NL2010830C2

NL2010830C2 - Method and device for depositing a material on a target and medical device obstainable therewith.

Info

Publication number: NL2010830C2
Application number: NL2010830A
Authority: NL
Inventors: Johannes Cornelis Maria Marijnissen; Wilfred Peter Heiner
Original assignee: Alvimedica Vascular Res B V
Priority date: 2013-05-21
Filing date: 2013-05-21
Publication date: 2014-11-26
Also published as: WO2014189375A1

Abstract

The invention relates to a method for depositing a coating material on a medical device, a depositing system for depositing a coating on a medical device and a coated medical device. The method comprises the steps of: - providing the medical device in a spray chamber; - providing the coating material to an electrospray nozzle; - applying an electric potential to the nozzle; and - ejecting the coating material from the electrospray nozzle towards the medical device for coating a surface of the medical device; characterized in that the method further comprises - providing ions in the spray chamber to subject said surface to be coated to ions to prevent the formation of holes or cracks in the deposited coating material.

Description

METHOD AND DEVICE FOR DEPOSITING A MATERIAL ON A TARGET AND MEDICAL DEVICE OBTAINABLE THEREWITH

The invention relates to a method for depositing material on a target.

A known method for depositing a material on a target, e.g. a substrate, is electrospraying. In electrospraying, the material to be deposited is provided in a nozzle. A high voltage electric potential is applied to the nozzle, usually in the order of 1-30 kV. Due to this electric potential, the material in the nozzle obtains an electrical charge. In some cases, the electrical forces force the material out of the nozzle. Additionally or alternatively, the material is forced out mechanically, e.g. by using a syringe. The material then forms small droplets which repel each other due to their like charges. The result is a very fine spray. The target is electrically conducting and connected to ground. Therefore, the charged particles of the coating material are drawn towards the target, where they are deposited.

A related method known in the art is electrospinning. The basic principle of electrospinning is the same as for electrospraying. However, whereas in electrospraying the material is formed as spray of fine particles, in electrospinning a polymer material is used which forms very fine fibers, e.g. nanofibers, when ejected from the nozzle. The target is again electrically conducting and connected to ground to draw the fibers to the target.

A drawback of these known methods is that they cannot be applied to non-conductive, i.e. electrically insulating targets .

Moreover, coating an electrically conducting target with an insulating coating material using conventional methods results in a coating with cracks or openings.

For example, the coating applied to a medical device, i.e. a stent or other implantable device or a catheter, needs to be free of cracks. Moreover, these devices often comprise insulating parts, which cannot be coated using the above conventional methods.

A goal of the invention is to overcome these drawbacks and provide a method for depositing material on a target, which also gives satisfactory results for insulating coating materials and/or insulating targets.

This goal is achieved with the method according to the invention for depositing material on a target, comprising the steps of: - providing the target in a spray chamber; - providing the material to an electrospray nozzle; - applying an electric potential to the nozzle; and - ejecting the material from the electrospray nozzle towards the target; characterized in that the method further comprises - providing ions in the spray chamber.

The formation of holes or cracks occurring in conventional methods when applying an insulating coating to a conducting target is believed to be caused by a phenomenon called back ionization (sometimes called back sparking).

Back ionization occurs because the layers of coating material isolate the conducting target as they are build up on the target. The layers on the target therefore obtain a high charge, which can result in an electrical discharge through the deposited layers. This leads to a coating with cracks or openings .

According to the inventors, subjecting the target to ions neutralizes the charge build up in the layers of coating material. Thereby, back ionization is prevented.

On the other hand, in case of an insulating target, the ions will charge the surface of the target such that the coating material is attracted by the target's surface. When a layer of coating material is deposited, this initial charge will be at least partially neutralized. A new load of ions will attach to this first layer to again establish a net charge, on which a second layer will be deposited, and the process repeats itself.

Moreover, some of the charged particles ejected from the nozzle may be (partially) neutralized in flight by the ions in the spray chamber. Also, the charge at the surface of the target may be (partially) released through the air, since it has a certain conductivity due to the presence of the ions .

Therefore, the invention enables an electrospray or electrospinning process for insulating targets and/or depositing material.

Ejecting the material may comprise applying a high enough electric potential such that the material is ejected from the nozzle due to the electrical forces overcoming the surface tension of the liquid, i.e. without applying an additional (mechanical) force. Alternatively or additionally, a force can be applied to eject the material. For example, the nozzle comprises a piston or syringe pump for applying a pressure to expel the material from the nozzle .

In the field of the invention, the nozzle is also known as the emitter. The nozzle may for example comprise a capillary, such as a hollow needle. A capillary promotes the formation of a Taylor cone, from which the material is ejected at a sufficiently high voltage level.

The material will usually be present in a liquid, such as alcohol, tetrahydrofuran (THF), dimehtylformamide (DMF) or an isopropyl alcohol. When the charged droplets or fibres are formed, this solvent will evaporate as the droplets / fibres move away from the nozzle. This results in the creation of charged particles / fibres of the solute material.

