Preparation and application of micron fiber degradable tissue engineering scaffold based on solution electrostatic spinning

Abstract

The invention belongs to the technical field of large-diameter micron fibers, and relates to preparation and application of a micron fiber degradable tissue engineering scaffold based on solution electrostatic spinning, during preparation, a degradable polymer is dissolved in a solvent to prepare a spinning solution, and electrostatic spinning is adopted to prepare the micron fiber degradable tissue engineering scaffold; the viscosity of the spinning solution is 3-6 Pa.s; the boiling point of the solvent is 38-70 DEG C, or the vapor pressure is 100-300 mmHg; the dielectric constant of the solvent is 4-12F / m; the spinning temperature is 2-8 DEG C lower than the boiling point of the solvent and 20 DEG C higher than the melting point of the degradable polymer; the diameter of the fiber in the micron fiber degradable tissue engineering scaffold is more than 15 microns; the composite material can be used as a wound dressing, a tendon patch, a pelvic floor patch, a hernia patch, a periodontal patch, a dura mater patch and other tissue repair materials. The method provided by the invention can be used for preparing the fiber with the diameter of more than 15 microns, and meanwhile, the forming defect caused by fiber adhesion and solvent residue is avoided; the application range is wide.

Description

Technical Field

[0001] This invention belongs to the field of large-diameter microfiber technology, and relates to the preparation and application of a microfiber biodegradable tissue engineering scaffold based on solution electrospinning. Background Technology

[0002] With the increasing demand for tissue engineering scaffolds, the fabrication technology of micron-scale fiber scaffolds and its limitations in fiber diameter control, spatial structure morphology, and molding efficiency have become one of the core issues of current research. Currently, there are three main methods for preparing micron-scale fibers: gel spinning, melt electrospinning, and solution electrospinning.

[0003] Gel spinning technology: This technology can continuously produce micron fiber materials with a diameter ≥10μm, but the obtained fibers are in the form of monofilaments and cannot form fiber assemblies.

[0004] Melt electrospinning (electrostatic direct writing) technology: High-temperature heating melts polymer particles into polymer melt. Based on a 3D printer, a positive high voltage power supply (3kV~8kV) is added to the printing needle. The positive voltage causes the melt extruded from the needle to form a Taylor cone, which stretches the fiber to form a fiber with a diameter ≥15μm. The scaffold is formed according to the printing path designed by 3D modeling. However, it is difficult for the fiber assembly to form a three-dimensional stacked structure.

[0005] Melt electrospinning technology uses polymer melt instead of solution as the jet medium, which can effectively avoid the problem of insufficient solvent evaporation. It can usually obtain large-diameter micron fibers with controllable diameter and uniform morphology, which is a major advantage of this technology. However, in the melt electrospinning process, the fiber deposition path needs to be pre-planned, and it can only be printed and laid out one by one along the preset path. If a randomly distributed fiber network structure is required, the following method can usually be used: first print a layer of parallel fibers, then rotate the printing path by a small angle relative to the previous layer to print the second layer of fibers, and then continue to increase the rotation angle layer by layer to repeat the printing, and finally form an approximately random scaffold structure on a macroscopic scale, for example, in the literature (3DPrinted Mesh Geometry Modulates Immune Response and Interface Biology in Mouse and Sheep Model: Implications for Pelvic Floor Surgery[J]. Adv. Mater.2024, 12(11), 2405004). While this method can construct near-random microfiber scaffolds to some extent, it has significant drawbacks: First, the printing process is highly dependent on path planning, requiring precise control layer by layer and fiber by fiber, resulting in complex path design; second, it has low molding efficiency and is time-consuming, which is not conducive to the rapid construction of large-size or thick-walled microfiber scaffolds. Therefore, although existing melt electrospinning technology has advantages in terms of controllable fiber diameter and uniform morphology, it still faces technical bottlenecks such as complex processes and low efficiency in the rapid construction of large-size, randomly distributed microfiber structures.

[0006] Solution electrospinning: Solution electrospinning is the mainstream method for preparing three-dimensional stacked, randomly distributed fiber network structures. Polymers are dissolved in organic solvents to form a melt. Then, by adjusting the spinning parameters such as electrospinning process parameters (increasing solution concentration, increasing injection speed, reducing voltage, etc.) and environmental parameters (temperature and humidity, etc.), the solvent evaporates and deposits on the receiving platform to form a three-dimensional stacked fiber aggregate structure. Fiber materials with diameters between 50 nm and 10 μm can be formed and randomly deposited on the collector. However, this technology has a long-standing inherent bottleneck: the prepared fiber size is small. Currently, no solution electrospinned fibers with diameters greater than 10 μm have been found. This is because when the solution concentration and injection speed are further increased and the voltage is further reduced to obtain fibers with diameters greater than 10 μm, a series of problems will occur: (1) The fibers on the receiving platform are severely adhered, the fiber morphology is not smooth and uneven, and they may even be unable to form fibers, resulting in a significant deterioration in the forming effect of fibers with diameters greater than 10 μm. (2) The solution is too viscous to be mixed evenly, and it is difficult to extrude and stretch, making it difficult to produce stable fibers.

[0007] This is mainly because in conventional solution electrospinning experiments, the inner diameter of the commonly used stainless steel needle is approximately 0.2~1.5 mm. Due to the formation of the Taylor cone, the jet diameter will be much smaller than the needle aperture. Under the influence of the charged component, the jet forms a ring structure and becomes significantly thinner, ultimately forming submicron fibers. If the target fiber diameter in solution electrospinning is increased to >10 μm, it can be seen through conventional electrospinning parameter control methods that the fiber diameter is the result of the synergistic effect of multiple factors such as electric field force, charge repulsion, and surface tension. Munawar et al. established a mathematical model based on experimental data, giving the relationship between fiber diameter and parameters in electrospinning:

[0008] ;

[0009] Where c is the concentration, η is the viscosity, Q is the flow rate, X is the collection distance, U is the voltage, ω is the rotational speed, and I is the current.

