A metal ion enhanced antibacterial silk protein fiber and its preparation method

Abstract

The invention discloses a metal ion enhanced antibacterial silk protein fiber and a preparation method thereof, comprising the following steps: S1: degumming silk in an alkaline salt solution, drying naturally and then drying to obtain degummed silk; S2: preparing a dissolving solution containing transition metal ions, calcium ions and an organic solvent, dissolving the degummed silk in the dissolving solution to obtain a spinning solution of a certain concentration; S3: squeezing or sucking the spinning solution into a multi-channel spinning chip through a metering device; S4: squeezing the spinning solution from an extrusion port through the chip into a coagulation bath containing a coagulant and a toughening agent of a certain concentration to form multiple strands of fiber fibrils; S5: after the multiple strands of fiber fibrils are out of the coagulation bath, they are subjected to differential stretching between stretching rollers, and finally a metal ion enhanced antibacterial silk protein fiber is obtained on a collecting roller. According to the invention, not only a high-performance regenerated fiber material is provided, but also an effective way for the resource utilization of waste silk is provided.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of bio-protein fibers, and particularly to a metal ion enhanced antibacterial silk protein fiber and a preparation method thereof. Background Art

[0002] Silk is a kind of protein fiber formed by silkworms spinning silk, which has excellent biocompatibility, degradability and other advantages, and is widely used in the fields of biomedicine, industry and agriculture, such as surgical sutures, artificial ligaments, silk quilts, silk clothing and other aspects. Silk can be mass-produced by artificial breeding methods. It can also be seen from the ancient Silk Road that silk and its subsequent processing are traditional textile technologies in China and also a manifestation of Chinese culture. However, as a surgical suture, the degradation rate of silk is far slower than that of regenerated silk, which undoubtedly limits its use in biomedicine; on the other hand, some waste silk will also be generated during the weaving process and the disposal and recycling of waste silk clothes. If these waste silk are directly discarded, it will undoubtedly cause waste of resources and environmental hazards. Therefore, how to optimize the rapid degradability of silk and the recycling of waste silk has become a key scientific and technological problem that needs to be solved at present. Summary of the Invention

[0003] The purpose of the present invention is to provide a metal ion antibacterial enhanced silk protein fiber and a preparation method thereof, so as to solve the problem that the silk in the prior art cannot simultaneously meet the requirements of rapid degradation and waste silk recycling.

[0004] In order to achieve the above invention purpose, the present invention adopts the following technical solutions:

[0005] According to the first aspect of the present invention, a preparation method of a metal ion enhanced antibacterial silk protein fiber is provided, including the following steps: S1: Degumming the silk obtained after removing the pupae from natural cocoons in an alkaline salt solution, naturally drying and then drying to obtain degummed silk; S2: Preparing a dissolution solution containing transition metal ions, calcium ions, and an organic solvent, and dissolving the degummed silk in the dissolution solution to obtain a spinning solution with a certain concentration; the organic solvent is one or more of formic acid, hexafluoroisopropanol, and trifluoroacetic acid, and the transition metal ions are Fe 3+ , Zn 2+ , Mn 2+ , Cu 2+ , Mg 2+One of the following; the concentration of the transition metal ion is 0.1-1.0%, and the concentration of calcium ion is 1-10%; S3: Squeeze or suck the spinning solution into a multi-channel spinning chip through a metering device; S4: The spinning solution passes through the chip and is extruded from the extrusion port into a coagulation bath containing a certain concentration of coagulant and toughening agent to form multiple fiber fibrils; S5: After the multiple fiber fibrils leave the coagulation bath and are differentially stretched between the stretching rollers, a metal ion-enhanced antibacterial silk protein fiber is finally obtained on the collecting roller.

[0006] Preferably, in step S1, the solid-liquid mass ratio of degumming is 1:10-1:1000, and the duration of degumming is 10-120 min.

