using a 0.1 mol / L sodium hydroxide aqueous solution, and centrifuged again at 15000 r / min for 15 minutes. The precipitate was collected and washed five times with ultrapure water. The precipitate was then freeze-dried and sterilized using γ-rays generated at a dose of 15 kGy / h 60Co to obtain medical-grade type F tissue-based natural collagen. The grinding media used in the ball mill consisted of large balls with a diameter of 12–13 mm and small balls with a diameter of 9–10 mm, with a large-to-small ball ratio of 1:2.

[0192] Preparation of chitosan modified by ethylene glycol diglycidyl ether epoxidation:

[0193] A) Preparation of ethylene glycol diglycidyl ether: Ethylene glycol was added to the reaction flask and heated to 90°C in a constant temperature water bath. Air and moisture in the reaction flask were removed and heated for 30 min. The temperature was then lowered to 65°C, and 0.4% (w / w) boron trifluoride diethyl ether complex of ethylene glycol was added. Epichlorohydrin (molar ratio of epichlorohydrin to ethylene glycol was 2.2:1) was added dropwise, and the dropping rate was controlled to keep the temperature constant. After the addition was completed, the reaction was continued for 40 min.

[0194] The temperature was lowered to 40℃, and after the temperature was constant, a 40% NaOH aqueous solution (the molar ratio of epichlorohydrin to NaOH was 2:1) was added dropwise. After the addition was complete, the reaction continued for 2 hours. After the reaction was complete, the sodium chloride generated in the reaction was removed by vacuum filtration. The filtrate was placed in a separatory funnel and allowed to stand for phase separation. The lower layer of saturated sodium chloride aqueous solution was filtered off, and the upper crude product was distilled under reduced pressure to remove residual water and reactants, yielding ethylene glycol diglycidyl ether.

[0195] B) Epoxidized chitosan: Take 2g of chitosan powder and suspend it in 20mL of distilled water. Heat the mixture to 95℃ and add 3g of 2% ethylene glycol diglycidyl ether aqueous solution. Then continue stirring and reacting for 3h. Filter out the solid, wash it with water, ethanol, and acetone, and then dry it at 50℃ to constant weight to obtain epoxidized chitosan.

[0196] Preparation of monoclinic molybdenum dioxide nanoparticles:

[0197] C6H at a concentration of 0.5 mol / L 12Aqueous solutions of O6·H2O and 0.5 mol / L Na2MoO4·2H2O were mixed at a volume ratio of 2:1 and stirred at 30℃ for 10 min. The pH of the mixed solution was adjusted to 2 using 2 mol / L HCl solution, and the mixture was poured into a polytetrafluoroethylene-lined high-pressure hydrothermal reactor with a volume filling ratio of 40%. The reactor was then sealed and placed in a homogeneous hydrothermal reactor, where it was reacted at 180℃ for 18 h. After the reaction was completed, the mixture was cooled to room temperature, and the final reactants were centrifuged and washed three times each with deionized water and anhydrous ethanol. The resulting product was then dried in a vacuum drying oven at 60℃ for 12 h to obtain monoclinic molybdenum dioxide nanoparticles.

[0198] Preparation of tissue-like natural collagen composite absorbable sutures:

[0199] Medical-grade tissue-derived natural collagen, epoxidized chitosan, monoclinic molybdenum dioxide nanoparticles, and sodium alginate were mixed in distilled water, stirred evenly, and ultrasonically dispersed to obtain a spinning solution. The spinning solution was poured into a wet spinning machine and spun into long filaments, which were then straightened and solidified to obtain a circular cross-section natural collagen composite absorbable suture. The mass ratio of medical-grade tissue-derived natural collagen, epoxidized chitosan, monoclinic molybdenum dioxide nanoparticles, and sodium alginate was 10:1:0.1:1. The concentration of medical-grade tissue-derived natural collagen in the spinning solution was 15wt%. The spinning process conditions were as follows: coagulation bath: saturated sodium sulfate; pressure: 0.1MPa; spinning solution temperature: room temperature; coagulation temperature: 25℃; winding speed: 10m / min.

[0200] Example 2

[0201] Preparation of medical-grade tissue-derived natural collagen:

[0202] A) Animal skin pretreatment: Animal skin is placed in a rotating drum for repeated washing to remove dirt. After washing, it is soaked in water for 2 hours and then mechanically processed to remove as much subcutaneous fat, surface muscle, blood vessels and fascia as possible. Then it is cut into small pieces of 5.0mm×5.0mm, thoroughly washed with physiological saline at room temperature and soaked for 15 hours to obtain pretreated animal skin.

[0203] B) Degreasing treatment of animal skin: Take 10 parts by weight of the pretreated animal skin above and put it into a drum. Add 0.15 parts by weight of alkyl polyglycoside and water (the solid-liquid ratio of pretreated animal skin to water is 1 kg: 2 L). Degrease for 2.5 h at 30 °C and drum speed of 10 r / min. After degreasing, rinse off excess chemical reagents and grease with warm water at 35 °C to obtain degreased animal skin.

[0204] C) Dehairing treatment of animal hides: The above-mentioned degreased animal hides were placed in water (the solid-liquid ratio of the pretreated animal hides to water was 1 kg: 1.5 L), 5 parts by weight of fatty alcohol polyoxyethylene ether and 4 parts by weight of ferrous sulfate were added to the water, and the mixture was rotated at 30°C and a drum speed of 10 r / min for 2 hours. 0.3 parts by weight of triethanolamine were added, and the mixture was rotated for another 20 minutes. 0.4 parts by weight of sodium hydroxide were added, and the mixture was rotated for another 20 minutes. 0.6 parts by weight of hydrogen peroxide were added and the mixture was rinsed for 3 hours. The mixture was then soaked in a 0.5% sodium hydroxide solution for 5 hours, and then rinsed repeatedly with water to obtain the dehaired animal hides.