[0010] According to this formula, theoretically, to increase the fiber diameter, one could try increasing the solution viscosity, concentration, or flow rate. However, the adjustable range of these parameters is limited by the system stability and fiber formation mechanism: excessively high viscosity and concentration can lead to difficulties in jet formation, resulting in the inability to form continuous fibers or uneven fiber morphology; excessively high flow rates can cause insufficient solvent evaporation, causing the fibers to collapse and stick together before collection. It also faces the dual barriers of hydrodynamic instability and mass transfer kinetics limitations. The contradiction between whiplash stretching and Rayleigh splitting: high electric field stretching tends to induce exponential refinement or splitting of the jet, making it difficult to maintain the jet stability of large-diameter monofilaments; reducing the electric field strength leads to structural collapse due to limited radial diffusion of the solvent: the specific surface area of ​​micron-sized jets is significantly reduced, and the solvent evaporation rate lags behind the phase change solidification rate, resulting in excessive residual solvent during fiber deposition. Reduced jet splitting and insufficient solvent evaporation can couple, forming defects such as adhesion, collapse, and morphological distortion. Therefore, the conventional electrospinning process mechanism determines that the fiber forming process is inevitably accompanied by continuous electrostatic repulsion and whipping instability. Even if changing the parameters can have a certain regulatory effect on the fiber diameter, this physical nature makes it difficult for traditional solution systems to break through the 10-micron diameter range.

[0011] Therefore, how to achieve rapid in-situ solidification while suppressing excessive jet stretching, and stably form micron-sized fibers with a diameter greater than 10 μm, while maintaining uniform fiber morphology and structural integrity, and avoiding forming defects caused by fiber adhesion and solvent residue, is an urgent problem to be solved. Summary of the Invention

[0012] The purpose of this invention is to address the problems existing in the prior art and provide a method for preparing and applying a microfiber biodegradable tissue engineering scaffold based on solution electrospinning. This application achieves dense, smooth, large-diameter fibers through a set of precise synergistic process parameters. Instead of simply adjusting a single process parameter, it employs a synergistic strategy of reducing filament stretching, enhancing solvent evaporation, and extending the jet residence time to form repeatable and stable process parameters. This overcomes the aforementioned technical bottlenecks to obtain a three-dimensionally stacked, large-diameter microfiber scaffold without significant adhesion.

[0013] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0014] A method for preparing micron-fiber biodegradable tissue engineering scaffolds based on solution electrospinning involves dissolving a biodegradable polymer in a solvent to prepare a spinning solution, and then using electrospinning to prepare micron-fiber biodegradable tissue engineering scaffolds.

[0015] The viscosity of the spinning solution is 3~6 Pa·s; the solution for preparing micron fibers should have a high viscosity, but if the viscosity is too high, the voltage will be unable to overcome the jet tension and fibers cannot be formed; if the viscosity is too low, the fibers will be too fine and it will be difficult to ensure that the fibers formed are micron fibers.

[0016] The solvent has a boiling point of 38~70℃ or a vapor pressure of 100~300mmHg (approximately 15~45kPa). When the vapor pressure is equal to atmospheric pressure, the lower the boiling point, the stronger the volatility. A boiling point in the range of 38~70℃ ensures timely evaporation of the solvent and avoids excessively rapid evaporation that could clog the spinning needle. Alternatively, a vapor pressure range of 100~300mmHg can also meet the requirement of rapid solvent evaporation into fibers without causing the solution to rapidly evaporate and solidify at the spinning needle, thus preventing clogging of the needle.

[0017] The dielectric constant of the solvent is 4~12 F / m. In electrospinning, it is generally believed that the higher the dielectric constant of the solvent, the higher the charge carried by the jet, the more thorough the whipping and stretching of the jet in the unstable section, and the finer the fiber. Conversely, a low dielectric constant suppresses jet splitting and whipping, resulting in a coarser fiber diameter. Therefore, a dielectric constant range of 4~12 F / m is most suitable.

[0018] The spinning temperature is 2-8°C lower than the solvent boiling point and more than 20°C lower than the melting point of the biodegradable polymer;

[0019] The microfiber biodegradable tissue engineering scaffold has a fiber diameter of more than 15μm and is a three-dimensional stacked random fiber network structure. The fibers are continuous, uniformly distributed, without obvious beading or adhesion.

[0020] As a preferred technical solution:

[0021] The method for preparing microfiber biodegradable tissue engineering scaffolds based on solution electrospinning, as described above, has a fiber diameter of 15~25μm in the microfiber biodegradable tissue engineering scaffold.

[0022] The preparation method of the microfiber biodegradable tissue engineering scaffold based on solution electrospinning as described above has a thickness of 200~1000μm, an elongation at break ≥50%, a tensile strength of 2.5~8.8MPa, and an elastic modulus of 12~25MPa.

[0023] The degradation time of microfiber biodegradable tissue engineering scaffolds is 6 to 24 months. After 3 months of degradation, the mechanical properties (tensile strength, burst strength, elongation at break and elastic modulus) of microfiber tissue engineering scaffolds remain at 50 to 80%.

[0024] As described above, the method for preparing microfiber biodegradable tissue engineering scaffolds based on solution electrospinning uses polycaprolactone, polylactic acid, polydioxanone, or polyglycolic acid as the biodegradable polymer. The number average molecular weight of the biodegradable polymer is not higher than 100,000. If the molecular weight is too large when the concentration is increased, it will be difficult to stir the solution evenly and the voltage stretching effect will be poor.

[0025] The method for preparing microfiber biodegradable tissue engineering scaffolds based on solution electrospinning, as described above, uses dichloromethane, trichloromethane, hexafluoroisopropanol, tetrahydrofuran, or acetone as the solvent.