[0007] Preferably, in step S2, the concentration of the transition metal ion in the dissolution solution used is 0.5%, and the concentration of calcium ion is 5%.

[0008] Preferably, in step S2, the dissolution solution used contains 0.5% by mass of ferric chloride, 5% by mass of calcium chloride, and the organic solvent is formic acid.

[0009] Preferably, in step S2, the dissolution solution used contains 0.5% by mass of manganese chloride, 5% by mass of calcium chloride, and the organic solvent is formic acid.

[0010] Preferably, in step S4, by volume ratio, the coagulation bath contains 50-60% ethanol and 3-5% glycerol.

[0011] Preferably, in step S5, the number of strands of the multiple fiber fibrils is 2-500.

[0012] Preferably, in step S1, the silk raw material is silk obtained after removing pupae from natural cocoons or waste silk.

[0013] Preferably, in step S5, the stretching multiple of the differential stretching is 4-10.

[0014] Preferably, the natural cocoon in step S1 is one or more of mulberry cocoons, tussah cocoons, etc., and most preferably a mulberry cocoon.

[0015] Preferably, the solute of the alkaline salt solution is one or more of sodium carbonate and sodium bicarbonate, and most preferably sodium carbonate; the concentration of the alkaline salt solution is 0.01%-1.00%, and most preferably 0.05%.

[0016] Preferably, the duration of degumming is 10-120 min, and most preferably 30 min.

[0017] Preferably, the degummed silk fibroin fiber in step S2 is the dried degummed silk after natural drying; the degumming rate of the degummed silk fibroin fiber is 20%-35%, more preferably 25%-30%.

[0018] The organic solvent is one or more of formic acid, hexafluoroisopropanol, and trifluoroacetic acid, and most preferably formic acid.

[0019] Preferably, the metering device in step S3 is a device such as a micro-injection pump, a plunger pump, or a metering pump, and most preferably a plunger pump; the multi-channel spinning chip is a microfluidic device containing a main channel and multiple branch channels; the material of the chip is stainless steel or aluminum alloy resistant to organic dissolution.

[0020] Preferably, the stretching rollers for differential stretching in step S5 are stainless steel rollers with the same diameter but different rotation speeds; the stretching multiple for differential stretching is 1-20, more preferably 4-10; the regenerated silk fibroin multifilament long fiber is composed of multiple regenerated silk fibroin fiber monofilaments; the number of strands of the multi-strand fiber fibril is 2-500, more preferably 5-50; the long fiber is a regenerated silk fibroin fiber with a length greater than 1000m.

[0021] According to a preferred embodiment of the present invention, a dissolution solution is prepared according to the ratio of 0.5% by mass of ferric chloride and 5% by mass of calcium chloride in the solvent. According to the volume ratio, a coagulation bath with an ethanol concentration of 50% and a glycerol concentration of 5% is prepared. After being fully stretched between the differential stretching rollers with a total stretching multiple of 4 times, the metal ion-enhanced antibacterial silk fibroin fiber is collected on the collecting roller 6, and mechanical property tests are carried out. Its stress is as high as 686.4±33.4 MPa, and the strain is 28.3±4.6%.

[0022] According to the second aspect of the present invention, there is provided a metal ion-enhanced antibacterial silk fibroin fiber prepared by the above method. The metal ion-enhanced antibacterial silk fibroin fiber has certain antibacterial properties and can effectively inhibit the growth and reproduction of microorganisms, including Escherichia coli and Staphylococcus aureus, and the antibacterial rate is ≥99.99%.

[0023] For the metal ion-enhanced antibacterial silk fibroin fiber prepared by the method of the present invention, the stress of the mechanical property is 50-1000 MPa, more preferably 100-800 MPa, and the strain is 5%-100%, more preferably 10%-80%.