[0205] D) De-swelling treatment of animal hides: The above-mentioned dehaired animal hides were placed in a drum, water was added (the solid-liquid ratio of pretreated animal hides to water was 1 kg: 1 L), the temperature was controlled at 28℃, and 0.1% sodium bisulfite by weight of the pretreated animal hides was added. The drum was rotated at 30℃ and 10 r / min for 50 min, and the final pH value was controlled at 8. After the rotation, 10 parts by volume of water and 4 parts by volume of formic acid were added to the same bath, and the pH value was controlled at 4.5. Then, 0.25% acidic lipase by weight of the pretreated animal hides was added, and the drum was rotated for 20 min. Then, 0.25% acidic protease by weight of the pretreated animal hides was added, and the reaction was carried out at a constant temperature of 40℃ for 5 h. Finally, the hides were rinsed repeatedly with ultrapure water to obtain de-swelled animal hides.

[0206] E) Acid swelling treatment of animal skin: Add water to the above-mentioned de-swelled animal skin (the solid-liquid ratio of pretreated animal skin to water is 1 kg: 2 L), adjust the pH value to 3.0 with a mixed acid solution of 0.05-0.08 wt% formic acid solution and 0.08-0.12 wt% sulfuric acid solution (volume ratio = 1:2), rotate at 30℃ and drum speed of 10 r / min for 2 hours, let stand for 8 hours, and rinse repeatedly with water to obtain acid-swollen animal skin;

[0207] Preparation of F) Type F tissue-derived natural collagen: The above-mentioned acid-swollen animal skin and grinding media were placed in a ball mill jar with a media-to-material ratio of 1:1.5. The mixture was ball-milled for 2 hours at 400 r / min. After milling, the slurry was centrifuged at 18000 r / min for 15 minutes. The supernatant was removed, and the slurry was collected. The pH of the slurry was adjusted to 7.0 using a 0.1 mol / L sodium hydroxide aqueous solution, and centrifuged at 18000 r / min for 15 minutes. The precipitate was collected, washed five times with ultrapure water, freeze-dried, and sterilized using γ-rays generated by 20 kGy / h 60Co to obtain medical-grade type F tissue-derived natural collagen. The grinding media used in the ball milling consisted of large balls with a diameter of 12–13 mm and small balls with a diameter of 9–10 mm, with a large ball to small ball ratio of 1:2.

[0208] Preparation of chitosan modified by ethylene glycol diglycidyl ether epoxidation:

[0209] A) Preparation of ethylene glycol diglycidyl ether: Ethylene glycol was added to the reaction flask and heated to 90°C in a constant temperature water bath to remove air and moisture from the reaction flask. The mixture was heated for 35 min and then cooled to 85°C. A boron trifluoride diethyl ether complex with a mass fraction of 0.6% by weight of ethylene glycol was added, and epichlorohydrin (molar ratio of epichlorohydrin to ethylene glycol was 2.2:1) was added dropwise. The dropping rate was controlled to keep the temperature constant. After the addition was completed, the reaction was continued for 40 min.

[0210] The temperature was lowered to 40℃, and after the temperature was constant, a 40% NaOH aqueous solution (the molar ratio of epichlorohydrin to NaOH was 2:1) was added dropwise. After the addition was complete, the reaction continued for 3 hours. After the reaction was complete, the sodium chloride generated in the reaction was removed by vacuum filtration. The filtrate was placed in a separatory funnel and allowed to stand for phase separation. The lower layer of saturated sodium chloride aqueous solution was filtered off, and the upper crude product was distilled under reduced pressure to remove residual water and reactants, yielding ethylene glycol diglycidyl ether.

[0211] B) Epoxidized chitosan: Take 2g of chitosan powder and suspend it in 25mL of distilled water. Heat the mixture to 95℃ and add 2.5g of 5% ethylene glycol diglycidyl ether aqueous solution. Then continue stirring and reacting for 5h. Filter out the solid, wash it with water, ethanol, and acetone, and then dry it at 60℃ to constant weight to obtain epoxidized chitosan.

[0212] Preparation of monoclinic molybdenum dioxide nanoparticles:

[0213] A concentration of 1 mol / L of C6H 12 Aqueous solutions of O6·H2O and 1 mol / L Na2MoO4·2H2O were mixed at a volume ratio of 4:1 and stirred at 30℃ for 15 min. The pH of the mixed solution was adjusted to 3 using 3 mol / L HCl solution, and the mixture was poured into a polytetrafluoroethylene-lined high-pressure hydrothermal reactor with a volume filling ratio of 50%. The reactor was then sealed and placed in a homogeneous hydrothermal reactor, where it was reacted at 200℃ for 20 h. After the reaction was completed, the mixture was cooled to room temperature, and the final reactants were centrifuged and washed three times each with deionized water and anhydrous ethanol. The mixture was then dried in an 80℃ vacuum drying oven for 10 h to obtain monoclinic molybdenum dioxide nanoparticles.

[0214] Preparation of tissue-like natural collagen composite absorbable sutures:

[0215] Medical-grade tissue-derived natural collagen, epoxidized chitosan, monoclinic molybdenum dioxide nanoparticles, and sodium alginate were mixed in distilled water, stirred evenly, and ultrasonically dispersed to obtain a spinning solution. The spinning solution was poured into a wet spinning machine and spun into long filaments, which were then straightened and solidified to obtain a circular cross-section natural collagen composite absorbable suture. The mass ratio of medical-grade tissue-derived natural collagen, epoxidized chitosan, monoclinic molybdenum dioxide nanoparticles, and sodium alginate was 10:0.5:0.05:0.5. The concentration of medical-grade tissue-derived natural collagen in the spinning solution was 18wt%. The spinning process conditions were as follows: coagulation bath: saturated sodium sulfate; pressure: 0.2MPa; spinning solution temperature: room temperature; coagulation temperature: 30℃; winding speed: 12m / min.

