DEVICE AND METHOD FOR PRODUCING AN ANISOTROPIC FIBER SCROLL BY ELECTROSPINNING

Description

[0001] The invention relates to a device and a method for producing a tubular fiber scaffold by electrospinning.

[0002] Electrospinning is a technology for producing fibers from natural and synthetic polymers with diameters ranging from approximately 30 nm to 3 µm. Fiber formation occurs by accelerating the charge carriers induced in the polymer in a strong electric field, which ultimately leads to the stretching of the viscoelastic material. In the simplest case, the electric field is generated by applying a high voltage between a reservoir containing the polymer solution and a deposition spindle onto which the fibers are deposited.

[0003] The reservoir is connected to a spinneret through which the polymer solution jet emerges. The properties of the resulting fibers (diameter, fiber spacing, homogeneity, etc.) can be influenced by the choice of spinning parameters (e.g., distance between the reservoir and the deposition spindle, viscosity, surface tension and conductivity of the polymer solution, selected high voltage, etc.).

[0004] The production of medical vascular prostheses, in particular, requires the creation of anisotropic, usually tubular fiber scaffolds (so-called grafts or stent grafts). To produce tubular fiber scaffolds by electrospinning, the use of a rotatable deposition spindle onto which the material beam is deposited is known. The deposition spindle is elongated and rod-shaped and is also called a mandrel.

[0005] To create an electrical potential difference between the spinneret and the deposition spindle, the spinneret is connected to the first electrical pole of a two-pole DC voltage source. This can, in particular, be a variably adjustable high-voltage generator. The polymer solution can be subjected to a positive or negative high voltage, creating a potential difference between the reservoir or spinneret and the deposition spindle.

[0006] US 2010 / 222771 A1 describes a method for controlled electrospinning. WO 2009 / 102365 A2 describes a method and devices for the controlled production of fibers. WO 2018 / 185223 A1 describes an electrospinning printing device. Tubular structures produced by electrospinning are described in TEO WE et al., "Porous tubular structures with controlled fiber orientation using a modified electrospinning method, Tubular structures with controlled orientation through electrospinning," Nanotechnology, Institute of Physics Publishing, 16, 2005, pp. 918-924. WO 2019 / 014686 A1 also describes an electrospinning process.

[0007] It has been shown that the biocompatibility of the produced grafts, and in particular the ingrowth of autologous cells into the grafts, depends on the local structuring of the produced fiber scaffold. Consequently, one of the objects of the invention is to create a method and a corresponding device that are as simple and robust as possible and enable local structuring of the produced fiber scaffold.

[0008] According to the invention, this object is achieved by a device according to claim 1 and a method according to claim 8.

[0009] A device according to the invention is designed for producing an anisotropic fiber scaffold, in particular a vascular prosthesis, by electrospinning. It comprises a reservoir, a spinneret for delivering a material jet, and an electrically conductive deposition spindle rotatable relative to the spinneret. At least one electrical DC voltage source is provided for providing an electrical potential difference between the spinneret and the deposition spindle. This can, in particular, be a variable bipolar high-voltage source.

[0010] Furthermore, a housing is provided that at least partially encloses the deposition spindle and the spinneret, wherein the housing is preferably grounded. A controlled switching unit is provided, which is designed to alternately connect the deposition spindle to the DC voltage source during electrospinning, i.e., to set it to a defined potential, and to disconnect it from it again, i.e., to leave the deposition spindle floating. The deposition spindle can consist of or comprise an electrically conductive material, for example, steel, aluminum, or copper. The deposition spindle can also be referred to as a deposition electrode.

[0011] In particular, two embodiments can be provided according to the invention: In a ersten Ausführungsform the spinneret is connected to a first electrical pole (e.g. the positive pole) of the DC voltage source and the deposition spindle is connected to a second electrical pole (e.g. the negative pole) of the DC voltage source. The switching unit is designed to connect the second electrical pole of the DC voltage source to the deposition spindle at least once, preferably several times, during electrospinning and to disconnect it from the deposition spindle again after a certain period of time. In particular, the deposition spindle is thereby switched between the ground potential (0 V) and an undefined potential (floating). This embodiment can be provided when the potential difference that can be generated by the DC voltage source (e.g. 15 kV) is sufficient for the spinning process; during the spinning process, the spinneret is at +15 kV and the deposition spindle is at 0 V or floating.