The electric potential applied to the nozzle is preferably a high voltage. For example, a voltage over 1 kV, over 10 kV, over 20 kV or over 30 kV is used. The device may include a counter electrode, e.g. for focusing the charged particles. For example, a counter electrode ring may be used. A voltage of the same polarity as the voltage applied to the nozzle is applied to the counter electrode.

The spray chamber is preferably closable. The outlet of the nozzle is located in the chamber. For example, the chamber comprises a door to enable placing the target inside the chamber. Preferably, the chamber is substantially completely closed during use.

Preferably, the walls of the spray chamber are electrically insulating. This prevents the ions from being drawn towards the walls of the chamber. Preferably, in such a case a counter electrode is used for forming the electrospray.

In a preferred embodiment according to the invention, the ions in the spray chamber comprise ions having a polarity opposite to the polarity of the electric potential of the nozzle.

According to the inventors, this contributes to the neutralization of charges on the target, and therefore to the homogeneous building of coating layers on the target.

For example, when the electric potential applied to the nozzle is positive, e.g. +lkV, the ions used are negative ions, e.g. N2~ and 02”.

In a further preferred embodiment, both positive and negative ions are provided.

Experiments show that surprisingly the above effects can also be reached by providing both positive and negative ions to the target.

In a preferred embodiment, the ions are generated by ionizing air.

The ions are for example generated using a corona discharge system. Such a system may comprise a conductor having a sharp edge, e.g. a sharp point, to which a high voltage is applied. The high electric field at the edge ionizes the air which creates a corona discharge. For example, N2~ and 02~ are formed.

Other types of ion sources for use in the method according to the invention include an air ionization device, as conventionally used in air purification devices, and/or a radioactive source.

In a preferred embodiment, the target is electrically insulating. As described above, before the invention it was not possible to coat an electrically insulating target using electrospraying or electrospinning.

Alternatively, the target is electrically conducting.

It is noted that the method of the invention does not require a conducting target to be grounded; it may as well be isolated from ground.

In a preferred embodiment, the target is electrically conducting and electrically connected to ground. The inventors found that although grounding of the target is no longer necessary, it can be advantageous during the start of the coating process. The grounded target efficiently attracts the charged coating material. After the first layer of material has been deposited on the target, the ions will largely take over this role of providing an active surface to attract the coating material.

In an alternative embodiment, the target is electrically conducting and electrically isolated from ground. In conventional electrospray methods isolating the target from ground will lead to back ionization and consequently to the formation of cracks in the coating. By providing ions according to the invention back ionization is prevented.

In a preferred embodiment, the material to be deposited on the target is electrically insulating.

In a preferred embodiment, the method comprises providing the target in an atmosphere comprising the ions.

For example, the target is placed in a holding means, such as a clamp or platform, and the air surrounding the target is ionized by using an ionization device.

In an alternative embodiment, a flow or bundle of ions directed towards the target is created.

In a preferred embodiment, the ions are provided before ejecting the material towards the target. This is especially advantageous in the case of an insulating target, as it allows building up a net charge on the surface of the target by means of the ions before the coating material is applied.

In a preferred embodiment, the material comprises a polymer such that the ejected material forms fibers by means of electrospinning. Preferably, the polymer is chosen such that a nanofiber is created.

In a preferred embodiment, the material comprises a combination of a drug and a polymer. This is in particular advantageous for coating medical devices, such as stents, other implantable devices or catheters. Such invasive devices are often coated with a drug. For example, stents are provided with a coating comprising a drug to prevent restenosis of arteries. Such coatings have to be applied as a very thin layer. Furthermore, the layer has to be as homogeneous as possible. The method according to the invention is in particular suitable in creating such layers. Furthermore, the invention enables applying the coating to non-conducting parts of the medical device as well.

In an exemplary embodiment, the material to be deposited comprises a polymer selected from the group comprising polylactic acid (PLA),poly-L-lactide (PLLA), poly (lactic-co-glycolic acid) (PLGA), thermoplastic polyurethane (TPU), nylon and polyether block amide (PEBA or PEBAX).

In a preferred embodiment, the material comprises a polymer loaded with at least a second material, preferably in the form of nanoparticles. For example, the polymer is loaded with a metal, a ceramic or a precursor, such as chloroplatinic acid. This is in particular useful for the production of batteries.

In a preferred embodiment, the target comprises at least a part of a medical device.

The invention further relates to a medical device obtainable using the method described above. This in particular relates to medical devices comprising parts which are electrically insulating and to which a coating is applied and/or parts to which an electrically insulating coating is applied.

The invention also relates to a device for depositing material on a target, comprising: - an electrospray nozzle for ejecting the material; and - a voltage source connected to the electrospray nozzle for applying an electric potential to the electrospray nozzle; - a spray chamber for placing the target therein; characterized in that the device further comprises - an ion source arranged to provide ions in the spray chamber .