[0216] Example 3

[0217] Preparation of medical-grade tissue-derived natural collagen:

[0218] A) Animal skin pretreatment: Place the animal skin in a rotating drum for repeated washing to remove dirt. After washing, soak it in water for 1 hour, and then mechanically remove the meat to remove as much subcutaneous fat, surface muscle, blood vessels and fascia as possible. Then cut it into 10.0mm×10.0mm pieces, wash thoroughly with physiological saline at room temperature and soak for 18 hours to obtain pretreated animal skin.

[0219] B) Degreasing treatment of animal skin: Take 10 parts by weight of the pretreated animal skin above and put it into a drum. Add 0.4 parts by weight of alkyl polyglycoside and water (the solid-liquid ratio of pretreated animal skin to water is 1kg:3L). Degrease at 30℃ and drum speed of 10r / min for 4 hours. After degreasing, rinse off excess chemical reagents and grease with warm water at 30℃ to obtain degreased animal skin.

[0220] C) Dehairing treatment of animal skin: Place the above-mentioned degreased animal skin in water (the solid-liquid ratio of pretreated animal skin to water is 1kg:2L), add 3 parts by weight of fatty alcohol polyoxyethylene ether and 6 parts by weight of ferrous sulfate to the water, rotate at 30℃ and a drum speed of 10r / min for 2h, add 0.45 parts by weight of triethanolamine, continue to rotate for 20min, add 0.8 parts by weight of sodium hydroxide, rotate for 10min, add 0.8 parts by weight of hydrogen peroxide to rinse for 3h, add 0.5% sodium hydroxide solution to soak for 5h, and then rinse repeatedly with water to obtain dehaired animal skin;

[0221] D) De-swelling treatment of animal hides: The above-mentioned dehaired animal hides were placed in a drum, water was added (the solid-liquid ratio of pretreated animal hides to water was 1 kg: 8 L), the temperature was controlled at 28℃, and 0.2% sodium bisulfite by weight of the pretreated animal hides was added. The drum was rotated at 30℃ and a speed of 10 r / min for 50 min, and the final pH value was controlled at 8. After the rotation, 10 parts by volume of water and 3 parts by volume of formic acid were added to the same bath to control the pH value at 4.5. Then, 0.15% acidic lipase by weight of the pretreated animal hides was added, and the drum was rotated for 20 min. Then, 0.15% acidic protease by weight of the pretreated animal hides was added, and the reaction was carried out at a constant temperature of 40℃ for 5 h. Finally, the hides were rinsed repeatedly with ultrapure water to obtain de-swelled animal hides.

[0222] E) Acid swelling treatment of animal skin: Add water to the above-mentioned de-swelled animal skin (the solid-liquid ratio of pretreated animal skin to water is 1 kg: 2 L), adjust the pH value to 3.0 with a mixed acid solution of 0.05-0.08 wt% formic acid solution and 0.08-0.12 wt% sulfuric acid solution (volume ratio = 1:2), rotate at 30℃ and drum speed of 10 r / min for 2 hours, let stand for 8 hours, and rinse repeatedly with water to obtain acid-swollen animal skin;

[0223] Preparation of F) Type F tissue-based natural collagen: The above-mentioned acid-swollen animal skin was placed in a ball mill jar along with grinding balls, with a ball-to-material ratio of 1:1.5. The mixture was ball-milled for 3 hours at 600 r / min. After milling, the slurry was centrifuged at 18000 r / min for 15 minutes. The supernatant was removed, and the slurry was collected. The pH of the slurry was adjusted to 7.0 using a 0.1 mol / L sodium hydroxide aqueous solution, and centrifuged at 18000 r / min for 15 minutes. The precipitate was collected, washed five times with ultrapure water, freeze-dried, and sterilized using γ-rays generated at a dose of 25 kGy / h 60Co to obtain medical-grade type F tissue-based natural collagen. The grinding media used in the ball mill consisted of large balls with a diameter of 12–13 mm and small balls with a diameter of 9–10 mm, with a large-to-small ball ratio of 1:2.

[0224] Preparation of chitosan modified by ethylene glycol diglycidyl ether epoxidation:

[0225] A) Preparation of ethylene glycol diglycidyl ether: Ethylene glycol was added to the reaction flask and heated to 90°C in a constant temperature water bath. Air and moisture in the reaction flask were removed and heated for 30 min. The temperature was then lowered to 65°C, and 0.5% (w / w) boron trifluoride diethyl ether complex of ethylene glycol was added. Epichlorohydrin (molar ratio of epichlorohydrin to ethylene glycol was 2.2:1) was added dropwise, and the dropping rate was controlled to keep the temperature constant. After the addition was completed, the reaction was continued for 40 min.

[0226] The temperature was lowered to 40℃, and after the temperature was constant, a 40% NaOH aqueous solution (the molar ratio of epichlorohydrin to NaOH was 2:1) was added dropwise. After the addition was complete, the reaction continued for 2 hours. After the reaction was complete, the sodium chloride generated in the reaction was removed by vacuum filtration. The filtrate was placed in a separatory funnel and allowed to stand for phase separation. The lower layer of saturated sodium chloride aqueous solution was filtered off, and the upper crude product was distilled under reduced pressure to remove residual water and reactants, yielding ethylene glycol diglycidyl ether.