[0012] In one zweiten Ausführungsform Two DC voltage sources are provided, wherein the spinneret is connected to a first electrical pole (e.g., the positive pole) of the first DC voltage source, and the deposition spindle is connected to a first electrical pole (e.g., the positive pole) of the second DC voltage source. The switching unit is designed to connect the first electrical pole of the second DC voltage source to the deposition spindle at least once, preferably several times, during electrospinning and to disconnect it from the deposition spindle again after a certain period of time.

[0013] This second embodiment can be used particularly when the potential difference generated by the DC voltage source (e.g., 15 kV) is insufficient for the spinning process; in this case, two DC voltage sources are used. During the spinning process, the spinneret is at +15 kV, and the deposition spindle is at a potential value below 0 V, for example, -2 kV, or floating, so that a potential difference of 17 kV is generated. The second electrical poles of the DC voltage sources (the negative poles) are electrically connected.

[0014] By switching between 0 V (or a negative potential) and an undefined (floating) potential during electrospinning, the structural properties of the resulting fiber framework change during the spinning process. This allows the thickness, texture, and mechanical properties of the resulting fiber framework to be easily modified, purely electrically and without mechanical intervention.

[0015] For example, it has been shown that some materials tend to form waves or lobes during electrospinning when the deposition spindle is at GND potential. This means that the outer circumference of the fiber structure becomes irregular, and the fiber structure extends inhomogeneously outwards in the radial direction. Surprisingly, the inventive switching of the second electrical pole of the DC voltage source after a certain spinning time has been shown to suppress the formation of waves or lobes on the outer circumference, as they adhere to the original cylindrical fiber structure, forming cavities in the fiber structure. With appropriately selected time periods, cavities with a typical diameter of over 5 µm are formed.

[0016] By selecting the time between switching, the size of the cavities formed by the lobes in the fiber framework can be varied. In particular, it has been shown that the longer the second pole is connected to the deposition spindle, the larger the lobes and thus the cavities.

[0017] In other words, when the deposition spindle is at a defined potential (especially GND or a potential below 0 V), irregularities form in the fiber framework, which are closed when the deposition spindle is separated from the defined potential and floats. This closure of the irregularities creates cavities whose expansion can be influenced by switching the voltage ratios.

[0018] Since the resulting waves or flaps exhibit different macroscopic properties than the basic scaffold, such as varying strength and elasticity, intermediate layers with the desired properties can be specifically created within the fiber scaffold. Both the resulting cavities and the intermediate layers in the fiber scaffold offer advantages when using the resulting fiber scaffolds as vascular prostheses, for example, with regard to their biocompatibility or adaptation to the flexibility of the treated vessels.

[0019] According to the invention, a return electrode can be provided, arranged behind the deposition spindle with respect to the ejected material jet. Such a return electrode can serve to stabilize the material jet when the deposition spindle is at an undefined potential, i.e., floating. For this purpose, the switching unit is designed to connect the second electrical pole of the DC voltage source, or the first electrical pole of the second DC voltage source, to the return electrode during electrospinning, or when the deposition spindle is floating.

[0020] According to the invention, a housing is provided that at least partially encloses the deposition spindle and the spinneret. The housing can be connected to the second electrical pole (negative pole or GND) of the DC voltage source or to the second electrical poles (negative pole or GND) of the DC voltage sources. In particular, the housing can be grounded. This ensures that the housing of the device is grounded, i.e., at a potential of 0 V, thus forming a "Faraday cage."

[0021] The potential difference thus generated can be approximately 5 kV to 20 kV, preferably 8 kV to 17 kV, particularly preferably 10 kV to 15 kV, wherein the potential at the deposition spindle is preferably smaller than the potential at the spinneret, in particular smaller than or equal to 0 V, for example -2 kV.

[0022] The switching of the DC voltage source(s) can be done manually or by an electronic control unit. Such an electronic control unit can be provided, in particular, to control at least the DC voltage source(s) and the switching unit. However, the control unit can also control other elements of the device according to the invention, for example, a valve of the reservoir for controlling the discharge of the material, or motors for rotating and / or displacing the separation spindle.