[0026] The specific steps of the method for preparing biodegradable tissue engineering scaffolds based on solution electrospinning of micron fibers, as described above, are as follows:

[0027] (1) Prepare a spinning solution by dissolving the biodegradable polymer in a solvent;

[0028] (2) The spinning solution is loaded into the syringe and the positive high voltage electrostatic generator is connected to the spinning nozzle. The potential difference of the receiving roller grounding wire is kept at 0. In conventional processes, a negative voltage is usually applied to the receiving roller to enhance the attraction of the positively charged whip jet, thereby accelerating fiber deposition. However, in this invention, if the receiving roller is charged with a negative voltage, the jet will be deposited on the roller surface too early, shortening the jet's flight time in the air, which is not conducive to the complete evaporation of the solvent. By keeping the potential difference of the receiving roller grounding wire at 0, its attraction to the positively charged jet is weakened, and no additional stretching effect is generated on the jet. At the same time, the residence time of the jet in the air is effectively extended, providing more favorable conditions for the full evaporation of the solvent, thereby avoiding the adhesion and morphological collapse of coarse-diameter fibers during reception.

[0029] (3) Turn on the positive high voltage electrostatic generator to provide positive high voltage electrostatic for the spinning nozzle. After setting the spinning voltage, receiving distance, the angle between the radial direction of the spinning nozzle and the upper tangent of the receiving roller, and the speed of the spinning solution injection, perform electrostatic spinning and use the rotating receiving roller to receive the micron-sized fibers formed by the whip jet in the unstable section.

[0030] (4) According to the thickness requirements, obtain a microfiber biodegradable tissue engineering scaffold with continuous microfiber, uniform distribution, no obvious beading, and no obvious adhesion, and dry it in a vacuum oven at 37°C for 24 hours.

[0031] As described above, in the preparation method of microfiber biodegradable tissue engineering scaffold based on solution electrospinning, the concentration of the spinning solution in step (1) is 30~55wt%. This concentration range ensures that the polymer can be fully dissolved in the solvent and uniformly dispersed by mechanical stirring, avoiding uneven stirring or gel agglomeration due to excessively high solution viscosity. On the other hand, it provides sufficient molecular chain entanglement, enabling the jet to have good fiber-forming ability during the spinning process, thus providing the necessary conditions for obtaining coarse-diameter microfibers with a diameter of 15μm~25μm.

[0032] In the preparation method of microfiber biodegradable tissue engineering scaffold based on solution electrospinning as described above, the spinning nozzle specification in step (2) is 20G~24G.

[0033] As described above, in the preparation method of microfiber biodegradable tissue engineering scaffold based on solution electrospinning, the spinning voltage (voltage of the positive high voltage electrostatic generator) in step (3) is 8~16kV. The smaller the voltage, the slower the charge accumulation efficiency, the weaker the charge repulsion in the jet, and the weaker the stretching effect on the jet, which is conducive to forming fibers with larger diameters. However, at the same time, it is necessary to ensure a sufficiently strong electric field to continuously provide positive charges to the jet, so that the charge in the stable section of the jet can accumulate quickly and generate sufficient electrostatic repulsion, thereby inducing the jet to split at the end of the stable section and forming multiple unstable whipping jets. This can maintain a relatively large fiber diameter and improve the efficiency of solvent evaporation in the air through the dispersion distribution of multiple jets, thus improving the fiber forming quality. The receiving distance is 16~20cm. Appropriately increasing the receiving distance can provide a longer dwell path and time for the whipping jet to fly and whip in the air. In the fixed-segment jet stage, the fibers have sufficient time in the air to complete solvent evaporation and morphological shaping, thus preventing adhesion and collapse of the fibers when they are deposited on the receiving roller while still in a solution or high solvent content state. However, the receiving distance cannot be too large, as this will weaken the attraction of 0 potential to positively charged fibers, making it impossible for the whip jet to deposit on the platform. The radial angle between the spinning nozzle and the upper tangent of the receiving roller is 0°~20°, and the spinning solution injection rate is 6~10mL / h. When the solution flow rate is too low, the jet will be ejected intermittently from the nozzle, resulting in the inability to continuously stretch the jet, thus affecting the fiber diameter and morphology. As the solution flow rate increases, the volume per unit length of the jet increases, and the fiber diameter increases. This injection rate, combined with a high-concentration solution, increases the polymer content in the jet, which is beneficial for obtaining a larger fiber diameter. The spinning temperature is 35~60℃, and the spinning relative humidity is 18~30%.

[0034] The spinning temperature for a given system is determined by the melting point of the chosen polymer and the boiling point of the solvent. The listed solvent boiling points are: dichloromethane 40℃; trichloromethane 61℃; hexafluoroisopropanol 58℃; tetrahydrofuran 66℃; acetone 56℃. The listed polymer melting temperatures are: polycaprolactone 60℃; polylactic acid 180℃; polydioxanone 110℃; polyvinyl alcohol 230℃. The boiling point of the solvent should be lower than the melting point of the polymer to ensure that the fiber morphology is not affected by temperature during the high-temperature solvent evaporation process.

[0035] The biodegradable tissue-engineered scaffold prepared by the method described in any of the preceding claims may be used as a wound dressing, tendon patch, pelvic floor patch, hernia patch, periodontal patch, or dura mater patch.

[0036] Invention Mechanism:

[0037] In conventional electrospinning, the fiber diameter is primarily determined by the jet stretching during the spinning process. The jet includes a stable segment and an unstable segment. Compared to the straight and short stable segment jet, the unstable segment jet has an extremely long spiral coil motion path, and its stretching degree and duration are far greater than that of the stable segment jet. Under the influence of an electric field, the morphological changes of the charged viscous liquid at the tip of the spinning needle are related to the voltage. As the voltage increases, the charge on the droplet surface increases. When the repulsive force generated by the charge balances the surface tension of the droplet, the hemispherical droplet evolves into a balanced conical droplet. When the repulsive force exceeds the surface tension, the conical droplet ejects a fine jet; this cone is called a Taylor cone, and the stable jet formed from the bottom of the Taylor cone is called a Rayleigh jet. As the charge gradually accumulates, the same positive charges in the jet generate repulsive forces. When the repulsive force exceeds the surface tension of the jet, the bottom of the stable segment jet splits into multiple smaller whip-like jets. The diameter of these jets directly determines the fiber diameter deposited on the receiving platform.