[0227] B) Epoxidized chitosan: Take 2g of chitosan powder and suspend it in 25mL of distilled water. Heat the mixture to 95℃ and add 3g of 5% ethylene glycol diglycidyl ether aqueous solution. Then continue stirring and reacting for 4h. Filter out the solid, wash it with water, ethanol, and acetone, and then dry it at 60℃ to constant weight to obtain epoxidized chitosan.

[0228] Preparation of monoclinic molybdenum dioxide nanoparticles:

[0229] A concentration of 1 mol / L of C6H 12 Aqueous solutions of O6·H2O and 1 mol / L Na2MoO4·2H2O were mixed at a volume ratio of 2:1 and stirred at 30℃ for 15 min. The pH of the mixed solution was adjusted to 2 using 3 mol / L HCl solution, and the mixture was poured into a polytetrafluoroethylene-lined high-pressure hydrothermal reactor with a volume filling ratio of 40%. The reactor was then sealed and placed in a homogeneous hydrothermal reactor, where it was reacted at 220℃ for 18 h. After the reaction was completed, the mixture was cooled to room temperature, and the final reactants were centrifuged and washed three times each with deionized water and anhydrous ethanol. The mixture was then dried in an 80℃ vacuum drying oven for 10 h to obtain monoclinic molybdenum dioxide nanoparticles.

[0230] Preparation of tissue-like natural collagen composite absorbable sutures:

[0231] Medical-grade tissue-derived natural collagen, epoxidized chitosan, monoclinic molybdenum dioxide nanoparticles, and sodium alginate were mixed in distilled water, stirred evenly, and ultrasonically dispersed to obtain a spinning solution. The spinning solution was poured into a wet spinning machine and spun into long filaments, which were then straightened and solidified to obtain a circular cross-section natural collagen composite absorbable suture. The mass ratio of medical-grade tissue-derived natural collagen, epoxidized chitosan, monoclinic molybdenum dioxide nanoparticles, and sodium alginate was 10:0.25:0.05:0.25. The concentration of medical-grade tissue-derived natural collagen in the spinning solution was 25 wt%. The spinning process conditions were as follows: coagulation bath: saturated sodium sulfate; pressure: 0.2 MPa; spinning solution temperature: room temperature; coagulation temperature: 30℃; winding speed: 15 m / min.

[0232] Figure 1This is a photograph of the tissue-like natural collagen composite absorbable suture prepared in Example 1. Figure 2 This is a photograph of the tissue-like natural collagen composite absorbable suture prepared in Example 2. Figure 3 This is a photograph of the tissue-like natural collagen composite absorbable suture prepared in Example 3. Figures 1-3 It is known that the tissue-like natural collagen composite absorbable suture prepared by this invention is a multi-strand suture.

[0233] Example 4

[0234] A) Animal skin pretreatment: Animal skin is placed in a rotating drum for repeated washing to remove dirt. After washing, it is soaked in water for 90 minutes and then mechanically processed to remove as much subcutaneous fat, surface muscle, blood vessels and fascia as possible. Then it is cut into small pieces of 8.0mm×8.0mm, thoroughly washed with physiological saline at room temperature and soaked for 13 hours to obtain pretreated animal skin.

[0235] B) Degreasing treatment of animal skin: Take 10 parts by weight of the pretreated animal skin above and put it into a drum. Add 0.3 parts by weight of alkyl polyglycoside and 20 parts by volume of deionized water. Degrease at 35°C for 3 hours. After degreasing, wash repeatedly with 38°C warm water 4 times to obtain degreased animal skin.

[0236] C) Dehairing treatment of animal skin: Place the above-mentioned degreased animal skin in an equal mass of water, add 5 parts by weight of fatty alcohol polyoxyethylene ether and 4 parts by weight of ferrous sulfate to the water, rotate in a drum for 2 hours, add 0.2 parts by weight of triethanolamine, continue rotating for 15 minutes, add 0.4 parts by weight of sodium hydroxide, rotate for 20 minutes, add 0.7 parts by weight of hydrogen peroxide, rotate for 3.5 hours, after which soak in a 0.5% sodium hydroxide solution for 5 hours, and then rinse repeatedly with ultrapure water 4 times to obtain the dehaired animal skin;

[0237] D) Treatment of animal skin to remove swelling: Place the above-mentioned dehaired animal skin into a drum, add 9 parts by volume of ultrapure water, control the temperature at 30℃, and add sodium bisulfite at 0.12% of the skin weight. Rotate for 55 minutes, and control the pH value at the end point at about 8.3. After the rotation, add 10 parts by volume of deionized water and 3.5 parts by volume of formic acid to the same bath, control the pH value at 4.2, then add 0.2% acidic lipase, rotate for 20 minutes, then add 0.2% acidic protease, and react at a constant temperature of 40℃ for 3 hours. Finally, rinse repeatedly with ultrapure water 4 times to obtain the de-swelled animal skin.

