A stent weaving method and a stent woven using the method

Abstract

The application provides a stent weaving method and a stent woven by the method, the bending performance of the stent is better by improving the weaving method of the existing stent, adopting a spiral downward weaving method, and only one row of cross points between two rows of hook points. The application also improves the performance of the nickel-titanium shape memory alloy, the surface of the nickel-titanium shape memory alloy is coated with a calcium phosphate crystal film, and then a composite coating is coated, the microcrystalline layer of the application is uniformly distributed, the composite coating has high compatibility, and through the synergistic effect, the mechanical stability and the heat insulation effect of the nickel-titanium shape memory alloy are improved. The comprehensive performance of the stent prepared by improving the weaving method and the weaving material is significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of medical device technology, specifically relating to a stent weaving method and a stent woven using this method. Background Technology

[0002] Internal stent placement is widely used due to its significant therapeutic effects, simple and convenient operation, and minimal trauma. Stents made of flexible and expandable materials are widely used in the medical field, mainly to prevent narrowing of various organs and to facilitate the flow of substances in the body. Examples include the dilation of the digestive tract, the dilation of extrahepatic bile ducts, and esophageal obstruction.

[0003] In existing technologies, this type of stent uses a hook and cross braiding method. This type of stent has good expansion performance and is suitable for stenotic or obstructive sites. However, this method has poor flexibility, making it inconvenient to use in certain curved sections of the digestive system. (See stent illustration). Figure 1 and Figure 2 The mechanical properties, thermal insulation, and compatibility of nickel-titanium shape memory alloy braided supports used in existing technologies urgently need further improvement. Summary of the Invention

[0004] The purpose of this invention is to provide a bracing method and a bracing woven using this method, which improves the existing bracing method by adopting a spiral downward bracing method with only one row of cross points between two rows of hook points, resulting in better bending performance of the bracing.

[0005] This invention provides a braiding method for a support structure, the braiding method comprising the following steps:

[0006] Step 1: On the cylindrical fixture, install detachable cylindrical pins, evenly distributed at appropriate positions along the circumference and length; use two wires for weaving, the first wire (wire 1) weaves half of the bracket, and the second wire (wire 2) weaves the other half of the bracket. The first wire and the second wire are the main wires used for braiding the bracket, and the third wire (wire 3) and the fourth wire (wire 4) are the auxiliary wires for braiding the bracket; install the braiding fixture and insert the pins at the corresponding positions on the fixture;

[0007] Step 2: Leave 1600mm for the back braiding head of line 1. Start braiding from the main body end (01.01) until the main body end (01.34). The developing ring is braided to the middle section of the support at the marked position.

[0008] Step 3: Leave 1600mm for the other end of line 2 and start weaving from the starting point of the main body (16.34). Follow these principles: the overlapping order of adjacent cross points is reversed; the line goes up and passes through, and the line goes down and overlaps; in this step, all cross points are guaranteed to be on the upper right and hook points are guaranteed to be on the lower right, until weaving to the main body (16.01).

[0009] Step 4: Starting from line 1 (01, 01), begin weaving in reverse according to period T=3, ending at (11.S1). The developing ring is woven to the end of the support at the marked position.

[0010] Step 5: Starting from the starting point (16, 34) of line 2, weave in reverse according to the period T=3, and the ending position is (06.E3). Weave according to the weaving method of line 1.

[0011] Step 6: Begin weaving the secondary yarn from (16, S1) to (08, E3);

[0012] Step 7: Start weaving the secondary yarn from (08, S1) with yarn 4 and end at (16, E3);

[0013] Step 8: Tie the main wire and auxiliary wire ends together to form a support.

[0014] The stent of this invention still uses a Cross+Hook weaving method, employing a downward spiral weaving technique, and has only one row of Cross points between two rows of Hook points, whereas commercially available stents have two rows of Cross points between two rows of Hook points. The stent of this invention has good compliance and bending performance, making it more adaptable to the digestive system.

[0015] For hooks or crosses, the top right line is used as the reference. If the line is above, the hook or cross direction is upward; if the line is below, it's downward. For example... Figure 10 .

[0016] Furthermore, the first, second, third, and fourth filaments are made of modified nickel-titanium shape memory alloy.