[0038] Under high concentration, high injection rate, and low voltage process conditions, the high viscosity of the solution leads to a coarser diameter in the stable jet formed by the Taylor cone. At this point, the solute ratio in the solution is high, while the relative content of the conductive solvent is low. This results in the jet requiring a longer time to accumulate sufficient charge during flight to overcome surface tension and form filaments. The unstable whipping jets formed by these filaments eventually deposit on the receiving platform to form fibers. However, under these process conditions, as the charge accumulation time increases, the length of the stable jet also increases. Due to the relatively weak charge repulsion, the number of jets formed by filaments is relatively small, leading to a significant increase in the fiber diameter of the unstable whipping jet. This is one of the direct reasons for obtaining coarser fibers. However, with a fixed receiving distance, an increase in the stable jet length corresponds to a decrease in the unstable jet length. Simultaneously, the larger diameter of the formed jet results in lower solvent evaporation efficiency during the whipping process, preventing complete evaporation (after filamentation, the specific surface area increases, improving evaporation efficiency; if the fibers are coarse and there are few filaments, the specific surface area is small, resulting in lower evaporation efficiency). When fibers are deposited on the receiving platform, they are still in a high solvent content or even close to a solution state, which makes them prone to adhesion, collapse and morphological distortion, resulting in poor fiber forming effect and difficulty in obtaining large-diameter micron fibers with complete structure and clear outline.

[0039] To solve the above problems, the present invention mainly addresses the following aspects:

[0040] To increase fiber diameter, it is necessary to suppress charge-induced stretching and filament splitting. However, reducing filament splitting will significantly reduce the specific surface area of ​​the jet and weaken solvent evaporation, leading to adhesion, collapse and contour distortion caused by wet deposition. This invention proposes a synergistic mechanism that is different from conventional nanofiber preparation ideas: simultaneously controlling the charge-driven filament splitting and stretching intensity and the jet solidification speed under special temperature requirements in the same process, so that the coarse jet can obtain sufficient solidification support before reaching the collection end, thereby achieving both large diameter and molding integrity.

[0041] (1) Spinning solution viscosity: Under the premise of meeting the requirements for use in tissue engineering scaffolds, a low crystallinity polymer is used, and the viscosity of the spinning solution is controlled in a high range (3~6 Pa·s) so that the jet can still maintain continuous fiber formation under weak charge stretching conditions.

[0042] (2) Spinning solvent: In the selection of spinning solvent, existing technologies mainly focus on the influence of solvent conductivity and solubility on jet formation and stability during spinning, while neglecting the key role of solvent volatility (such as evaporation rate, boiling point, and mixed solvent ratio) on fiber drying and final forming quality under large-diameter micron fiber forming conditions. This invention takes solvent volatility and dielectric properties as the dominant variables for coarse-diameter forming: solvents with lower boiling points, higher vapor pressures, and lower dielectric constants are preferred to weaken the strong coulombic draw tendency brought about by high dielectric constant solvents, accelerate the solvent evaporation rate during jet whipping, and thus further suppress excessive fiber splitting and excessive thinning. It avoids the additional addition of solvents with high conductivity and high boiling points, such as N,N-dimethylformamide, to improve solution conductivity. In addition, the choice of solvent should also take into full consideration the dielectric constant of the solvent. Solvent systems with high dielectric constants are more likely to carry free charges and enhance repulsion, thereby promoting jet stretching and tending to finer fibers. Conversely, lower dielectric constants and lower conductivity will weaken this charge-driven overstretching, making it more physically sustainable to maintain a coarser jet.

[0043] (3) Existing processes typically use spinning temperatures that are only suitable for the forming requirements of nanoscale or smaller diameter fibers. When the fiber diameter increases to the micrometer level or even exceeds 10 μm, conventional spinning temperatures are insufficient to effectively promote the timely evaporation of residual solvents inside and between fibers, causing the fibers to easily stick together or deform due to solvent residue when they accumulate on the receiving platform. This invention uses forward solidification as the decisive factor in suppressing adhesion and collapse: since suppressing fiber splitting reduces the specific surface area and reduces evaporation efficiency, it is necessary to increase the in-transit evaporation flux to ensure that the jet reaches sufficient solidification before reaching the collector. Heating reduces surface tension on the one hand, and accelerates solvent evaporation on the other hand, and may terminate electric field stretching prematurely, resulting in an increase in fiber diameter and affecting process stability. Therefore, the following two points should be noted when setting the temperature: a) 2~8℃ below the solvent boiling point is optimal to achieve effective solvent evaporation; if the temperature is higher than the solvent boiling point, the solvent that has not yet formed a jet in the spinning injector will evaporate prematurely, affecting the spinning efficiency. b. The temperature should be at least 20°C below the melting point of the polymer solute to ensure stable fiber formation. If the spinning temperature is close to the polymer melting point, the fiber will melt, affecting the fiber formation effect. Maximize the in-transit evaporation driving force without triggering premature evaporation or blockage at the needle tip, moving the curing position forward to a section with sufficient flight path, thus allowing drying and curing to be completed even when the specific surface area is lowered due to inhibiting fiber splitting.

[0044] In summary, the key to the stable production of coarse-diameter microfibers (≥15 μm) under solution electrospinning conditions lies in the unconventional synergistic strategy of reducing fiber splitting and enhancing solvent evaporation. Firstly, a biodegradable polymer with low crystallinity and controlled molecular weight is selected, maintaining the spinning solution viscosity within a high viscosity window of 3–6 Pa·s. This ensures stable fiber formation and the creation of a coarser, stable jet even at high polymer concentrations. Secondly, a solvent combination with low boiling point / high vapor pressure and low dielectric constant (4–12) is preferentially selected to accelerate drying during the unstable jet whipping process and suppress excessive fiber splitting, thus balancing coarse diameter and forming integrity from the outset. Furthermore, the spinning temperature is set slightly below the solvent boiling point by 2–8 °C while maintaining a safety margin with the polymer melting point to further promote timely evaporation of residual solvent and reduce the risk of adhesion. By grounding the receiving roller at the receiving end to maintain a zero potential difference, premature attraction to the positively charged jet is weakened and the dwell time in the air is extended, thereby avoiding adhesion and morphological collapse of coarse fibers during deposition due to incomplete solvent removal, and finally achieving solution electrospinning to obtain fibers ≥15μm.