[0024] It should be understood that, in addition to fibers directly derived from plants and animals, the methods for artificially preparing fibers can be roughly divided into melt spinning, dry spinning and wet spinning. Since protein fibers such as silk are not resistant to high temperatures, wet spinning is undoubtedly the only choice for preparing regenerated silk. The present invention dissolves silk in a specific solvent, and then extrude the spinning solution into a coagulation bath. After the fibers are out of the coagulation bath, they are oriented and shaped by post-stretching to obtain regenerated silk fibers with certain mechanical properties. In particular, by optimizing the process parameters of the spinning solution and the coagulation bath and steps such as doping with metal ions, regenerated silk protein fibers comparable to natural silk are obtained, which optimizes the degradation performance while also having a positive impact on resource recycling and environmental protection.

[0025] The key invention of the present invention is mainly that, by using organic solvents such as formic acid to dissolve silk, calcium ions are added as a dissolution promoter, and in particular, a certain amount of transition metal ions are added as a structural reinforcing agent to dissolve silk well and obtain a spinning solution with a certain viscosity. Then the spinning solution is extruded into a coagulation bath through a microfluidic device containing a main channel and multiple branch channels to obtain regenerated silk fibroin multifilament fibrils, and the number of monofilaments in the multifilament is determined by the number of branch channels of the microfluidic device, and the number of monofilaments is determined by the number of branches. The multifilament fibrils are coagulated into primary fibers with a certain solid morphology after solvent exchange in the coagulation bath, and the primary fibers are differentially stretched between differential stretching rollers, and the solvent volatilizes during the stretching process, and finally the regenerated silk fibroin multifilament long fibers with certain mechanical properties and antibacterial properties are collected on the collecting roller. When the spinning solution is sufficient, the fiber can be stretched continuously for more than 24 hours, and the purpose of continuous mass production can be achieved.

[0026] In summary, the present invention uses organic solvents such as formic acid and combines the dissolution-promoting and coordination-enhancing effects of metal ions to dissolve and spin silk in a one-step method, and winds to obtain regenerated silk fibroin fibers. The process is simple and convenient, and the mechanical properties of the obtained regenerated silk fibroin fibers are close to those of natural silk, providing a new technical method for the reuse of waste silk. The prepared regenerated silk fibroin fibers have good degradability, excellent mechanical properties and antibacterial properties, and can be further applied in the biomedical field. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the experimental device, where 1-spinning solution inlet; 2-multi-channel chip; 3-coagulation bath; 4-first stretching roller; 5-second stretching roller; 6-collecting roller;

[0028] Figure 2 is a scanning electron microscope cross-sectional view of the regenerated silk fibroin multifilament long fiber of the present invention (Example 4);

[0029] Figure 3 The fiber stress-strain curve diagram of Example 1 in the present invention;

[0030] Figure 4 The fiber stress-strain curve diagram of Example 2 in the present invention;

[0031] Figure 5 The fiber stress-strain curve diagram of Example 3 in the present invention;

[0032] Figure 6 The fiber stress-strain curve diagram of Example 4 in the present invention;

[0033] Figure 7 The fiber stress-strain curve diagram of Example 5 in the present invention. Detailed implementation manners

[0034] The following further describes the present invention in conjunction with specific embodiments. It should be understood that the following embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0035] Example 1

[0036] According to this embodiment, a preparation process of metal ion enhanced antibacterial silk fibroin fiber is provided. As shown in Figure 1 The preparation process is described as follows:

[0037] 1) Silk degumming

[0038] Cut the pupa-free silk into pieces, put the silk into a 0.05% sodium carbonate solution, boil the degummed silk, rinse it with purified water under running water and then dry it. After drying, weigh the mass of the degummed silk, and calculate that the degumming rate is 27.6%.

[0039] 2) Spinning solution preparation

[0040] Prepare a dissolution solution according to the proportion that the mass fraction of ferric chloride in the solvent is 0.5% and the mass fraction of calcium chloride is 5%. The specific data is as follows: Weigh 0.225 g of ferric chloride, 2.0 g of calcium chloride, and 37.9 g of formic acid, stir well to obtain a clear and transparent dissolution solution. Add 6 g of degummed silk to the dissolution solution, and fully dissolve it to obtain a spinning solution with a concentration of 13%.

