A method for preparing a needle-free electrostatically spun starch 2D nanofiber composite film and 3D nanofiber sponge at room temperature

Abstract

This invention discloses a room-temperature preparation method for needle-free electrospun starch 2D nanofiber composite membranes and 3D nanofiber sponges. By preparing a starch / sodium hydroxide composite solution and employing electrospinning, 2D starch nanofiber composite membranes containing sodium hydroxide and 3D nanofiber sponges are obtained. The composite membranes prepared by this invention have a simple preparation method, uniform nanofiber diameter, controllable thickness, do not require other crosslinking agents, and have low production costs, showing potential application value in bioengineering, tissue engineering, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of natural biopolymer material processing and relates to a method for preparing starch nanofibers by electrospinning. Background Technology

[0002] Starch is a natural polymer compound that is abundant and inexpensive, possessing advantages such as being renewable, immunogenic, biodegradable, and commercially viable. Natural starch typically lacks thermoplasticity; when heated, it undergoes thermal degradation before reaching its crystallization melting point, thus making it impossible to directly melt and process natural starch into fibers.

[0003] Electrospinning is an effective method for preparing starch into fibers. Research on the application of natural starch in electrospinning began in 2012, when American scientists Ziegler et al. reported the preparation of starch fibers by "wet" electrospinning using dimethyl sulfoxide as a solvent and ethanol as a coagulation bath precipitant (Kong & Ziegler, Biomacromolecules, 2012, 13(8): 2247-2253). In 2015, Lancuski et al. first reported "dry" electrospinning using formic acid as a solvent, which could obtain starch nanofibers with diameters of 80-300 nm (Lancuski et al., Biomacromolecules, 2015, 16(8): 2529-2536). Both "wet" and "dry" electrospinning processes require a large amount of organic solvent (dimethyl sulfoxide or formic acid) to dissolve starch, posing safety hazards and limiting their application in the food, pharmaceutical, and cosmetic fields.

[0004] Chinese invention patent (2021112539291) discloses a method for preparing starch nanofibers using water as the sole solvent and without the use of organic solvents. This method uses a debranched solution of high amylose as raw material, which is sheared and homogenized to form a spinning solution, and then electrospinned to obtain starch nanofibers. This method is complex, requiring high-temperature, high-pressure gelatinization and spinning at the gelatinization temperature. If the temperature decreases, the starch ages, affecting the electrospinning effect. Summary of the Invention

[0005] To address the shortcomings of existing technologies where the strong hydrogen bonding of starch makes it difficult to electrospin alone and requires modification, this invention provides a simple method for preparing 2D and 3D starch nanofiber membranes and sponges at room temperature using electrospinning. This method utilizes electrospinning to prepare edible films from pure starch. Based on room temperature and pressure conditions, it lowers the starch gelatinization temperature, accelerating gelatinization and preparing nanofibers. The starch nanofiber membranes possess certain mechanical properties. By electrospinning starch fibers, further processing can yield textile products such as nonwoven fabrics or textiles of various forms, showing great application potential in pharmaceutical fields such as drug delivery, wound dressings, and tissue engineering. This method is simple, rapid, non-toxic, and harmless, requiring no large-scale equipment. The prepared fiber membranes are easy to handle, the raw materials are readily available, and mass production is easily achieved.

[0006] A method for preparing starch 2D nanofiber composite membranes or 3D nanofiber sponges at room temperature via needle-free electrospinning, the method comprising the following steps:

[0007] (1) Dissolve sodium hydroxide in deionized water to prepare a 3wt% to 5wt% solution, and stir until the sodium hydroxide is completely dissolved to obtain a sodium hydroxide solution;

[0008] (2) Dissolve starch directly in sodium hydroxide solution and stir until the starch is completely gelatinized to obtain a gelatinized starch solution;

[0009] (3) Place the starch solution obtained in step (2) on an electrospinning device for electrospinning to obtain a starch 2D nanofiber composite film or 3D nanofiber sponge with uniform thickness containing sodium hydroxide.

[0010] (4) Soak the starch 2D nanofiber composite membrane or 3D nanofiber sponge containing sodium hydroxide obtained in step (3) in acetic acid.

[0011] (5) Take out the starch 2D nanofiber composite membrane or 3D nanofiber sponge containing sodium hydroxide soaked in acetic acid in step (4), put it in a vacuum drying oven to dry, and you can get pure starch 2D nanofiber composite membrane or 3D nanofiber sponge.