[0045] Beneficial effects:

[0046] (1) The present invention provides a method for preparing a micron-fiber biodegradable tissue engineering scaffold based on solution electrospinning. By increasing the solution concentration and injection speed, a low-boiling-point solvent is selected and a spinning temperature close to the boiling point is matched. By accelerating solvent evaporation and extending the whipping time of the jet in the air, the solvent is ensured to evaporate as soon as possible to achieve the molding of micron-fibers with a higher diameter (above 15 μm), while avoiding molding defects caused by fiber adhesion and solvent residue.

[0047] (2) The present invention provides a method for preparing a microfiber biodegradable tissue engineering scaffold based on solution electrospinning. The process is simple and improves the preparation efficiency of large-size microfiber scaffolds.

[0048] (3) The present invention has a wide range of applications for a solution electrospinning-based micron fiber biodegradable tissue engineering scaffold. Attached Figure Description

[0049] Figure 1 Here is a SEM image of the micron-sized fibers from Example 1;

[0050] Figure 2 Here is a SEM image of the micron-sized fibers from Example 2;

[0051] Figure 3 SEM image of the micron-sized fibers in Comparative Example 2;

[0052] Figure 4 SEM image of the micron-sized fiber in Comparative Example 3;

[0053] Figure 5 SEM image of the micron-sized fibers in Comparative Example 4;

[0054] Figure 6 SEM image of the micron-sized fiber in Comparative Example 6;

[0055] Figure 7 Here is a SEM image of the micron-sized fibers from Example 4;

[0056] Figure 8 This is a SEM image of the micron-sized fiber from Example 5. Detailed Implementation

[0057] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0058] The test methods involved in the performance indicators in the embodiments and comparative examples of this invention are as follows:

[0059] Viscosity: The spinning solutions prepared in each example were used as samples, and the viscosity of the prepared spinning solutions was measured according to the rotation method in the standard GB / T 10247-2008 viscosity measurement method.

[0060] Elongation at break: The prepared microfiber tissue engineering scaffold was used as a sample, and the elongation at break was tested according to the standard GB / T3923.1-2013 "Textiles - Tensile properties of fabrics - Part 1: Determination of breaking strength and elongation at break (strip method)".

[0061] Bursting strength: The prepared microfiber tissue engineering scaffold was used as a sample, and the bursting strength of the scaffold was measured according to GB / T 19976-2005 "Determination of bursting strength of textiles - steel ball method".

[0062] Tensile strength: Samples of the prepared microfiber tissue engineering scaffolds were taken separately, and the tensile strength of the scaffolds was measured in accordance with the standard GB / T1040.1-2018 "Determination of tensile properties of plastics - Part 1: General".

[0063] Elastic modulus: The prepared microfiber tissue engineering scaffold was used as a sample, and the elastic strength of the scaffold was measured in accordance with the standard GB / T1040.1-2018 "Determination of tensile properties of plastics - Part 1: General".

[0064] Degradation test: The prepared microfiber tissue engineering scaffold was used as a sample and then tested according to YY / T 1806.1-2021 "Evaluation method for in vitro degradation performance of biomedical materials - Part 1: Degradable polyesters". The degradation time was determined when the material mass loss reached 100%.

[0065] Example 1

[0066] The preparation method of biodegradable tissue engineering scaffolds based on solution electrospinning of micron fibers includes the following specific steps:

[0067] (1) Polycaprolactone with a number average molecular weight of 80,000 was dissolved in dichloromethane to prepare a spinning solution with a concentration of 50 wt%.

[0068] The dichloromethane has a boiling point of 40℃ and a vapor pressure of 429.53 mmHg; its dielectric constant is 8.9 F / m; and the viscosity of the spinning solution is 5.2 Pa·s.

[0069] (2) Load the spinning solution into the syringe and connect the positive high voltage electrostatic generator to the spinning nozzle with a specification of 21G. Keep the potential difference of the receiving roller ground wire at 0.

[0070] (3) Turn on the positive high voltage electrostatic generator to provide positive high voltage electrostatics to the spinning nozzle. After setting the spinning voltage, receiving distance, the angle between the radial direction of the spinning nozzle and the upper tangent of the receiving roller, and the speed of the spinning solution injection, perform electrostatic spinning and receive the formed micron fibers.

[0071] Electrospinning process parameters: spinning voltage is 12kV, receiving distance is 16cm, the angle between the radial direction of the spinning nozzle and the upper tangential plane of the receiving roller is 15°, the receiving roller speed is 250rpm, the spinning solution injection rate is 8mL / h, the spinning temperature is 38℃, and the spinning relative humidity is 18%.

[0072] (4) Based on the thickness requirement of 800 μm, a micron fiber biodegradable tissue engineering scaffold was obtained and dried in a vacuum oven at 37°C for 24 h.

[0073] like Figure 1 As shown, the final microfiber biodegradable tissue engineering scaffold has a fiber diameter of 23 μm; the elongation at break of the microfiber biodegradable tissue engineering scaffold is 700%, the tensile strength is 3.5 MPa, the bursting strength is 38 kPa, and the elastic modulus is 14 MPa; the degradation time of the microfiber biodegradable tissue engineering scaffold is 24 months, and after 3 months of degradation, the tensile strength, bursting strength, elongation at break, and elastic modulus of the microfiber tissue engineering scaffold are maintained at 80%, 80%, and 65% respectively; the obtained biodegradable tissue engineering scaffold can be used as wound dressing, tendon patch, pelvic floor patch, hernia patch, periodontal patch, or dura mater patch.

[0074] Comparative Example 1

[0075] A method for preparing a microfiber biodegradable tissue engineering scaffold based on solution electrospinning is basically the same as in Example 1, except that the viscosity of the spinning solution in step (1) is 2 Pa·s.

[0076] The final microfiber biodegradable tissue engineering scaffold has a fiber diameter of 6 μm, an elongation at break of 300%, a tensile strength of 1.5 MPa, and an elastic modulus of 10 MPa. After 3 months of degradation, the mechanical properties of the microfiber tissue engineering scaffold remain at 40%.