[0041] 3) Coagulation bath preparation

[0042] Prepare a coagulation bath with an ethanol concentration of 50% and a glycerol concentration of 5% by volume ratio.

[0043] 4) Spinning

[0044] As Figure 1As shown, a 10-channel multi-channel chip 2 is used, and a plunger pump is used as a power source to suck the spinning liquid from the spinning liquid inlet 1 into the chip. After passing through the fine needle at the rear end of the chip, the spinning liquid is squeezed into the coagulation bath 3 to form nascent fibers. After solvent exchange in the coagulation bath, multiple nascent fibers are stretched onto the first stretching roller 4, pass through the second stretching roller 5, and are fully stretched between differential stretching rollers with a total stretching multiple of 4 times, and then regenerated silk fibroin multifilament long fibers with a certain stress strain are obtained on the collecting roller 6.

[0045] 5) Test characterization

[0046] The mechanical properties of the obtained regenerated silk fibroin multifilament fiber were tested, and the test results are as follows: Figure 3 As shown, the stress is 686.4±33.4MPa and the strain is 28.3±4.6%. The antibacterial performance of the material reaches more than 70%.

[0047] Example 2

[0048] 1) Silk degumming

[0049] The silk was cut into pieces after the pupae were removed, and the silk was put into a 0.05% sodium carbonate solution, and the degummed silk was rinsed with purified water and dried. After drying, the mass of the degummed silk was weighed, and the degumming rate was calculated to be 28.9%.

[0050] 2) Spinning solution preparation

[0051] The dissolving solution was prepared according to the ratio of 0.5% zinc chloride mass fraction and 5% calcium chloride mass fraction in the solvent. The specific data are as follows: 0.188g zinc chloride, 2.0g calcium chloride, 38.0g formic acid were weighed and stirred thoroughly to obtain a clear and transparent dissolving solution. 6g degummed silk was added to the dissolving solution and a spinning solution with a concentration of 13% was obtained after sufficient dissolution.

[0052] 3) Preparation of coagulation bath

[0053] Prepare a coagulation bath with an ethanol concentration of 50% and a glycerol concentration of 5% by volume, and fill a coagulation bath tank with a volume of 7 L and a length of 40 cm.

[0054] 4) Spinning

[0055] A 10-channel aluminum alloy chip is used, and a plunger pump is used as the power source to suck the spinning into the chip. After passing through the fine needle at the rear end of the chip, the spinning solution is squeezed into the coagulation bath to form primary fibers. After solvent exchange in the coagulation bath, multiple primary fibers are stretched onto the first stretching roller. After being fully stretched between differential stretching rollers with a total stretching multiple of 4 times, regenerated silk fibroin multifilament long fibers with a certain stress strain are obtained on the collecting roller.

[0056] 5) Test characterization

[0057] The mechanical properties of the obtained regenerated silk fibroin multifilament fiber were tested, and the test results are as follows: Figure 4 As shown, the stress is 401.1±26.5MPa and the strain is 41.3±8.5%. The antibacterial performance of the material reaches more than 50%.

[0058] Example 3

[0059] 1) Silk degumming

[0060] The silk was cut into sheets after the pupae were removed, and the silk was placed in a 0.05% sodium carbonate solution, and the degummed silk was rinsed with purified water and dried. After drying, the mass of the degummed silk was weighed, and the degumming rate was calculated to be 28.1%.

[0061] 2) Spinning solution preparation

[0062] The dissolving solution was prepared according to the ratio of 0.5% manganese chloride mass fraction and 5% calcium chloride mass fraction in the solvent. The specific data are as follows: 0.174g manganese chloride, 2.0g calcium chloride, 38.0g formic acid were weighed and stirred thoroughly to obtain a clear and transparent dissolving solution. 6g degummed silk was added to the dissolving solution and a spinning solution with a concentration of 13% was obtained after sufficient dissolution.