[0012] As a preferred technical solution, in step (1), the concentration of the sodium hydroxide solution is 3wt% to 5wt%.

[0013] As a preferred technical solution, in step (2), the concentration of starch in the sodium hydroxide solution is 14wt% to 16wt%, and the stirring time is 6-8h.

[0014] As a preferred technical solution, in step (3), the conditions for spinning by the needleless electrospinning equipment are: voltage 60-80kV, solution box speed 20-60mm / s, receiving distance 180mm-220mm, and spinning time 4-5h.

[0015] As a preferred technical solution, in step (3), the humidity of the spinning is 40-45%.

[0016] As a preferred technical solution, when the concentration of sodium hydroxide solution is 3wt% to 4wt% and the concentration of starch in sodium hydroxide solution is 14wt% to 16wt%, a 2D nanofiber composite membrane containing sodium hydroxide can be obtained.

[0017] As a preferred technical solution, when the concentration of sodium hydroxide solution is 5 wt% and the concentration of starch in sodium hydroxide solution is 14 wt% to 16 wt%, a starch 3D nanofiber sponge containing sodium hydroxide can be obtained.

[0018] As a preferred technical solution, in step (4), the soaking time is 5-10 minutes.

[0019] As a preferred technical solution, in step (5), the drying temperature is 40-50℃ and the drying time is 6-8h.

[0020] As a preferred technical solution, the starch is high amylose starch, with an amylose content greater than or equal to 70%.

[0021] As a preferred technical solution, the starch is corn starch.

[0022] The theoretical basis for determining the process flow of this invention is:

[0023] (1) Adding an appropriate amount of sodium hydroxide to starch can promote gelatinization. Sodium hydroxide combines with the hydroxyl groups in starch, breaks hydrogen bonds, weakens the interaction forces between macromolecules, and lowers the gelatinization temperature.

[0024] (2) Sodium hydroxide is a strong base, and acetic acid is a weak acid; acid-base neutralization occurs. The reaction equation for sodium hydroxide and acetic acid is: CH3COO + NaOH = CH3COONa + H2O.

[0025] The beneficial effects of this invention are:

[0026] 1. The process is simple and can be carried out at room temperature.

[0027] 2. Sodium hydroxide has antiseptic properties. The sodium hydroxide-containing nanofiber membrane prepared by this invention without acid soaking can be used as a food preservation film to extend the shelf life.

[0028] 3. This invention can prepare pure starch nanofiber membranes, which are processed on needleless electrospinning equipment. Needleless electrospinning has high processing efficiency and can be industrialized.

[0029] 4. The pure nanofiber membrane prepared by the present invention has uniform diameter and uniform thickness, which is controllable.

[0030] 5. The pure nanofiber membrane prepared by this invention does not use crosslinking agents such as pentylene glycol and has certain mechanical properties.

[0031] 6. 3D nanofiber sponges can be prepared by adjusting the process.

[0032] 7. Low production cost, with potential applications in bioengineering, tissue engineering, and other fields. Attached Figure Description

[0033] Figure 1 This is a schematic diagram illustrating the principle of needleless electrospinning.

[0034] Needleless electrospinning is a spinning method that utilizes a high-voltage electric field to directly create a jet stream on the surface of a free liquid. The spinning solution in the solution chamber moves back and forth on the electrode wires. Under the high-voltage electric field, a jet stream is directly formed on the free liquid surface of the electrode wires, and the fibers are spun.

[0035] Figure 2 The needle-free electrospun starch nanofiber membrane obtained in Example 1;

[0036] Figure 3 The images show SEM comparisons of the needle-free electrospun starch nanofiber membrane obtained in Example 1 before and after acetic acid immersion; where (a) is before immersion and (b) is after immersion.

[0037] Figure 4 The needle-free electrospun starch nanofiber membrane obtained in Example 2;

[0038] Figure 5 The images show SEM comparisons of the needle-free electrospun starch nanofiber membrane obtained in Example 2 before and after acetic acid immersion; where (a) is before immersion and (b) is after immersion.

[0039] Figure 6 The needle-free electrospun starch nanofiber membrane obtained in Example 3;

[0040] Figure 7 The images show SEM comparisons of the needle-free electrospun starch nanofiber membrane obtained in Example 3 before and after acetic acid immersion; where (a) is before immersion and (b) is after immersion.