[0023] The separation spindle can be designed as a spindle that is rotatable relative to the spinneret and that is rotatable along an axis extending substantially orthogonally to the ejected material jet and / or displaceable along this axis. In particular, the separation spindle can be moved back and forth along this axis in a sinusoidal or triangular oscillation pattern to produce an elongated fiber framework.

[0024] A sinusoidal oscillation pattern of the displacement results in expanded end regions of the fiber scaffold, which can subsequently serve as support rings for the vascular prosthesis. Alternatively or additionally, the return electrode can be moved back and forth along this axis in a sinusoidal or triangular oscillation pattern to create the elongated extension of the fiber scaffold. Furthermore, by slowing or reducing the oscillation of the displacement at predetermined locations, a local thickening of the vessel wall thickness can be achieved. The resulting support rings prevent collapse or external compression of the vessel in the patient. The deposition spindle can also be displaceable in the direction of the material jet to adjust the distance between the spinneret and the deposition spindle.

[0025] The deposition spindle can have a diameter of approximately 2 mm and a rotational speed of approximately 250 revolutions per minute during electrospinning. The distance between the spinneret and the deposition spindle can be approximately 5 cm to 12 cm, for example, approximately 8 cm. The diameter of the deposition spindle can also be significantly larger, for example, 5 mm, 10 mm, 20 mm, 30 mm, or 36 mm, for example, if the vascular prosthesis is to be inserted into the aorta of an adult. In particular, a deposition spindle diameter of approximately 2 mm can be intended for the creation of vascular prostheses to replace smaller vessels (arteries, but also veins, lymphatic vessels, or cerebrospinal fluid drainage systems). Alternatively, a diameter of approximately 4 mm to approximately 8 mm can be intended for medium-sized vessels and dialysis shunts, but larger diameters can be used for replacing sections of the aorta, the pulmonary artery, or the large veins.

[0026] If a larger separation spindle diameter is selected, the rotational speed is preferably also reduced accordingly to achieve a substantially constant peripheral speed. For example, with a separation spindle diameter of approximately 5 mm, a rotational speed of approximately 80–120 revolutions per minute can be provided. For larger diameters, multiple spinnerets can also be provided.

[0027] In the area between the spinneret and the deposition spindle, stabilizing electrodes can also be provided, which are preferably plate-shaped and are preferably connected to the first electrical pole or the second electrical pole of the DC voltage source(s). Such stabilizing electrodes can serve to stabilize and, if necessary, focus the ejected material jet.

[0028] The ejected material can be a mixture of a polymer and a solvent. For example, the material jet can comprise a solution of 5 wt.% polydioxanone (PDS) in hexafluoropropanol, or a solution of 5 wt.% thermoplastic polyurethane (TPU) in hexafluoropropanol.

[0029] The invention further relates to a method for producing an anisotropic fiber scaffold, in particular a vascular prosthesis by electrospinning, wherein a material jet is guided from a reservoir via a spinneret onto a rotating, electrically conductive deposition spindle, and wherein an electrical potential difference is formed between the spinneret and the deposition spindle by connecting the spinneret and the deposition spindle to a preferably variable, two-pole electrical direct voltage source.

[0030] According to the invention, a controlled switching unit is provided which connects the deposition spindle to the direct voltage source at least once, preferably several times, during the spinning process and disconnects it again after a predetermined period of time. This change in the electrical potential difference between the deposition spindle and the spinneret during electrospinning achieves local structuring of the deposited fiber structure.

[0031] In a first embodiment, the potential difference is created by connecting the spinneret to a first electrical pole of the DC voltage source and the deposition spindle to a second electrical pole of the DC voltage source. The switching unit connects the second electrical pole (negative pole, GND) of the DC voltage source to the deposition spindle and disconnects it again after a certain period of time. By changing the electrical potential difference between the deposition spindle and the spinneret once or repeatedly during electrospinning, local structuring of the deposited fiber structure can be achieved.