[0017] Furthermore, the preparation method of the modified nickel-titanium shape memory alloy is as follows:

[0018] (1) The nickel-titanium shape memory alloy was washed once with acetone and water, then soaked in 2-3 mol / L sodium hydroxide aqueous solution at 80-90℃ for 50-60 min, and washed with water until neutral; then soaked in calcium phosphate solution at 10-15℃ for 12-20 h, and then soaked at 20-25℃ for 5-10 h; after taking it out, it was dried at room temperature to obtain a nickel-titanium shape memory alloy with a microcrystalline layer.

[0019] (2) Immerse the nickel-titanium shape memory alloy coated with microcrystalline layer in composite coating for 10-15 min, and then place it in an oven at 80-90℃ for 7-9 h to obtain modified nickel-titanium shape memory alloy.

[0020] In existing technologies, an alumina coating is typically formed on the surface of nickel-titanium shape memory alloys (NTiM alloys) to alter their surface structure. However, during research and development, it was found that the addition of the alumina coating changes the surface properties of the NTiM alloy, affecting its temperature range for shape memory effect, recovery force, etc., thus adversely impacting its functionality and applications. This invention attempts to improve the performance of the scaffold by combining materials and a special weaving method, specifically by modifying the NTiM alloy to achieve this improvement. This invention first coats the NTiM alloy surface with a thin film of calcium phosphate crystals, and then applies a composite coating. The microcrystalline layer of this invention is uniformly distributed, and the composite coating has high compatibility with it. Through synergistic effects, the mechanical stability and thermal insulation performance of the NTiM alloy are improved. Since the scaffold inserted into the esophagus comes into contact with human tissue, its materials must have good biocompatibility and not cause allergic, rejection, or toxic reactions. This invention improves the biocompatibility of the scaffold by modifying the NTiM alloy.

[0021] The nickel-titanium shape memory alloy was purchased from Furukawa Electric Machinery Co., Ltd. in Japan, with two wire diameters: 0.22mm and 0.2mm.

[0022] Furthermore, the calcium phosphate solution contains 1.6 mmol / L potassium ions, 3.2 mmol / L calcium ions, 1.8 mmol / L dihydrogen phosphate ions, and 6.2 mmol / L nitrate ions.

[0023] Furthermore, the thickness of the microcrystalline layer is 10-16 μm.

[0024] Furthermore, the preparation method of the composite coating is as follows: by weight, add 0.1-0.2 parts of nano-silver particles, 10-14 parts of polymer and 0.2-0.3 parts of polyvinylpyrrolidone to every 100 mL of dichloromethane, stir in an ice bath for 2 hours, and protect from light.

[0025] The polyvinylpyrrolidone had an average molar mass of 40,000 and was purchased from Aladdin.

[0026] Furthermore, the polymer comprises polylactic acid, polycaprolactone, and chitosan in a mass ratio of 1-3:1:0.1-0.5.

[0027] Furthermore, the silver nanoparticles have a particle size of 20 nm and a purity of 99.99%. They were purchased from Guangzhou Hongwu Materials Technology Co., Ltd.

[0028] Furthermore, the polylactic acid has a molecular weight of 40,000 and was purchased from Aladdin; the polycaprolactone has a molecular weight of 30,000 and was purchased from Sichuan Zhuoxin Biomaterials Research Co., Ltd.; and the chitosan has a molecular weight of 50,000-190,000 Da and was purchased from Aladdin.

[0029] The composite coating of this invention uses raw materials with specific components, ensuring good bonding with the microcrystalline layer. This reduces crack formation in shape memory alloy wires, improves fatigue life, and effectively prevents nickel ion release, thus reducing the potential harm of nickel ions to the body due to their biotoxicity. Adding polyvinylpyrrolidone (PVP) helps improve the dispersibility of nano-silver and the viscosity of the coating; however, excessive PPVP weakens the material's mechanical properties and reduces its thermal stability. This invention uses a polymer obtained by adding polylactic acid (PLA), polycaprolactone (PVC), and chitosan, which improves the viscosity of the composite coating and simultaneously aids in the dispersibility of nano-silver, ensuring antibacterial properties. The esophageal stent needs to adapt to the bending and peristaltic movements of the esophagus; therefore, the stent material should possess a certain degree of flexibility and plasticity, maintaining stability and continuous deformation at various positions and angles. The inventors unexpectedly discovered that when the mass ratio of polylactic acid, polycaprolactone, and chitosan is 1-3:1:0.1-0.5, the shape memory effect of nickel-titanium shape memory alloy is improved, which enhances the esophageal stent's strength and durability within the esophagus while maintaining long-term stability and functionality.

[0030] The present invention also provides a support structure obtained by the aforementioned weaving method.