[0041] Figure 8 The needle-free electrospun starch nanofiber membrane obtained in Example 4;

[0042] Figure 9 The images show SEM comparisons of the needle-free electrospun starch nanofiber membrane obtained in Example 4 before and after acetic acid immersion; where (a) is before immersion and (b) is after immersion. Detailed Implementation

[0043] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the invention, but do not limit the invention in any way.

[0044] The following embodiments of the present invention include testing methods and equipment:

[0045] The following materials are selected in the embodiments of the present invention:

[0046] High amylose content: corn starch, amylose content 70%; sodium hydroxide; acetic acid;

[0047] Scanning electron microscope (SEM): JSM-780DF ultra-high resolution thermal field emission scanning electron microscope, JEDL, Japan Electron.

[0048] Needleless electrospinning equipment: Nano spider silk electrospinning machine, ELMARCO (Czech Republic);

[0049] Drying equipment: DZF-6020 electric thermostatic drying oven, Shanghai Jinghong Medical Instrument Co., Ltd.;

[0050] Thickness testing equipment: YG141LA digital fabric thickness gauge, Laizhou Electronic Instruments Co., Ltd.

[0051] Example 1

[0052] Sodium hydroxide was directly dissolved in deionized water to prepare a 3 wt% solution, which was then stirred at room temperature until the solution became clear. High-amylose starch was directly dissolved in the 3 wt% sodium hydroxide solution to prepare a 15 wt% solution, which was then stirred at room temperature until the starch was completely gelatinized, yielding a starch / sodium hydroxide solution (starch film). Needleless electrospinning was carried out at room temperature and 40% humidity. The starch / sodium hydroxide solution was placed in the needleless electrospinning film... Figure 1 As shown, on both sides of the solution box, with a spinning voltage of 60KV, a solution box speed of 20mm / s, a receiving distance of 180mm, and a spinning time of 5h, a starch electrospun nanofiber membrane with uniform thickness of 0.243mm and a tensile strength of 0.01MPa can be obtained. The starch membrane is as follows... Figure 2 As shown, SEM Figure 3 As shown in (a), the nanofibers have a uniform diameter distribution with an average diameter of 908 nm. The starch membrane was immersed in acetic acid for 10 min, then removed and placed in a vacuum drying oven at 50 °C for 6 h. The SEM images of the dried starch membrane are shown below. Figure 3As shown in (b), the nanofibers have a smooth surface, are tightly packed, and have an average diameter of 251 nm.

[0053] Example 2

[0054] Sodium hydroxide was directly dissolved in deionized water to prepare a 4 wt% solution, which was then stirred at room temperature until the solution became clear. High-amylose starch was directly dissolved in the 4 wt% sodium hydroxide solution to prepare a 15 wt% solution, which was then stirred at room temperature until the starch was completely gelatinized, yielding a starch / sodium hydroxide solution. Needleless electrospinning was carried out at room temperature and 40% humidity. The starch / sodium hydroxide solution was placed in the needleless electrospinning... Figure 1 As shown, on both sides of the solution box, with a spinning voltage of 70KV, a solution box speed of 40mm / s, a receiving distance of 200mm, and a spinning time of 5h, a starch electrospun nanofiber membrane (starch membrane) of uniform thickness can be obtained, with a thickness of 0.366mm and a tensile strength of 0.02MPa. The starch membrane is as follows... Figure 4 As shown, SEM Figure 5 As shown in (a), the nanofibers have a uniform diameter distribution with an average diameter of 423 nm. The starch membrane was immersed in acetic acid for 10 min, then removed and placed in a vacuum drying oven at 50 °C for 6 h. The SEM images of the dried starch membrane are shown below. Figure 5 As shown in (b), the nanofibers have a smooth surface, are tightly packed, and have an average diameter of 298 nm.