[0077] Comparing Comparative Example 1 and Example 1, it can be found that the fiber diameter of Comparative Example 1 is reduced and the mechanical strength is weakened. This is because after the viscosity of the spinning solution is reduced, the charge can more effectively overcome the surface tension of the jet in the stable section, and the number of splitting jets in the unstable section increases, resulting in a decrease in fiber diameter and a weakening of the mechanical properties it bears.

[0078] Comparative Example 2

[0079] A method for preparing a microfiber biodegradable tissue engineering scaffold based on solution electrospinning is basically the same as in Example 1, except that the viscosity of the spinning solution in step (1) is 7 Pa·s.

[0080] like Figure 3 As shown, the final microfiber biodegradable tissue engineering scaffold exhibits severe adhesion between fibers, making the fiber morphology almost invisible.

[0081] Comparing Comparative Example 2 and Example 1, it can be found that severe adhesion occurs between fibers, the fiber orientation is high, and the fibers are arranged in parallel, failing to present a random fiber distribution. This is because when the solution viscosity is too high, the positive voltage in the solution cannot overcome the surface tension of the solution, so there is no fiber splitting. Instead, the fibers are directly deposited on the receiving platform by a single stable jet. If the roller does not rotate, the fibers will accumulate at the same point. If the roller rotates, the fibers will be deposited in a completely oriented parallel arrangement, failing to form a random fiber structure. Furthermore, the fiber diameter of the stable jet reaches the scale of hundreds of meters, making it more difficult for the solvent to evaporate, often resulting in adhesion, and the fibers will be arranged in parallel.

[0082] Comparative Example 3

[0083] A method for preparing a microfiber biodegradable tissue engineering scaffold based on solution electrospinning is basically the same as in Example 1, except that: in step (1), the solvent is N,N-dimethylformamide and the boiling point of the solvent is 153°C.

[0084] like Figure 4 As shown, the final microfiber biodegradable tissue engineering scaffold does not have a clear fiber structure.

[0085] Comparing Comparative Example 3 and Example 1, it can be found that there is severe adhesion and fusion between the fibers. There are only a few circular holes, and there is no clear fiber overlap structure or through pore structure. This is because the fiber diameter is relatively large. During the jet whipping process, DMF cannot be effectively and timely volatilized, so the fibers deposited on the receiving platform are still not solidified, but in a liquid state. Therefore, after receiving, mutual fusion and adhesion between fibers will occur.

[0086] Comparative Example 4

[0087] A method for preparing a microfiber biodegradable tissue engineering scaffold based on solution electrospinning is basically the same as in Example 1, except that: in step (1), the solvent is dimethyl sulfoxide and the vapor pressure of the solvent is 0.42 mmHg.

[0088] like Figure 5 As shown, the final microfiber biodegradable tissue engineering scaffold does not have a clear fiber structure.

[0089] Comparing Comparative Example 4 and Example 1, it can be found that there is severe adhesion and fusion between the fibers. There are only a few circular holes, and there is no clear fiber overlap structure or through pore structure. This is because the fiber diameter is relatively large. During the jet whipping process, DMF cannot be effectively and timely volatilized, so the fibers deposited on the receiving platform are still not solidified, but in a liquid state. Therefore, after receiving, mutual fusion and adhesion between fibers will occur.

[0090] Comparative Example 5

[0091] A method for preparing a microfiber biodegradable tissue engineering scaffold based on solution electrospinning is basically the same as in Example 1, except that the spinning temperature and solvent boiling point are the same in step (3).

[0092] It is not possible to fabricate micron-fiber biodegradable tissue engineering scaffolds.

[0093] Comparing Comparative Example 5 and Example 1, it can be found that a large amount of blockage and uneven spinning occurred at the spinning needle, resulting in reduced fiber deposition efficiency. This is because the spinning temperature reaches the boiling point of the solvent, and the solvent evaporates rapidly at the spinning needle. The solvent evaporates at the needle before the Taylor cone is formed, causing the polymer to solidify and block the needle, resulting in low fiber formation efficiency.

[0094] Comparative Example 6

[0095] A method for preparing a microfiber biodegradable tissue engineering scaffold based on solution electrospinning is basically the same as in Example 1, except that the spinning temperature in step (3) is 10°C lower than the boiling point of the solvent.

[0096] The final microfiber biodegradable tissue engineering scaffold has a fiber diameter of 22 μm, an elongation at break of 400%, and a tensile strength of 4 MPa.

[0097] Comparison will be made between Example 6 and Example 1, such as... Figure 6 As shown, it can be seen that Comparative Example 6 can form a basic fiber structure, but adhesive chains will form between the fibers, and multiple fibers will fuse at the joint. This is because there is a large difference between the spinning temperature and the boiling point of the solvent. Although the temperature is high, it can only ensure that some solvent evaporates during the jet whipping process, and cannot effectively ensure that the fiber is fully formed. Therefore, a certain degree of fiber adhesive chains will be caused. After the fibers stick together, the fiber will not slip during the stretching process, but will break. Therefore, the breaking strength will increase.

[0098] Example 2

[0099] The preparation method of biodegradable tissue engineering scaffolds based on solution electrospinning of micron fibers includes the following specific steps:

[0100] (1) A spinning solution with a concentration of 55 wt% was prepared by dissolving polylactic acid with a number average molecular weight of 60,000 in tetrahydrofuran;

[0101] Among them, tetrahydrofuran has a boiling point of 66℃ and a vapor pressure of 162.18 mmHg; the dielectric constant of tetrahydrofuran is 7.6 F / m; and the viscosity of the spinning solution is 4.4 Pa·s.

[0102] (2) Load the spinning solution into the syringe and connect the positive high voltage electrostatic generator to the spinning nozzle with a specification of 21G. Keep the potential difference of the receiving roller ground wire at 0.

[0103] (3) Turn on the positive high voltage electrostatic generator to provide positive high voltage electrostatics to the spinning nozzle. After setting the spinning voltage, receiving distance, the angle between the radial direction of the spinning nozzle and the upper tangent of the receiving roller, and the speed of the spinning solution injection, perform electrostatic spinning and receive the formed micron fibers.