[0032] In an alternative embodiment of the method according to the invention, the potential difference is formed by connecting the spinneret to a first electrical pole of a first DC voltage source and connecting the deposition spindle to a first electrical pole of a second DC voltage source.

[0033] During electrospinning, the switching unit connects the first electrical pole of the second DC voltage source to the deposition spindle at least once, preferably several times, and disconnects it from the latter again after a certain period of time.

[0034] In both embodiments, it can be provided that the switching unit separates the second electrical pole of the DC voltage source, or the first electrical pole of the second DC voltage source, from the deposition spindle at least once, preferably several times, and connects it to a return electrode arranged behind the deposition spindle with respect to the material jet.

[0035] During electrospinning, the deposition spindle can rotate relative to the spinneret along an axis substantially orthogonal to the ejected material jet and / or be displaced along this axis. In particular, the deposition spindle can be moved back and forth along this axis in a sinusoidal or triangular oscillation pattern. Alternatively or additionally, the return electrode can also be moved back and forth along this axis in a sinusoidal or triangular oscillation pattern.

[0036] During electrospinning, the switching unit can connect the deposition spindle to the DC voltage source for a first time period t 1 and then disconnect the deposition spindle from the DC voltage source for a second time period t 2 . The time periods t 1 and t 2 can each be approximately 5 to 10 minutes. The process can be repeated approximately 5 to 10 times.

[0037] Of course, the process can also be carried out in reverse order, whereby the switching unit first disconnects the separation spindle from the DC voltage source for a time period t 2 and then connects the separation spindle to the DC voltage source for a time period t 1.

[0038] The time periods t 1 and t 2 can also be different. For example, the time period t 1 can be approximately 5 to 10 minutes, and the time period t 2 can be approximately 2 to 5 minutes.

[0039] However, the time duration t 2 is preferably shorter than the time duration t 1 . The total duration of the electrospinning process can be the sum of t 1 and t 2 . The switching unit can be configured to adjust these time durations and the switching time differently depending on the application and the spun material, whereby corresponding values ​​can be obtained, for example, from a database.

[0040] The rotational speed of the separation spindle can be approximately 250 revolutions per minute, and the diameter of the separation spindle can be approximately 2 mm, 5 mm, 10 mm, 20 mm, 30 mm, or 36 mm. The flow rate of the material jet from the reservoir can be approximately 0.5 - 2 ml / h, in particular approximately 0.7 ml / h.

[0041] Further features of the invention emerge from the claims, the following description of the embodiments, and the figures. They show: Fig. 1a a schematic representation of a first embodiment of a device according to the invention; Fig. 1b a schematic representation of a second embodiment of a device according to the invention; Fig. 1c a schematic representation of a third embodiment of a device according to the invention; Fig. 1d a schematic representation of a fourth embodiment of a device according to the invention; Figs. 2a - 3b Microscopic images of a cross-section of two fiber scaffolds produced using conventional methods; Figs. 4a - 4b microscopic images of a cross-section of a fiber scaffold produced using a method according to the invention.

[0042] Fig. 1a shows a schematic representation of a first embodiment of a device according to the invention. The device is designed for producing an anisotropic fiber scaffold 10 in the form of a vascular prosthesis by electrospinning and comprises a reservoir 1 in which a polymer solution is provided, and a spinneret 2 connected thereto for delivering a material jet. The spinneret 2 is connected to a first pole of an electrical DC voltage source 4, here the positive pole of this DC voltage source 4.

[0043] The negative pole of the DC voltage source 4 is grounded (GND) and connected to a housing 7. A rotatable separation spindle 3 is provided at a distance of approximately 8 cm from the spinneret 2. The DC voltage source 4 provides a high voltage of approximately 8 kV.

[0044] The separation spindle 3 is electrically conductive, for example made of steel, and is connected to the housing 7, i.e., the negative pole of the DC voltage source 4, via a switching unit 5. An electrical potential difference forms between the spinneret 2 and the separation spindle 3, which causes material emerging from the spinneret 2 to be discharged in the form of a material jet 8 onto the rotating separation spindle 3. As the separation spindle 3 rotates, the material jet 8 winds up and forms a schematically illustrated tubular fiber structure 10. The length of the produced fiber structure 10 can be adjusted by the periodic sinusoidal or triangular displacement of the separation spindle 3 along the axis 9, indicated by a double arrow.