[0055] Example 3

[0056] Sodium hydroxide was directly dissolved in deionized water to prepare a 5 wt% solution, which was then stirred at room temperature until the solution became clear. High-amylose starch was directly dissolved in the 5 wt% sodium hydroxide solution to prepare a 14 wt% solution, which was then stirred at room temperature until the starch was completely gelatinized, yielding a starch / sodium hydroxide solution. Needleless electrospinning was carried out at room temperature and 40% humidity. The starch / sodium hydroxide solution was placed in the needleless electrospinning... Figure 1 As shown, on both sides of the solution box, with a spinning voltage of 80KV, a solution box speed of 60mm / s, a receiving distance of 220mm, and a spinning time of 4h, a starch electrospun nanofiber membrane (starch membrane) of uniform thickness can be obtained, with a thickness of 0.447mm and a tensile strength of 0.13MPa. The starch membrane is as follows... Figure 6 As shown, SEM Figure 7 As shown in (a), the nanofibers have a uniform diameter distribution with an average diameter of 514 nm. The starch membrane was immersed in acetic acid for 10 min, then removed and placed in a vacuum drying oven at 50 °C for 6 h. The SEM images of the dried starch membrane are shown below. Figure 7 As shown in (b), the nanofibers have a smooth surface, are tightly packed, and have an average diameter of 347 nm.

[0057] Example 4

[0058] Sodium hydroxide was directly dissolved in deionized water to prepare a 5 wt% solution, which was then stirred at room temperature until the solution became clear. High-amylose starch was directly dissolved in the 5 wt% sodium hydroxide solution to prepare a 16 wt% solution, which was then stirred at room temperature until the starch was completely gelatinized, yielding a starch / sodium hydroxide solution. Needleless electrospinning was carried out at room temperature and 40% humidity. The starch / sodium hydroxide solution was placed in the needleless electrospinning... Figure 1 As shown, on both sides of the solution box, with a spinning voltage of 80KV, a solution box speed of 60mm / s, a receiving distance of 220mm, and a spinning time of 4h, a starch electrospun nanofiber membrane (starch membrane) of uniform thickness, with a thickness of 0.521mm and a tensile strength of 0.07MPa, can be obtained. The starch membrane is as follows... Figure 8 As shown, SEM Figure 9 As shown in (a), the nanofibers have a uniform diameter distribution with an average diameter of 493 nm. The starch membrane was immersed in acetic acid for 10 min, then removed and placed in a vacuum drying oven at 50 °C for 6 h. The SEM images of the dried starch membrane are shown below. Figure 9 As shown in (b), the nanofibers have a smooth surface, are tightly packed, and have an average diameter of 352 nm.

Claims

1. A method for preparing starch 2D nanofiber composite membranes or 3D nanofiber sponges at room temperature via needle-free electrospinning, characterized in that, The method includes the following steps: (1) Dissolve starch in sodium hydroxide solution and stir until the starch gelatinizes to obtain a gelatinized starch solution; (2) The gelatinized starch solution is placed on a needleless electrospinning device for electrospinning to obtain a starch 2D nanofiber composite film or 3D nanofiber sponge containing sodium hydroxide. (3) Soak the 2D nanofiber composite membrane or 3D nanofiber sponge containing sodium hydroxide in acetic acid and dry it to obtain pure starch 2D nanofiber composite membrane or 3D nanofiber sponge. The starch is high in amylose, with an amylose content greater than or equal to 70%. In step (1), the concentration of sodium hydroxide solution is 3wt% to 5wt%, the concentration of starch in sodium hydroxide solution is 14wt% to 16wt%, and the stirring time is 6-8h; In step (2), the conditions for needleless electrospinning are: voltage 60-80kV, solution box speed 20-60mm / s, and receiving distance 180mm-220mm.

2. The method according to claim 1, characterized in that, In step (2), the spinning time is 4 to 5 hours.

3. The method according to claim 1, characterized in that, In step (2), the humidity of the spinning process is 40-45%.

4. The method according to claim 1 or 2, characterized in that, When the concentration of sodium hydroxide solution is 3wt% to 4wt% and the concentration of starch in sodium hydroxide solution is 14wt% to 16wt%, a 2D nanofiber composite membrane containing sodium hydroxide can be obtained.

5. The method according to claim 1 or 2, characterized in that, When the concentration of sodium hydroxide solution is 5 wt% and the concentration of starch in sodium hydroxide solution is 14 wt% to 16 wt%, a starch 3D nanofiber sponge containing sodium hydroxide can be obtained.

6. The method according to claim 1, characterized in that, In step (3), the soaking time is 5-10 min, the drying temperature is 40-50℃, and the drying time is 6-8 h.

7. The method according to claim 1, characterized in that, The starch is corn starch.

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