[0238] E) Treatment of animal skin with acid swelling: Add 15 volumes of ultrapure water to the above-mentioned de-swelled animal skin, adjust the pH to 2.9 with a mixed acid solution of 0.05-0.08 wt% formic acid solution and 0.08-0.12 wt% sulfuric acid solution (volume ratio = 1:2), stir for 0.8 h, let stand for 7 h, and then rinse repeatedly with ultrapure water 4 times to obtain acid-swollen animal skin;

[0239] Preparation of F) Type F tissue-derived natural collagen: The above-mentioned acid-swollen animal skin and grinding media were placed in a ball mill jar with a media-to-material ratio of 1:3. The mixture was ball-milled for 120 minutes at 400 r / min. After milling, the slurry was centrifuged at 16000 r / min for 13 minutes. The supernatant was removed, and the slurry was collected. The pH of the slurry was adjusted to 7.2 using sodium carbonate, and centrifuged again at 16000 r / min for 13 minutes. The precipitate was collected and washed four times with ultrapure water. Finally, the precipitate was freeze-dried and sterilized using γ-rays generated at a dose of 18 kGy / h 60Co. The mixture was then shaped and packaged to obtain medical-grade type F tissue-derived natural collagen. The grinding media used in the ball mill consisted of large balls with a diameter of 12–13 mm and small balls with a diameter of 9–10 mm, with a large ball to small ball ratio of 1:2. In this embodiment, the drum speed was 10 r / min.

[0240] Comparative Example 1

[0241] Antigen-free collagen aggregates prepared in Example 2 of Chinese Patent CN104107456A.

[0242] Comparative Example 1 used acetone and supercritical fluid for degreasing. Acetone has a certain degree of toxicity, and the industrialization of supercritical fluid equipment is relatively complex. To achieve the same degreasing effect, this invention uses alkyl polyglycosides with better biocompatibility, and the equipment is a conventional leather equipment drum, making it more suitable for industrial applications. The preparation method provided by this invention adds a hair removal step compared to Comparative Example 1. This step can further remove non-collagen components in the leather, such as impurities and interfibrous matrix, while removing hair, further loosening the collagen fibers in the leather, facilitating subsequent extraction of natural collagen, and improving the extraction rate of natural collagen. Comparative Example 1 used a homogenizer process, which inevitably resulted in a large number of small leather particles remaining due to the inability to ensure complete homogenization, affecting subsequent applications. In contrast, this invention uses a ball milling process, which is more suitable for industrial production. This process has a shorter preparation cycle, a higher extraction rate of natural collagen, and the ball milling process produces more uniform samples with more controllable quality.

[0243] Test Example 1

[0244] The performance testing methods of tissue-like natural collagen composite absorbable sutures prepared in Examples 1-3 and their performance comparison with traditional absorbable sutures (gut sutures, synthetic fiber sutures)

[0245] (1) Determination of linear density, breaking strength and elongation at break

[0246] The tensile strength and elongation at break of a single fiber were measured using a domestically produced YG001A electronic fiber strength tester. The initial fiber length was 20 mm, and the tensile rate was 10 mm / min. Each fiber sample was measured 10 times, and the average value was taken. To determine the linear density of the fiber, the fiber was first cut using a Y171 fiber cutter, and then the mass of 50 fibers with a length of 20 mm was measured using a JN-B precision torque balance. The results are shown in Table 1.

[0247] Table 1. Test results of linear density, tensile strength, and elongation at break of sutures.

[0248] sheep gut sutures 4.2 0.54 25.06 Collagen sutures 4.0 0.55 13.25 Example 1 6.9 0.88 18.56 Example 2 6.6 0.85 14.65 Example 3 7.2 0.93 16.57

[0249] As shown in Table 1, the tissue-like natural collagen composite absorbable suture prepared in this invention has a greater advantage in material strength compared with traditional collagen and sheep intestine absorbable sutures.

[0250] (2) Determination of in vitro degradability

[0251] Preparation of Hanks degradation solution: Dissolve 160g NaCl, 8g KCl, 2g MgSO4·7H2O, and 2g MgCl2·6H2O in 100mL of double-distilled water to obtain solution A. Dissolve 2.8g CaCl2 in 100mL of double-distilled water to obtain solution B. Mix solutions A and B, add double-distilled water to a final volume of 1000mL, and add 2mL of chloroform as a preservative to obtain stock solution A, which is stored at 4℃. Dissolve 3.04g Na2HPO4·12H2O, 1.20g KH2PO4, 20.0g glucose, and 100mL of 4.0g / L phenol red solution in 800mL of double-distilled water to obtain solution C. Add double-distilled water to a final volume of 1000mL, and add 2mL of chloroform as a preservative to obtain stock solution B, which is stored at 4℃. Mix stock solution A, stock solution B and double-distilled water in a volume ratio of 1:1:18 and sterilize at 115℃ for 10 min to obtain Hanks degradation solution.

[0252] Methods: 0.02 g of each suture sample was placed in a test tube, and 10 mL of Hanks degradation solution was added to completely immerse the sample. The test tubes were then sealed and placed in a water bath at 37℃±1℃. The Hanks degradation solution was changed weekly. Samples were taken on days 7, 14, and 21, washed with distilled water, and vacuum dried for 5 hours. The mass of residual fibers was measured. The degradation rate (i.e., percentage of mass loss) was calculated, and the results are shown in Table 2.

[0253] Table 2. Degradation rate test results of sutures

[0254] 7-day degradation rate / % 28.9 15.6 17.8 16.9 17.5 14-day degradation rate / % 36.4 23.3 25.4 23.8 24.6 28-day degradation rate / % 38.5 27.4 29.6 28.4 29.4

[0255] As shown in Table 2, the tissue-like natural collagen composite absorbable suture prepared in this invention has a greater advantage in biodegradability compared with traditional collagen and sheep intestine absorbable sutures.

[0256] (3) Determination of antibacterial activity (shaking method)

[0257] Referring to standard GB / T20944.3, the experimental bacterial strains were standard strains of Staphylococcus aureus and Escherichia coli. The in vitro antibacterial properties of the absorbable sutures prepared in the examples were quantitatively evaluated. The specific experimental steps are as follows:

[0258] (1) Prepare Luria-Bertani (LB) liquid culture medium according to standard GB / T20944.3.