[0045] A controlled electronic switching unit 5 is provided, which is designed to connect the second electrical pole of the DC voltage source 4 to the electrically conductive deposition spindle 3 and to disconnect it again during electrospinning. In other words, the deposition spindle alternates between a state (a) in which it is held at GND potential and a state (b) in which it floats freely.

[0046] In state (b), a material jet 8 is nevertheless formed, since in this case a potential difference occurs between the spinneret 2 and the housing 7, so that the material jet 8 is attracted by the housing 7 and strikes the separation spindle 3.

[0047] In state (a), a structure develops with surface faults, which were observed as waves or radially outward-directed, longitudinal lobes. In state (b), a largely uniform structure forms without major voids.

[0048] By switching at least once between state (a) and state (b), flap formation occurs only in state (a), while in state (b) the formed flaps fold homogeneously over the existing fiber framework. This leads to the formation of smaller or larger cavities in the peripheral wall of the fiber framework.

[0049] Fig. 1b shows a schematic representation of a second embodiment of a device according to the invention. This largely corresponds to the first embodiment with the difference that an electrically conductive back electrode 6 is provided, arranged behind the deposition spindle 3 with respect to the ejected material jet 8. The switching unit 5 switches the second electrical pole (the negative pole) of the DC voltage source 4 between the deposition spindle 3 and the back electrode 6. In state (b), i.e. when the deposition spindle 3 is floating, fibers also form between the back electrode 6 and the deposition spindle 3, which are wound up by the latter due to its rotation; however, no lobes are formed. The length of the produced fiber framework 10 can be adjusted by the periodic sinusoidal or triangular displacement of the back electrode 6 parallel to the axis 9, indicated by a double arrow.

[0050] Fig. 1c und Fig. 1d show schematic representations of a third and fourth embodiment of a device according to the invention. These embodiments correspond to those of Fig. 1a und Fig. 1b , but with two DC voltage sources 4a, 4b. This allows the generation of higher potential differences than with a single DC voltage source.

[0051] The spinneret 2 is connected to the first electrical pole of the first DC voltage source 4a, and the deposition spindle 3 is connected to a first electrical pole of the second DC voltage source 4b. The switching unit 5 is designed to alternately connect and disconnect the first electrical pole of the second DC voltage source 4b to the deposition spindle 3 during electrospinning.

[0052] In the embodiment according to Fig. 1d A return electrode 6 is provided, arranged behind the deposition spindle 3 with respect to the ejected material jet 8, wherein the switching unit 5 is designed to alternately connect the first electrical pole of the second DC voltage source 4b to the deposition spindle 3 during electrospinning, to disconnect it from the deposition spindle 3, and to connect it to the return electrode 6. In this exemplary embodiment, both the deposition spindle 3 and the return electrode 6 can be periodically displaced in a sinusoidal or triangular manner along the direction indicated by double arrows in order to adjust the length of the produced fiber framework 10.

[0053] In both embodiments according to Fig. 1c und Fig. 1d a housing 7 is provided which partially encloses the separation spindle 3 and the spinneret 2, wherein the housing is connected to the second electrical poles (the negative poles) of the DC voltage sources 4a, 4b and is grounded via a GND connection.

[0054] In an embodiment of the invention not shown, 5 wt. % thermoplastic polyurethane (TPU, described in S. Baudis et al., Hard-block degradable thermoplastic urethane-elastomers for electrospun vascular prostheses, J. Polym. Sci. Part A Polym. Chem. 50 (2012) 1272-1280) was dissolved in hexafluoroisopropanol and processed using an electrospinning device according to the invention into continuous nanofibers, which were wound into a tube on the rotating deposition spindle. The distance between the needle tip of the spinneret and the deposition spindle was approximately 8 cm. The electrospinning device was placed as a whole in a Faraday cage (housing) and operated in a class 1000 cleanroom at a temperature of 24 °C and 34% RH. The flow of polymer solution into the spinneret was set to approximately 0.7 ml / h and a voltage of approximately 12 kV was applied to the spinneret.The electrospun tube thus obtained on the deposition spindle had an inner diameter of 1.5 mm and a wall thickness of approximately 300 µm.