[0031] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0032] 1. This invention provides a bracing method and a bracing woven using this method, which improves the existing bracing method by adopting a spiral downward bracing method with only one row of cross points between two rows of hook points, resulting in better bending performance of the bracing.

[0033] 2. The stent of this invention still adopts a Cross+Hook weaving method, using a downward spiral weaving technique, and there is only one row of Cross points between two rows of Hook points, while commercially available stents have two rows of Cross points between two rows of Hook points. The stent of this invention has good compliance and bending performance, and is better suited to the digestive system.

[0034] 3. The present invention first coats the surface of the nickel-titanium shape memory alloy with a calcium phosphate crystal film, and then coats it with a composite coating. The microcrystalline layer of the present invention is uniformly distributed, and the composite coating has high compatibility with it. Through synergistic effect, the mechanical stability and heat insulation effect of the nickel-titanium shape memory alloy are improved.

[0035] 4. The composite coating of the present invention uses raw materials with specific components, which makes it well bonded with the microcrystalline layer. This can reduce the cracking of shape memory alloy wires, improve fatigue life, and effectively prevent the release of nickel ions, thus reducing the potential harm of nickel ions to the body due to their biological toxicity.

[0036] 5. This invention, by adding polylactic acid, polycaprolactone, and chitosan to obtain a polymer, can improve the viscosity of the composite coating and simultaneously improve the dispersibility of nano-silver, ensuring antibacterial properties. The inventors also unexpectedly discovered that when the mass ratio of polylactic acid, polycaprolactone, and chitosan is 1-3:1:0.1-0.5, the shape memory effect of the nickel-titanium shape memory alloy is enhanced. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of a commercially available bracket;

[0038] Figure 2 A schematic diagram of the bending of a commercially available bracket;

[0039] Figure 3 This is a schematic diagram of the actual support structure of the present invention;

[0040] Figure 4 This is a schematic diagram of the actual bending of the bracket of the present invention;

[0041] Figure 5 This is a schematic diagram of the pin structure;

[0042] Figure 6 This is a schematic diagram of the wiring for line 1;

[0043] Figure 7 This is a schematic diagram of the routing for line 2;

[0044] Figure 8 This is a diagram illustrating the tip weaving technique; the principle is that the stacking order of adjacent cross points is reversed, and the hook points are all at the lower right; the two ends of the support are woven from the top of the main body upwards (e.g., Figure 8 The lower end is woven downwards in the same way as the upper end.

[0045] Figure 9 A schematic diagram showing the completed braiding of the support structure;

[0046] Figure 10 This is a schematic diagram of the support structure;

[0047] Figure 11 This is a diagram illustrating a Hook or Cross.

[0048] Among them, 1. Line 1; 2. Line 2; 3. Line 3; 4. Line 4; 5. Development ring; 6. Ending; 7. Cross point; 8. Hook point; 9. Entanglement. Detailed Implementation

[0049] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] Example 1

[0051] See Figure 3-4 A method for weaving a support frame, the method comprising the following steps:

[0052] Step 1: On the cylindrical fixture, install detachable cylindrical pins, evenly distributed at appropriate positions along the circumference and length; use two wires for braiding, wire 1 (1) braids half of the bracket, and wire 2 (2) braids the other half of the bracket. Wires 1 (1) and 2 (2) are the main wires used for braiding the bracket, and wires 3 (3) and 4 (4) are the auxiliary wires for braiding the bracket; install the braiding fixture and insert the pins at the corresponding positions on the fixture. See Appendix for details. Figure 5 In the diagram of this embodiment, line 1 is red, line 2 is yellow, line 3 is green, and line 4 is blue.

[0053] Step 2: Line 1 (1) Leave 1600mm for the rear braiding head end, start braiding from the main body end starting point (01.01) until braiding to the main body end (01.34). The developing ring is braided to the middle section of the support at the marked position. See details. Figure 6 .

[0054] Step 3: Leave 1600mm for the other end of line 2 (2). Start weaving from the starting point (16.34) of the main body, following these principles: the overlapping order of adjacent cross points is reversed; the line goes upwards and passes through, and downwards and presses down; in this step, all cross points are guaranteed to be on the upper right and hook points are guaranteed to be on the lower right, until weaving reaches the main body end (16.01); see details Figure 7 .

[0055] Step 4: Starting from line 1 (1) at point (01, 01), begin reverse weaving according to period T=3, ending at (11.S1). The developing ring (5) is woven to the head of the support at the marked position. See details. Figure 8 .