[0063] 3) Preparation of coagulation bath

[0064] A coagulation bath with a volume ratio of 60% isopropanol and 2% glycerol was prepared.

[0065] 4) Spinning

[0066] A 10-channel aluminum alloy chip is used, and a plunger pump is used as the power source to squeeze the spinning into the chip. After passing through the fine needle at the rear end of the chip, the spinning solution is squeezed into the coagulation bath to form primary fibers. After solvent exchange in the coagulation bath, multiple primary fibers are stretched onto the first stretching roller. After being fully stretched between differential stretching rollers with a total stretching multiple of 4.5 times, regenerated silk fibroin multifilament long fibers with a certain stress strain are obtained on the collecting roller.

[0067] 5) Test characterization

[0068] The mechanical properties of the obtained regenerated silk fibroin multifilament fiber were tested, and the test results are as follows: Figure 5 As shown, the stress is 503.5±53.0MPa and the strain is 25.5±7.0%. The antibacterial performance of the material reaches more than 20%.

[0069] Example 4

[0070] 1) Silk degumming

[0071] Cut the pupal-free silk into pieces, put the silk into a 0.05% sodium carbonate solution, and after boiling and degumming, rinse the silk with purified water flowing water and then dry it. After drying, weigh the mass of the degummed silk, and calculate that the degumming rate is 28.3%.

[0072] 2) Preparation of spinning solution

[0073] Prepare a dissolution solution according to the ratio of 0.5% mass fraction of copper chloride and 5% mass fraction of calcium chloride in the solvent. The specific data is as follows: Weigh 0.186 g of copper chloride, 1.7 g of calcium chloride, and 32.1 g of formic acid, and after stirring well, obtain a clear and transparent dissolution solution. Add 6 g of degummed silk to the dissolution solution, and after fully dissolving, obtain a spinning solution with a concentration of 15%.

[0074] 3) Preparation of coagulation bath

[0075] Prepare a coagulation bath with an ethanol concentration of 60% and a glycerol concentration of 3% according to the volume ratio.

[0076] 4) Spinning

[0077] Use a 7-channel aluminum alloy chip, with a micro-injection pump as the power source, extrude the spinning solution into the chip. After passing through the fine needle at the rear section of the chip, the spinning solution is extruded into the coagulation bath to form primary fibers. After solvent exchange of multiple primary fibers in the coagulation bath, they are drawn to the first stretching roller, and after being fully stretched between the differential stretching rollers with a total stretching multiple of 8.3 times, a regenerated silk fibroin multifilament long fiber with a certain stress-strain is obtained on the collecting roller. The cross-section of the regenerated silk fibroin multifilament long fiber observed by scanning electron microscope is as Figure 2 shown.

[0078] 5) Testing and characterization

[0079] Perform mechanical property tests on the obtained regenerated silk fibroin multifilament long fiber. The test results are as Figure 6 shown, where the stress is 494.7 ± 32.3 MPa and the strain is 24.1 ± 3.6%. The antibacterial property of the material reaches more than 99.99%.

[0080] Example 5

[0081] 1) Silk degumming

[0082] Cut the pupal-free silk into pieces, put the silk into a 0.05% sodium carbonate solution, and after boiling and degumming, rinse the silk with purified water flowing water and then dry it. After drying, weigh the mass of the degummed silk, and calculate that the degumming rate is 28.3%.

[0083] 2) Preparation of spinning solution

[0084] Prepare a dissolution solution according to the ratio of 0.5% by mass of magnesium chloride and 5% by mass of calcium chloride in the solvent. After sufficient stirring, a clear and transparent dissolution solution is obtained. Add degummed silk to the dissolution solution, and after sufficient dissolution, a spinning solution with a concentration of 15% is obtained.