[0259] (2) Prepare Luria-Bertani (LB) solid culture medium according to standard GB / T20944.3.

[0260] (3) Prepare bacterial suspensions according to standard GB / T20944.3, and use culture tubes containing only S. aureus and E. coli as blank controls.

[0261] (4) Weigh 100 mg of the tissue-like natural collagen composite absorbable suture prepared in the example, the sheep intestine suture as a control sample, and the collagen suture, respectively, and put them into a 50 mL centrifuge tube. Sterilize under ultraviolet light for 30 min for later use.

[0262] (5) Dilute the bacterial culture to 10 using sterile phosphate-buffered saline (PBS) solution. 6 CFU / mL, 20 mL of LB liquid medium and 600 μL of diluted bacterial suspension were added to centrifuge tubes, respectively. No sample was added to the blank control group. Centrifuge tubes containing samples of different absorbable sutures were incubated for 18 h using a constant-temperature shaker (ambient temperature: 37℃). The bacterial suspension was then diluted 10-fold with sterile PBS solution, and 1 mL of the diluted solution was carefully spread onto LB solid medium. After this process, the tubes were incubated for 18 h in a constant-temperature incubator (ambient temperature: 37℃), and the colony count was recorded. Colony counts were calculated according to the counting principles of national standard GB4789.2, and bacterial concentration and antibacterial rate were calculated according to standard GB / T20944.3. The results are shown in Table 3.

[0263] Table 3. Results of antibacterial performance test of sutures

[0264] Blank control 109 <![CDATA[10 7 ]]> <![CDATA[1.09×10 8 ]]> / sheep gut sutures 119 <![CDATA[10 7 ]]> <![CDATA[1.05×10 8 ]]> 0 Collagen sutures 112 <![CDATA[10 7 ]]> <![CDATA[6.1×10 7 ]]> 0 Example 1 90 <![CDATA[10 5 ]]> <![CDATA[9.9×10 5 ]]> 99.10％ Example 2 72 <![CDATA[10 4 ]]> <![CDATA[8.45×10 4 ]]> 99.45％ Example 3 88 <![CDATA[10 6 ]]> <![CDATA[1.21×10 6 ]]> 98.87％

[0265] As shown in Table 3, the tissue-like natural collagen composite absorbable suture prepared in this invention has a greater advantage in antibacterial properties compared with traditional collagen and sheep intestine absorbable sutures.

[0266] (4)2. Wound healing speed and scar reduction effect

[0267] The tissue-like natural collagen composite absorbable suture prepared in this example was applied to an emergency animal model of laceration injuries. New Zealand white rabbits were selected, with the wound site set on the spine, approximately 10 cm in length and <20 mm in depth. A control group was prepared using collagen sutures to suture the incision. The healing of the wounds was observed, and the degree of wound healing was used as the evaluation standard. In the observation group, both short-term healing (3 days) and long-term healing (21 days) were good, with a healing rate of 100%. Good short-term healing was defined as no bleeding or exudation from the incision, and no tenderness after 72 hours. Good long-term healing was defined as no induration around the incision, no scarring, and some scars were even barely visible. In the control group, 90% of the animals healed within 3 days, 10% experienced suture breakage, and some animals developed induration at the incision site. Therefore, the absorbable suture prepared in this patent has a greater advantage in promoting wound healing compared to traditional absorbable sutures. Three months after suturing, the observation and experimental groups were observed, and the scar formation of the wounds was assessed and compared using the Vancouver Scar Scale. This scale includes four dimensions, with scores ranging from 0 to 15: 0 points for no scar, 1-5 points for mild scarring, 6-10 points for moderate scarring, and 11-15 points for severe scarring. In the observation group, 24 rabbits had no scars, and 16 had mild scarring, with an average score of 1.2 points. In the control group, 12 rabbits had no scars, 27 had mild scarring, and 1 had moderate scarring, with an average score of 2.175 points. This demonstrates that the novel absorbable medical suture invented in this patent also promotes scar reduction in wounds.

[0268] Test Example 2

[0269] Performance testing of collagen raw materials (medical-grade tissue-like natural collagen prepared in Example 4, antigen-free collagen aggregates prepared in Comparative Example 1, and commercially available molecular-grade collagen).

[0270] (1) The results of collagen extraction rate and impurity protein content of the raw materials are shown in Table 4.

[0271] Table 4. Results of collagen extraction rate and impurity protein content of raw materials for adhesives.

[0272] Comparative Example 1 75％ 0.8wt% Example 4 92％ 0.4wt%

[0273] As shown in Table 4, compared with Comparative Example 1, the collagen extraction rate of the medical-grade tissue natural collagen prepared by the present invention is significantly improved, and the content of impurity proteins is significantly reduced.

[0274] (2) The weight loss of the adhesive raw materials in different temperature ranges is shown in Table 5.

[0275] Table 5. Weight loss of adhesive raw materials in different temperature ranges

[0276]

[0277] As shown in Table 5, compared with Comparative Example 1 and collagen, the medical-grade tissue-like natural collagen prepared by the present invention has a lower weight loss rate and better thermal stability and structural stability in the temperature range of 50-800℃.

[0278] (3) 30-day degradation rate test method: Degradation in collagenase solution. The specific operation is as follows: Bacterial type I collagenase is dissolved in PBS buffer to prepare a type I collagenase degradation solution with a concentration of 2 mL / mg (1 U / mL). The samples are freeze-dried and then soaked in the degradation solution for 30 days. The degradation experiment is then carried out in a 37℃ constant temperature biochemical incubator.

[0279] Tensile strength test method: The collagen sample is poured into a polytetrafluoroethylene mold to form a film, and then the tensile strength of the sample is tested using a universal tensile testing machine.