[0055] Figs. 2a - 3b show microscopic images of a cross-section in full view and in magnified view of various fiber scaffolds produced using conventional methods.

[0056] In the fiber framework according to Figs. 2a - 2b The deposition spindle 3 was kept at GND potential throughout the entire spinning process, corresponding to the above-defined condition (a). This results in a fiber structure with numerous radial waves or lobes running in the longitudinal direction of the formed tubular fiber structure. In the fiber structure according to Figs. 3a - 3b The deposition spindle 3 was kept floating, i.e., without a dedicated potential, throughout the entire spinning process, in accordance with the above-defined condition (b). A return electrode was provided that was kept constantly at GND potential during the spinning process. This resulted in a fiber framework without distortion.

[0057] Figs. 4a - 4b show microscopic images of a cross-section in full view and in an enlarged view of various fiber scaffolds produced by a method according to the invention. In the fiber scaffold according to Figs. 4a - 4bThe deposition spindle 3 was held at GND potential for a time t 1 during the spinning process and then kept floating for a time t 2 . The electrospinning process extended over the period t 1 + t 2 . The values ​​of t1 and t2 were approximately 5 minutes and 15 minutes, respectively; the entire spinning process approximately 20 minutes. The result is a fiber scaffold with numerous cavities in the outer wall, which run in the longitudinal direction of the formed tubular fiber scaffold, but without external distortions. Such a fiber scaffold can be used particularly advantageously in vascular surgery, since the cavities promote, among other things, the ingrowth of human tissue. However, the invention is not limited to the illustrated embodiments, but encompasses all devices and methods within the scope of the following patent claims. In particular, the invention is not limited to devices and methods for producing vascular prostheses. List of reference symbols

[0058] 1Reservoir 2Spinning nozzle 3Deposition spindle 4a, 4bDC voltage source 5Switching unit 6Return electrode 7Housing 8Material jet 9Axis 10Fiber framework 11Control unit

Claims

1. A device for producing an anisotropic fibre structure (10), in particular a vascular prosthesis, by electrospinning, comprising a reservoir (1), a spinneret (2) for ejecting a material jet (8) and an electrically conductive separating spindle (3) rotatable relative to the spinneret (2), wherein at least one preferably variable, two-pole electrical DC voltage source (4, 4a, 4b) for providing an electrical potential difference between the spinneret (2) and the separating spindle (3) is provided, and wherein a preferably grounded housing (7) at least partially enclosing the separating spindle (3) and the spinneret (2) is provided, characterised in that a controlled switching unit (5) is provided which is designed to disconnect the separating spindle (3) from the DC voltage source (4, 4a, 4b) at least once, preferably several times, during electrospinning.

2. The device according to claim 1, characterised in that the spinneret (2) is connected to a first electrical pole of the DC voltage source (4) and the separating spindle (3) is connected to a second electrical pole of the DC voltage source (4), wherein the switching unit (5) is designed to disconnect the second electrical pole of the DC voltage source (4) from the separating spindle (3) at least once, preferably several times, during electrospinning.

3. The device according to claim 1, characterised in that two DC voltage sources (4a, 4b) are provided, wherein the spinneret (2) is connected to a first electrical pole of the first DC voltage source (4a) and the separating spindle (3) is connected to a first electrical pole of the second DC voltage source (4b), and wherein the switching unit (5) is designed to disconnect the first electrical pole of the second DC voltage source (4b) from the separating spindle (3) at least once, preferably several times, during electrospinning.

4. The device according to claim 2 or 3, characterised in that a back electrode (6) is provided behind the separating spindle (3) with respect to the ejected material jet (8), the switching unit (5) being designed to disconnect a. the second electrical pole of the DC voltage source (4) or b. the first electrical pole of the second DC voltage source (4b) from the separating spindle (3) at least once, preferably several times, during electrospinning and to connect it to the back electrode (6).

5. The device according to one of claims 2 to 4, characterised in that the housing (7) is connected a. to the second electrical pole of the DC voltage source (4) or b. to the second electrical poles of the DC voltage sources (4a, 4b).