[0104] Electrospinning process parameters: spinning voltage is 8kV, receiving distance is 17cm, the angle between the radial direction of the spinning nozzle and the upper tangential plane of the receiving roller is 5°, the receiving roller speed is 200rpm, the spinning solution injection rate is 7mL / h, the spinning temperature is 60℃, and the spinning relative humidity is 20%.

[0105] (4) Based on the thickness requirement of 1000 μm, a micron fiber biodegradable tissue engineering scaffold was obtained and dried in a vacuum oven at 37°C for 24 h.

[0106] like Figure 2 As shown, the final microfiber biodegradable tissue engineering scaffold has a fiber diameter of 25 μm; the elongation at break of the microfiber biodegradable tissue engineering scaffold is 50%, the tensile strength is 6.5 MPa, the bursting strength is 50 kPa, and the elastic modulus is 21 MPa; the degradation time of the microfiber biodegradable tissue engineering scaffold is 18 months, and after 3 months of degradation, the tensile strength retention rate, bursting strength retention rate, elongation at break retention rate are 76%, and elastic modulus retention rate are 70%; the obtained biodegradable tissue engineering scaffold can be used as wound dressing, tendon patch, pelvic floor patch, hernia patch, periodontal patch, or dura mater patch.

[0107] Example 3

[0108] The preparation method of biodegradable tissue engineering scaffolds based on solution electrospinning of micron fibers includes the following specific steps:

[0109] (1) A spinning solution with a concentration of 45 wt% was prepared by dissolving poly(p-dioxanone) with a number average molecular weight of 50,000 in chloroform.

[0110] The boiling point of chloroform is 61℃, the vapor pressure is 194.23 mmHg, the dielectric constant of chloroform is 4.8 F / m, and the viscosity of the spinning solution is 3 Pa·s.

[0111] (2) Load the spinning solution into the syringe and connect the positive high voltage electrostatic generator to the spinning nozzle with a specification of 22G. Keep the potential difference of the receiving roller ground wire at 0.

[0112] (3) Turn on the positive high voltage electrostatic generator to provide positive high voltage electrostatics to the spinning nozzle. After setting the spinning voltage, receiving distance, the angle between the radial direction of the spinning nozzle and the upper tangent of the receiving roller, and the speed of the spinning solution injection, perform electrostatic spinning and receive the formed micron fibers.

[0113] Electrospinning process parameters: spinning voltage is 12kV, receiving distance is 18cm, the angle between the radial direction of the spinning nozzle and the upper tangential plane of the receiving roller is 10°, the receiving roller speed is 500rpm, the spinning solution injection rate is 8mL / h, the spinning temperature is 54℃, and the spinning relative humidity is 24%.

[0114] (4) Based on the thickness requirement of 600 μm, a micron fiber biodegradable tissue engineering scaffold was obtained and dried in a vacuum oven at 37°C for 24 h.

[0115] The final microfiber biodegradable tissue engineering scaffold has a fiber diameter of 20 μm; the elongation at break of the microfiber biodegradable tissue engineering scaffold is 500%, the tensile strength is 4 MPa, the bursting strength is 35 kPa, and the elastic modulus is 17 MPa; the degradation time of the microfiber biodegradable tissue engineering scaffold is 8 months, and after 3 months of degradation, the tensile strength retention rate, bursting strength retention rate, elongation at break retention rate are 60%, and elastic modulus retention rate is 68%; the obtained biodegradable tissue engineering scaffold can be used as wound dressing, tendon patch, pelvic floor patch, hernia patch, periodontal patch, or dura mater patch.

[0116] Example 4

[0117] The preparation method of biodegradable tissue engineering scaffolds based on solution electrospinning of micron fibers includes the following specific steps:

[0118] (1) A spinning solution with a concentration of 38wt% was prepared by dissolving polyglycolic acid with a number average molecular weight of 100,000 in hexafluoroisopropanol.

[0119] Among them, the boiling point of hexafluoroisopropanol is 58℃, the vapor pressure is 155.26 mmHg, the dielectric constant of hexafluoroisopropanol is 12 F / m, and the viscosity of the spinning solution is 6 Pa·s.

[0120] (2) Load the spinning solution into the syringe and connect the positive high voltage electrostatic generator to the spinning nozzle with a specification of 23G. Keep the potential difference of the receiving roller ground wire at 0.

[0121] (3) Turn on the positive high voltage electrostatic generator to provide positive high voltage electrostatics to the spinning nozzle. After setting the spinning voltage, receiving distance, the angle between the radial direction of the spinning nozzle and the upper tangent of the receiving roller, and the speed of the spinning solution injection, perform electrostatic spinning and receive the formed micron fibers.

[0122] Electrospinning process parameters: spinning voltage is 14kV, receiving distance is 19cm, the angle between the radial direction of the spinning nozzle and the upper tangential plane of the receiving roller is 15°, the receiving roller speed is 350rpm, the spinning solution injection rate is 9mL / h, the spinning temperature is 52℃, and the spinning relative humidity is 28%.

[0123] (4) Based on the thickness requirement of 400 μm, a micron fiber biodegradable tissue engineering scaffold was obtained and dried in a vacuum oven at 37°C for 24 h.

[0124] like Figure 7 As shown, the final microfiber biodegradable tissue engineering scaffold has a fiber diameter of 18 μm; the elongation at break of the microfiber biodegradable tissue engineering scaffold is 60%, the tensile strength is 8.8 MPa, the bursting strength is 44 kPa, and the elastic modulus is 25 MPa; the degradation time of the microfiber biodegradable tissue engineering scaffold is 6 months, and after 3 months of degradation, the tensile strength, bursting strength, elongation at break, and elastic modulus of the microfiber tissue engineering scaffold are maintained at 50%, 50%, and 80%, respectively; the obtained biodegradable tissue engineering scaffold can be used as wound dressing, tendon patch, pelvic floor patch, hernia patch, periodontal patch, or dura mater patch.

[0125] Example 5

[0126] The preparation method of biodegradable tissue engineering scaffolds based on solution electrospinning of micron fibers includes the following specific steps:

[0127] (1) Polycaprolactone with a number average molecular weight of 80,000 was dissolved in acetone to prepare a spinning solution with a concentration of 30 wt%.