[0056] Step 5: Starting from line 2 (2) at point (16, 34), begin weaving in reverse according to period T=3, ending at (06.E3). Refer to the weaving method of line 1 (1) for details. Figure 8 .

[0057] Step 6: Begin weaving the secondary yarn from (16, S1) to (08, E3) for thread 3 (3). See details. Figure 9 .

[0058] Step 7: Begin weaving the secondary yarn from (08, S1) with yarn 4 (4) and end at (16, E3). See details. Figure 9 .

[0059] Step 8: Tie the main wire and auxiliary wire ends together to form a support.

[0060] The new stent still uses a Cross+Hook weaving method, employing a downward spiral weaving technique, with only one row of Cross points between two rows of Hook points, whereas commercially available stents have two rows of Cross points between two rows of Hook points. The stent of this invention has good compliance and bending performance, making it more adaptable to the digestive system.

[0061] like Figure 11 As shown, for Hooks or Crosses, the upper right line is used as the reference. If the line is above, the direction of the Hook or Cross is upward; if the line is below, it is downward. Crosses must be alternately interwoven and superimposed, see... Figure 11 As shown in the right image, when the Hook repeats its routing, it loops twice before entering the next layer of routing. Pay attention to the overlapping direction at the Hook level; it enters from below and exits from above. Figure 11 Left image.

[0062] The first, second, third, and fourth filaments are made of modified nickel-titanium shape memory alloy. The preparation method of the modified nickel-titanium shape memory alloy is as follows:

[0063] (1) The nickel-titanium shape memory alloy was washed once with acetone and water, then soaked in 2.5 mol / L sodium hydroxide aqueous solution at 85°C for 55 min, and washed with water until neutral; then soaked in calcium phosphate solution at 12°C for 15 h, and then soaked at 22°C for 6 h; after taking it out, it was dried at room temperature to obtain a nickel-titanium shape memory alloy with a microcrystalline layer.

[0064] (2) The nickel-titanium shape memory alloy coated with microcrystalline layer was immersed in the composite coating for 12 min, and then placed in an oven at 85℃ for 6 h to obtain the modified nickel-titanium shape memory alloy.

[0065] The calcium phosphate solution contained potassium ion concentrations of 1.6 mmol / L, calcium ion concentrations of 3.2 mmol / L, dihydrogen phosphate ion concentrations of 1.8 mmol / L, and nitrate ion concentrations of 6.2 mmol / L.

[0066] The thickness of the microcrystalline layer is 14 μm.

[0067] Furthermore, the preparation method of the composite coating is as follows: by weight, add 0.15 parts of nano-silver particles, 13 parts of polymer and 0.22 parts of polyvinylpyrrolidone (average molar mass 40000) to every 100 mL of dichloromethane, stir in an ice bath for 2 hours, and protect from light.

[0068] The polymer comprises polylactic acid, polycaprolactone, and chitosan in a mass ratio of 2:1:0.3.

[0069] The nano-silver particles have a particle size of 20 nm and a purity of 99.99%. The polylactic acid has a molecular weight (Mn) of 40,000; the polycaprolactone has a molecular weight (Mw) of 30,000; and the chitosan has a molecular weight of 50,000-190,000 Da.

[0070] Comparative Example 1

[0071] The difference between this comparative example and Example 1 is that the polymer comprises polylactic acid, polycaprolactone, and chitosan in a mass ratio of 1:1:1.

[0072] Comparative Example 2

[0073] The difference between this comparative example and Example 1 is that the concentrations of potassium ions in the calcium phosphate solution are 1.5 mmol / L, calcium ions are 2.5 mmol / L, dihydrogen phosphate ions are 1.5 mmol / L, and nitrate ions are 5 mmol / L. The thickness of the microcrystalline layer is 5 μm.

[0074] Comparative Example 3

[0075] Commercially available unmodified nickel-titanium shape memory alloy.

[0076] Performance testing

[0077] 1. Temperature Resistance Test: The raw materials for the composite coating were prepared into circular films with a diameter of Φ10*0.3 using a casting method. The films were placed in a constant temperature water bath at 50℃ for 0s and 40s. The surface temperature changes were recorded using a thermal imager.