[0085] 3) Preparation of coagulation bath

[0086] Prepare a coagulation bath with an ethanol concentration of 60% and a glycerol concentration of 3% by volume ratio.

[0087] 4) Spinning

[0088] Use a 7-channel aluminum alloy chip, with a micro-injection pump as the power source, extrude the spinning solution into the chip. After passing through the fine needle at the rear section of the chip, the spinning solution is extruded into the coagulation bath to form nascent fibers. After solvent exchange of multiple nascent fibers in the coagulation bath, they are drawn to the first stretching roller, and after being fully stretched between differential stretching rollers with a total stretching multiple of 6.5 times, regenerated silk fibroin multifilament long fibers with a certain stress-strain are obtained on the collecting roller.

[0089] 5) Testing and characterization

[0090] Conduct mechanical property tests on the obtained regenerated silk fibroin multifilament long fibers. The test results are as Figure 7 shown, where the stress is 598.9 ± 29.7 MPa and the strain is 27.8 ± 6.7%.

[0091] The above is only the preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Various changes can be made to the above embodiments of the present invention. All simple, equivalent changes and modifications made according to the claims and the content of the specification of the present invention application fall within the scope of the claims of the present invention patent. The content not described in detail in the present invention is all conventional technical content.

Claims

1. A method for preparing metal ion-reinforced antibacterial silk protein fiber, characterized in that: The following steps are involved: S1: degumming the silk in an alkaline salt solution, drying it naturally, and obtaining degummed silk; S2: preparing a dissolving solution containing transition metal ions, calcium ions and an organic solvent, and dissolving the degummed silk in the dissolving solution to obtain a spinning solution of a certain concentration; the organic solvent is one or more of formic acid, hexafluoroisopropanol and trifluoroacetic acid, the transition metal ions are FeCl3 or CuCl2; the concentration of the transition metal ions is 0.1-1.0%, and the concentration of the calcium ions is 1-10%; S3: The spinning solution is squeezed or sucked into the multi-channel spinning chip through a metering device; S4: the spinning solution is squeezed from the extrusion port through the chip into a coagulation bath containing a certain concentration of coagulant and toughening agent to form a plurality of fiber fibrils, wherein the coagulation bath contains 50-60% ethanol and 3-5% glycerol by volume; S5: After the multi-strand fiber fibrils come out of the coagulation bath, they are subjected to differential stretching between stretching rollers, wherein the stretching multiple of the differential stretching is 4-10, and finally a metal ion-reinforced antibacterial silk protein fiber is obtained on a collecting roller.

2. The preparation method according to claim 1, characterized in that: In step S1, the concentration of the alkaline salt solution is 0.01%-1.00%.

3. The preparation method according to claim 1, characterized in that: In step S1, the solid-liquid mass ratio of the degumming is 1:10-1:1000, and the degumming lasts for 10-120 minutes.

4. The preparation method according to claim 1, characterized in that: In step S2, the concentration of transition metal ions in the used dissolving solution is 0.5%, and the concentration of calcium ions is 5%.

5. The preparation method according to claim 1, characterized in that: In step S2, the dissolving solution used contains 0.5% by mass of ferric chloride, 5% by mass of calcium chloride, and the organic solvent is formic acid.

6. The preparation method according to claim 1, characterized in that: In step S1, the silk raw material is natural silk or waste silk obtained after natural silk cocoons are de-pupaed, and the natural silk cocoons are one or both of mulberry silk cocoons and tussah silk cocoons.

7. A metal ion-reinforced antibacterial silk protein fiber prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The transition metal ions come from CuCl2. The metal ion-enhanced antibacterial silk protein fiber has certain antibacterial properties and can effectively inhibit the growth and reproduction of microorganisms. The microorganisms include: Escherichia coli and Staphylococcus aureus, and the antibacterial rate is ≥99.99%.

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