[0280] Method for testing hemostasis time: Rabbit ear central artery hemostasis model.

[0281] The hemostatic effect, degradation rate and tensile strength of the adhesive raw materials are shown in Table 6.

[0282] Table 6 Results of hemostasis, degradation and tensile strength of adhesive raw materials

[0283] Example 4 68s 68％ 3.2MPa Comparative Example 1 116s 89％ 2.4MPa collagen 182s 100％ 0.9MPa

[0284] As shown in Table 6, compared with Comparative Example 1 and collagen, the medical-grade tissue-like natural collagen prepared by this invention has a shorter hemostasis time and better hemostasis effect; a lower degradation rate and slower degradation speed after 30 days; and higher tensile strength.

[0285] (4) MTT test

[0286] Experimental Methods: Single-cell suspensions were prepared using culture medium containing 10% fibroblasts. 1000–10000 cells were seeded into each well of a 96-well plate (200 μL per well). Cells were cultured under standard conditions for 3–5 days. After the culture period, 10 μL of MTT solution was added to each well for an additional 4 hours of incubation. The culture was then terminated, and the supernatant was carefully aspirated from the wells. For suspended cells, centrifugation was required before aspirating the supernatant. Next, 100 μL of dimethyl sulfoxide (DMSO) was added to each well, and the mixture was shaken for 10 minutes to dissolve any crystals. Finally, the absorbance of each well was measured at 490 nm using an ELISA reader, and the results were recorded. A cell growth curve was plotted with time on the x-axis and absorbance on the y-axis to assess cell growth.

[0287] Figure 4 The MTT assay results of collagen, antigen-free collagen aggregates prepared in Comparative Example 1, and medical-grade tissue-like natural collagen prepared in Example 4 show that the medical-grade tissue-like natural collagen prepared in this invention provides a more suitable growth environment for cells, exhibits significant advantages in promoting fibroblast proliferation and growth, and provides a more ideal growth microenvironment for cells.

[0288] (5) 24-hour scratch test

[0289] Experimental method: Using a marker pen, draw evenly horizontal lines on the back of a six-well plate with the aid of a ruler, as a positioning reference for subsequent experiments; inoculate each well of the six-well plate with 3 × 10⁶ seeds. 5 Cells were cultured at 2 mL per well. After 24 h of cell culture, a 200 μL pipette tip was used to make scratches along pre-marked lines on the cell layer to create "wounds." After scratching, the culture supernatant was aspirated, and the cells were washed 2-3 times with PBS to remove the scratched cells. The old culture medium was discarded, and either drug-containing medium or serum-free medium was added according to the experimental groups. The cells were then incubated at 37°C in a 5% CO2 incubator. Cells were harvested at predetermined time points such as 0 h and 24 h, and the changes in scratch width at the same locations were observed and recorded under a microscope. Photographs were also taken to observe changes in cell migration.

[0290] Figure 5 This is a 24-hour scratch test result image of collagen. Figure 6 This image shows the 24-hour scratch test results of the antigen-free collagen aggregates prepared in Comparative Example 1. Figure 7 This is a 24-hour scratch image of the medical-grade tissue-like natural collagen prepared in Example 4. Figures 5-7 It can be seen that, compared with the antigen-free collagen aggregates prepared by collagen and Comparative Example 1, the medical-grade tissue-like natural collagen prepared by the present invention can better promote cell growth and proliferation, and is more conducive to wound tissue regeneration and scar formation.

[0291] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A tissue-like natural collagen composite absorbable suture, comprising medical-grade tissue-like natural collagen, epoxidized modified chitosan, molybdenum dioxide nanoparticles, and sodium alginate; The method for preparing the medical-grade tissue natural collagen includes the following steps: (1) Remove the subcutaneous tissue from the animal skin, soak it in physiological saline, and obtain pretreated animal skin; (2) The pretreated animal skin is degreased to obtain degreased animal skin; (3) The defatted animal hide is subjected to hair removal treatment to obtain a hairless animal hide; (4) The hairless animal skin is subjected to a de-swelling treatment to obtain a de-swollen animal skin; (5) The de-swelled animal skin is subjected to acid swelling treatment to obtain acid-swollen animal skin; (6) The acid-swollen animal skin is crushed, the pH value is adjusted to 7~7.4, solid-liquid separation is performed to obtain solid components, the solid components are washed with water and dried to obtain medical-grade tissue natural collagen; In step (4), the swelling removal treatment includes: adding a first portion of water and inorganic salts to the dehaired animal skin for a first swelling removal treatment, adding a second portion of water to adjust the pH value to 4~4.5, adding acidic lipase for a second swelling removal treatment, and adding acidic protease for a third swelling removal treatment. In step (5), the acid swelling treatment includes: adding water to the de-swelled animal skin, adjusting the pH value to 2.8~3.0, stirring the acid swelling treatment, and then letting it stand for acid swelling treatment; The mass ratio of the medical-grade tissue natural collagen to the epoxidized modified chitosan is 10:0.25~1.5; The mass ratio of the medical-grade tissue natural collagen to molybdenum dioxide nanoparticles is 10:0.01~0.1; The mass ratio of the medical-grade tissue natural collagen to sodium alginate is 10:0.25~1.5; The molybdenum dioxide nanoparticles include monoclinic molybdenum dioxide nanoparticles. The epoxidized chitosan includes epoxidized chitosan obtained by epoxidizing chitosan with ethylene glycol diglycidyl ether.