[0128] The boiling point of acetone is 56℃, the vapor pressure is 229.52 mmHg, the dielectric constant of acetone is 12 F / m, and the viscosity of the spinning solution is 5 Pa·s.

[0129] (2) Load the spinning solution into the syringe and connect the positive high voltage electrostatic generator to the spinning nozzle with a specification of 24G. Keep the potential difference of the receiving roller ground wire at 0.

[0130] (3) Turn on the positive high voltage electrostatic generator to provide positive high voltage electrostatics to the spinning nozzle. After setting the spinning voltage, receiving distance, the angle between the radial direction of the spinning nozzle and the upper tangent of the receiving roller, and the speed of the spinning solution injection, perform electrostatic spinning and receive the formed micron fibers.

[0131] Electrospinning process parameters: spinning voltage is 16kV, receiving distance is 20cm, the angle between the radial direction of the spinning nozzle and the upper tangential plane of the receiving roller is 20°, the receiving roller speed is 400rpm, the spinning solution injection rate is 10mL / h, the spinning temperature is 48℃, and the spinning relative humidity is 30%.

[0132] (4) Based on the thickness requirement of 200 μm, micron fiber biodegradable tissue engineering scaffolds were obtained and dried in a vacuum oven at 37°C for 24 h.

[0133] like Figure 8 As shown, the final microfiber biodegradable tissue engineering scaffold has a fiber diameter of 15 μm; the elongation at break of the microfiber biodegradable tissue engineering scaffold is 300%, the tensile strength is 2.5 MPa, the bursting strength is 30 kPa, and the elastic modulus is 12 MPa; the degradation time of the microfiber biodegradable tissue engineering scaffold is 22 months, and after 3 months of degradation, the tensile strength retention rate, bursting strength retention rate, elongation at break retention rate is 68%, and elastic modulus retention rate is 50%; the obtained biodegradable tissue engineering scaffold can be used as wound dressing, tendon patch, pelvic floor patch, hernia patch, periodontal patch, or dura mater patch.

Claims

1. A method for preparing microfiber biodegradable tissue engineering scaffolds based on solution electrospinning, characterized in that: A spinning solution was prepared by dissolving the biodegradable polymer in a solvent, and a micron-fiber biodegradable tissue engineering scaffold was prepared by electrospinning. The viscosity of the spinning solution is 3~6 Pa·s; The solvent has a boiling point of 38~70℃ or a vapor pressure of 100~300mmHg; The dielectric constant of the solvent is 4~12 F / m; The spinning temperature is 2-8°C lower than the solvent boiling point and more than 20°C lower than the melting point of the biodegradable polymer; The microfiber biodegradable tissue engineering scaffold has a fiber diameter of more than 15 μm, and the fibers are continuous and uniformly distributed.

2. The method for preparing a microfiber biodegradable tissue engineering scaffold based on solution electrospinning according to claim 1, characterized in that, The fiber diameter in the microfiber biodegradable tissue engineering scaffold is 15~25μm.

3. The method for preparing a microfiber biodegradable tissue engineering scaffold based on solution electrospinning according to claim 2, characterized in that, The thickness of the microfiber biodegradable tissue engineering scaffold is 200~1000μm, the elongation at break is ≥50%, the tensile strength is 2.5~8.8MPa, and the elastic modulus is 12~25MPa; The degradation time of microfiber biodegradable tissue engineering scaffolds is 6 to 24 months, and the mechanical properties of microfiber tissue engineering scaffolds are maintained at 50 to 80% after 3 months of degradation.

4. The method for preparing a microfiber biodegradable tissue engineering scaffold based on solution electrospinning according to claim 3, characterized in that, The biodegradable polymers are polycaprolactone, polylactic acid, polydioxanone, or polyglycolic acid; the number average molecular weight of the biodegradable polymers is not higher than 100,000.

5. The method for preparing a microfiber biodegradable tissue engineering scaffold based on solution electrospinning according to claim 4, characterized in that, The solvent is dichloromethane, trichloromethane, hexafluoroisopropanol, tetrahydrofuran, or acetone.

6. The method for preparing a microfiber biodegradable tissue engineering scaffold based on solution electrospinning according to claim 5, characterized in that, The specific steps are as follows: (1) Prepare a spinning solution by dissolving the biodegradable polymer in a solvent; (2) Load the spinning solution into the syringe and connect the positive high voltage electrostatic generator to the spinning nozzle, and keep the potential difference of the receiving roller ground wire at 0; (3) Turn on the positive high voltage electrostatic generator to provide positive high voltage electrostatics to the spinning nozzle. After setting the spinning voltage, receiving distance, the angle between the radial direction of the spinning nozzle and the upper tangent of the receiving roller, and the speed of the spinning solution injection, perform electrostatic spinning and receive the formed micron fibers. (4) According to the thickness requirements, obtain a micron fiber biodegradable tissue engineering scaffold and dry it in a vacuum oven at 37°C for 24 hours.

7. The method for preparing a microfiber biodegradable tissue engineering scaffold based on solution electrospinning according to claim 6, characterized in that, The concentration of the spinning solution in step (1) is 30~55wt%.

8. The method for preparing a microfiber biodegradable tissue engineering scaffold based on solution electrospinning according to claim 6, characterized in that, In step (2), the spinning nozzle specification is 20G~24G.

9. The method for preparing a microfiber biodegradable tissue engineering scaffold based on solution electrospinning according to claim 6, characterized in that, In step (3), the spinning voltage is 8~16kV, the receiving distance is 16~20cm, the angle between the radial direction of the spinning nozzle and the upper tangent of the receiving roller is 0°~20°, the spinning solution injection speed is 6~10mL / h, the spinning temperature is 35~60℃, and the spinning relative humidity is 18~30%.

10. The application of the biodegradable tissue engineering scaffold prepared by the method according to any one of claims 1 to 9, characterized in that: Used as wound dressings, tendon patches, pelvic floor patches, hernia patches, periodontal patches, or dura mater patches.

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