[0078] 2. Antibacterial Properties: The raw material for the composite coating is poured into a mold and placed in a drying oven at 100℃ for 6 hours to obtain a completely dried film, which is then placed on a microplate. Gram-positive Staphylococcus aureus is diluted to 10⁻⁶ in LB broth. 7 The bacterial solution was diluted to CFU / ml, and 400 μL of the diluted solution was added to a well plate containing a membrane and incubated at 37°C. The inhibition rate after 4 hours was calculated as (AB) / A × 100%; where A is the OD value of the blank control and B is the OD value of the sample.

[0079] 3. Fatigue test: The strain amplitude is 4%, the load is 450MPa, and the test frequency is 1Hz. The recoverable strain at 300MPa is also tested.

[0080] Table 1 Measurement Results

[0081]

[0082] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles 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 method for weaving a support frame, characterized in that, The weaving method includes the following steps: Step 1: On the cylindrical fixture, install detachable cylindrical pins, evenly distributed at appropriate positions along the circumference and length; use two wires for braiding, the first wire braids half of the bracket, and the second wire braids the other half of the bracket, the first and second wires are the main wires, and the third and fourth wires are the auxiliary wires; install the braiding fixture and insert the pins at the corresponding positions on the fixture; Step 2: Leave 1600mm for the first filament before weaving the head end. Start weaving from the main body end starting point A (01.01) until weaving to the main body end A (01.34). The developing ring is woven to the middle section of the support at the marked position. Step 3: Leave 1600mm of the second filament before weaving the other end. Start weaving from the main body end starting point B (16.34) and follow these principles: the overlapping order of adjacent cross points is reversed; the thread goes up and passes through, and the thread goes down and presses down; in this step, all cross points are guaranteed to be on the upper right and hook points are guaranteed to be on the lower right, until weaving to the main body end B (16.01). Step 4: Starting from the first filament point A (01, 01), weave in reverse according to the period T=3, with the end point being (11.S1). The developing ring is woven to the head of the support at the marked position. Step 5: Starting from the second filament at point C(16, 34), begin weaving in reverse with a period of T=3, ending at (06, E3), following the weaving method of the first filament; Step 6: The third filament begins to weave the secondary filament from (16, S1) and ends at (08, E3); Step 7: The fourth filament begins to weave the secondary filament from (08, S1) and ends at (16, E3); Step 8: Tie the main wire and auxiliary wire ends together to form a support structure; The first, second, third, and fourth wires are made of modified nickel-titanium shape memory alloy. The modified nickel-titanium shape memory alloy is prepared by immersing the nickel-titanium shape memory alloy coated with a microcrystalline layer in a composite coating for 10-15 minutes, and then placing it in an oven at 80-90℃ for 7-9 hours to obtain the modified nickel-titanium shape memory alloy. The composite coating is prepared by adding 0.1-0.2 parts by weight of nano-silver particles, 10-14 parts by weight of polymer and 0.2-0.3 parts by weight of polyvinylpyrrolidone to 100 mL of dichloromethane, stirring in an ice bath for 2 hours, and protecting from light. The polymer comprises polylactic acid, polycaprolactone, and chitosan in a mass ratio of 1-3:1:0.1-0.

5.

2. The bracing method according to claim 1, characterized in that, The preparation method of the nickel-titanium shape memory alloy with microcrystalline layer is as follows: the nickel-titanium shape memory alloy is washed once with acetone and water, then soaked in 2-3 mol / L sodium hydroxide aqueous solution at 80-90℃ for 50-60 min, and washed with water until neutral; then soaked in calcium phosphate solution at 10-15℃ for 12-20 h, and then soaked at 20-25℃ for 5-10 h; after removal, it is dried at room temperature to obtain the nickel-titanium shape memory alloy with microcrystalline layer.

3. The bracing method according to claim 2, characterized in that, The calcium phosphate solution contained potassium ion concentrations of 1.6 mmol / L, calcium ion concentrations of 3.2 mmol / L, dihydrogen phosphate ion concentrations of 1.8 mmol / L, and nitrate ion concentrations of 6.2 mmol / L.

4. The bracing method according to claim 3, characterized in that, The thickness of the microcrystalline layer is 10-16 μm.

5. The bracing method according to claim 1, characterized in that, The nano-silver particles have a particle size of 20 nm and a purity of 99.99%.

6. The bracing method according to claim 1, characterized in that, The polylactic acid has a molecular weight of 40,000 (Mn); the polycaprolactone has a molecular weight of 30,000 (Mw); and the chitosan has a molecular weight of 50,000-190,000 (Da).

7. The stent obtained by the stent weaving method according to any one of claims 1-6.

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