2. The tissue-like natural collagen composite absorbable suture according to claim 1, characterized in that, In step (2), the degreasing treatment includes: adding a degreasing agent and water to the pretreated animal skin for degreasing treatment; The mass ratio of the pretreated animal hide to the defatting agent is 1:0.01~0.04; The degreasing agent includes one or more of alkyl polyglycosides, laundry detergent, sodium lauryl sulfate, and fatty alcohol polyoxyethylene ether; The mass-to-volume ratio of the pretreated animal hide to water is 1 kg: 1.5~3 L; The degreasing treatment is carried out at a temperature of 30~37℃ for 2~5 hours. The degreasing process also includes washing with water; In step (3), the hair removal treatment includes: adding the defatted animal skin, water, polyoxyethylene ether and ferrous salt for the first hair removal treatment, adding alkaline amine for the second hair removal treatment, adding alkaline reagent for the third hair removal treatment, adding oxidant for the fourth hair removal treatment, and adding dilute alkaline reagent aqueous solution for the fifth hair removal treatment. The mass-to-volume ratio of the defatted animal skin to water is 1 kg: 1~2 L; The polyoxyethylene ether includes fatty alcohol polyoxyethylene ether; the mass ratio of the pretreated animal skin to the polyoxyethylene ether is 1:0.3~0.6; The ferrous salt includes ferrous sulfate and / or ferrous ammonium sulfate; the mass ratio of the pretreated animal skin to the ferrous salt is 1:0.3~0.6; The first hair removal treatment takes 90-150 minutes; The alkanolamine includes one or more of triethanolamine, monoethanolamine, and diethanolamine; the mass ratio of the pretreated animal skin to the alkanolamine is 1:0.01~0.03; The second hair removal treatment takes 10-20 minutes; The alkaline reagent includes alkali metal hydroxides and / or alkali metal carbonates; the mass ratio of the pretreated animal skin to the alkaline reagent is 1:0.035~0.045; The third hair removal treatment takes 15-25 minutes; The oxidant includes one or more of hydrogen peroxide, sodium perborate, and sodium percarbonate; the mass ratio of the pretreated animal skin to the oxidant is 1:0.06~0.08; The fourth hair removal treatment takes 3-4 hours; The alkaline reagent in the dilute alkaline aqueous solution includes alkali metal hydroxides and / or alkali metal carbonates; the mass fraction of the dilute alkaline reagent aqueous solution is 0.3~0.8%; the time of the fifth hair removal treatment is 4~6 hours; The hair removal process also includes washing with water; In step (4), the mass-to-volume ratio of the pretreated animal skin to the first portion of water is 1 kg: 0.8~1 L; The inorganic salt includes one or more of sodium bisulfite, ammonium sulfate, ammonium chloride, and ammonium acetate; the inorganic salt accounts for 0.05-0.2% of the mass of the pretreated animal skin. The temperature of the first deswelling treatment is 28~35℃, the time is 50~60min, and the final pH value is 8~8.5; The mass-to-volume ratio of the pretreated animal hide to the second portion of water is 1 kg: 1 L to 4 L; The acidic lipase accounts for 0.1-0.3% of the pretreated animal skin mass; the enzyme activity of the acidic lipase is 50,000-60,000 units / g. The second deswelling treatment is performed at a temperature of 28-35℃ for 15-20 minutes. The acidic protease accounts for 0.1-0.3% of the pretreated animal skin mass; the enzyme activity of the acidic protease is 80,000-100,000 units / g. The third deswelling treatment is performed at a temperature of 38~42℃ for 2~5 hours. The swelling reduction treatment also includes washing with water; In step (5), the mass-to-volume ratio of the pretreated animal skin to water is 1 kg: 1~2 L; The stirring acid swelling treatment time is 30~60 min; The static acid swelling treatment time is 6-8 hours; The acid swelling treatment also includes water washing; In step (6), the crushing includes ball milling, wherein the ball-to-material ratio of the ball milling is 1:1~5, the rotation speed is 200~600 r / min, and the time is 1~3 h; The drying includes freeze-drying; The drying process also includes disinfection and sterilization.

3. The tissue-like natural collagen composite absorbable suture according to claim 1, characterized in that, The preparation method of the epoxidized modified chitosan includes the following steps: Chitosan, ethylene glycol diglycidyl ether, and water were mixed and epoxidized to obtain epoxidized chitosan.

4. A method for preparing the tissue-like natural collagen composite absorbable suture according to any one of claims 1 to 3, comprising the following steps: Medical-grade tissue-derived natural collagen, epoxidized chitosan, molybdenum dioxide nanoparticles, sodium alginate, and water are blended to obtain a spinning solution; the blending includes ultrasonic mixing. The spinning solution is spun to obtain a tissue-like natural collagen composite absorbable suture.

5. The preparation method according to claim 4, characterized in that, The mass ratio of the medical-grade tissue natural collagen to the epoxidized modified chitosan is 10:0.25~1.5; The mass ratio of the medical-grade tissue natural collagen to molybdenum dioxide nanoparticles is 10:0.01~0.1; The mass ratio of the medical-grade tissue natural collagen to sodium alginate is 10:0.25~1.5; The concentration of medicinal grade tissue natural collagen in the spinning solution is 12-25 wt%.

6. The preparation method according to claim 4 or 5, characterized in that, The spinning process conditions include: the coagulation bath is saturated sodium sulfate; the pressure is 0.05~0.2MPa; the spinning solution temperature is room temperature; the coagulation temperature is 25~35℃; and the winding speed is 8~15m / min.

7. The use of the tissue-like natural collagen composite absorbable suture according to any one of claims 1 to 3 or the tissue-like natural collagen composite absorbable suture prepared by the preparation method according to any one of claims 4 to 6 in the preparation of tissue engineering materials, regenerative medicine materials or implantable medical devices.

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