6. The device according to one of claims 1 to 5, characterised in that the potential difference is approximately 5 kV to 20 kV, preferably 8 kV to 17 kV, particularly preferably 10 kV to 15 kV, wherein the potential across the separating spindle (3) is preferably lower than the potential across the spinneret (2), in particular lower than or equal to 0 V, for example -2 kV.

7. The device according to one of claims 1 to 6, characterised in that the separating spindle (3) is rotatable in an axis (9) extending substantially orthogonally to the ejected material jet (8) and / or is displaceable along this axis (9), wherein the separating spindle (3) is reciprocally movable in particular along the axis (9) in a sinusoidal or triangular oscillation.

8. The device according to one of claims 1 to 7, characterised in that the controlled switching unit (5) is designed to alternately connect and disconnect the separating spindle (3) to / from the DC voltage source (4, 4a, 4b) during electrospinning, and / or in that an electronic control unit (11) is provided in particular for controlling at least the DC voltage source (4, 4a, 4b) and the switching unit (5).

9. A method of producing an anisotropic fibre structure (10), in particular a vascular prosthesis, by electrospinning, wherein a material jet (8) is guided from a reservoir (1) via a spinneret (2) onto a rotating, electrically conductive separating spindle (3), wherein an electrical potential difference is formed between the spinneret (2) and the separating spindle (3) by connecting the spinneret (2) and the separating spindle (3) to a preferably variable, two-pole electrical DC voltage source (4, 4a, 4b), characterised in that a controlled switching unit (5) disconnects the separating spindle (3) from the DC voltage source (4, 4a, 4b) at least once, preferably several times, during electrospinning, so that local structuring of the deposited fibre structure (10) is achieved by changing the electrical potential difference between the separating spindle (3) and the spinneret (2) during electrospinning.

10. The method according to claim 9, characterised in that the potential difference is formed by connecting the spinneret (2) to a first electrical pole of the DC voltage source (4) and by connecting the separating spindle (3) to a second electrical pole of the DC voltage source (4), wherein the switching unit (5) disconnects the second electrical pole of the DC voltage source (4) from the separating spindle (3) at least once, preferably several times, during electrospinning.

11. The method according to claim 10, characterised in that the potential difference is formed by connecting the spinneret (2) to a first electrical pole of a first DC voltage source (4a) and connecting the separating spindle (3) to a first electrical pole of a second DC voltage source (4b), wherein the switching unit (5) disconnects the first electrical pole of the second DC voltage source (4b) from the separating spindle (3) at least once, preferably several times, during electrospinning.

12. The method according to claim 10 or 11, characterised in that the switching unit (5) disconnects the second electrical pole of the DC voltage source (4) or the first electrical pole of the second DC voltage source (4b) from the separating spindle (3) at least once, preferably several times, during electrospinning and connects it to a back electrode (6) arranged behind the separating spindle (3) with respect to the material jet (8).

13. The method according to one of claims 9 to 12, characterised in that the separating spindle (3) rotates relative to the spinneret (2) along an axis (9) extending approximately orthogonally to the ejected material jet (8) and / or is displaced along this axis (9) during electrospinning, in particular in that the separating spindle (3) is reciprocated along the axis (9) in a sinusoidal or triangular oscillation.

14. The method according to one of claims 9 to 13, characterised in that the switching unit (5) connects the separating spindle (3) to the DC voltage source (4, 4a, 4b) for a first time period t1 during electrospinning, and then disconnects the separating spindle (3) from the DC voltage source (4, 4a, 4b) for a second time period t2, the time periods t1, t2 each being approximately 5 to 10 minutes and this process being repeated 5 to 10 times to produce the fibre structure (10), and / or in that the delivery rate of the material jet (8) from the reservoir (1), is preferably approximately 0.5- 2 ml / h, in particular approximately 0.7 ml / h.

15. The method according to one of claims 9 to 14, characterised in that the material jet (8) comprises a polymer-solvent mixture, in particular - a solution of 5% by weight of polydioxanone (PDS) in hexafluoro2propanol, or - a solution of 5% by weight of thermoplastic polyurethane (TPU) in hexafluoro2propanol.