For example, the spray chamber encloses both the target and the outlet end of the nozzle. Preferably, the spray chamber is closable, preferably such that it is substantially completely closed during use. For example, the chamber comprises a door for placing the target inside the chamber .

As described above with respect to the method, the walls of the spray chamber preferably are electrically insulating.

For example, a holding means is provided in the spray chamber for holding the target in the path of the ejected material. The holding means for example comprises a platform or a clamp.

The invention further relates to the use of a device according to the invention for depositing material on at least a part of a medical device.

The same effects and advantages as described in relation to the method according to the invention apply to the medical device, the device for depositing material and the use thereof.

Further details, effects and advantageous of the invention will be explained on the basis of exemplary embodiments of the invention, with reference to the accompanying figures.

- Figure 1 shows schematically a first embodiment of a device according to the invention; and - Figure 2 shows schematically a second embodiment of a device according to the invention.

Device 2 (figure 1) comprises a spray chamber 4. Electrospray nozzle 6 has a needle shaped outlet in spray chamber 4. Nozzle 6 is connected to high voltage power supply 8. In this example, the voltage applied is a positive voltage of 10 kV. Counter electrode ring 9 is positioned inside chamber 4 and connected to a high voltage, which is equal or preferably lower than the voltage of nozzle 6. In this example the voltage level of counter electrode 9 is 5 kV. A stable spray will be developed between nozzle 6 and ring 9.

To push the coating material out of nozzle 6, a syringe 10 is provided.

Two ion generating devices 12, 14 are provided. Ion generating device 12 is connected to high voltage power supply 16 for generating positively charged ions. Ion generating device 14 is connected to high voltage power supply 18 for generating negatively charged ions.

Spray chamber 4 further comprises a support (not shown) on which target 22 is placed. In this example, target 22 is electrically insulating. Optionally, e.g. in the case of a conducting target, target 22 is connected to ground.

To coat target 22, a solvent, e.g. alcohol, comprising the coating material, e.g. a polymer, is provided in syringe 10. Target 22 is placed on the support and spray chamber 4 is closed. Ion generating devices 12, 14 are activated by controlling power supplies 16, 18, such that both positive and negative ions are generated inside the volume of spray chamber 4. Subsequently, power supply 8 is activated, to charge the coating material. Using syringe 10, the material is forced out of nozzle 6 in the form of an electrospray. Counterelectrode ring 9 ensure the formation of a stable spray between nozzle 6 and ring 9. The coating is thereby applied on the surface of target 22.

In a second device 102 (figure 2), a bipolar ionization source 124, i.e. a source creating both positive and negative ions, is provided inside spray chamber 104. Bipolar ionization source 124 is a source as known from air purifier systems. Source 124 is connected to a power supply via cables 126.

To apply a coating to target 122, a solvent comprising the coating material is provided in syringe 110. Target 122 is place on the support (not shown) and spray chamber 104 is closed. Source 124 is switched on, such that ions are generated inside the volume of spray chamber 104. Subsequently, power supply 108 is activated, to charge the coating material. Counter electrode ring 109 is also brought to a high voltage, which is equal to or preferably lower than the voltage level of nozzle 6. Using syringe 110, the material is forced out of nozzle 106 in the form of an electrospray. The coating is thereby applied on the surface of target 122.

The present invention is by no means limited to the above described preferred embodiments thereof. The rights sought are defined by the following claims, within the scope of which many modifications can be envisaged.

CLAUSES

1. Method for depositing material on a target, comprising the steps of: - providing the target in a spray chamber; - providing the material to an electrospray nozzle; - applying an electric potential to the nozzle; and - ejecting the material from the electrospray nozzle towards the target; characterized in that the method further comprises - providing ions in the spray chamber.

2. Method according to clause 1, wherein the ions in the spray chamber comprise ions having a polarity opposite to the polarity of the electric potential of the nozzle.

3. Method according to clause 1 or 2, wherein both positive and negative ions are provided.

4. Method according to clause 1, 2 or 3, wherein the ions are generated by ionizing air.

5. Method according to any of clauses 1-4, wherein the target is electrically insulating.

6. Method according to any of clauses 1-4, wherein the target is electrically conducting and electrically connected to ground.

7. Method according to any of clauses 1-4, wherein the target is electrically conducting and electrically isolated from ground.

8. Method according to any preceding clause, wherein the material to be deposited is electrically insulating.

9. Method according to any of the clauses 1-8, comprising providing the target in an atmosphere comprising the ions.

10. Method according to any of the clauses 1-8, comprising creating a flow or bundle of ions directed towards the target.

11. Method according to any of the preceding clauses, wherein the ions are provided before ejecting the material towards the target.

12. Method according to any of the preceding clauses, wherein the material comprises a polymer such that the ejected material forms fibers by means of electrospinning.

13. Method according to any of the preceding clauses, wherein the material comprises a combination of a drug and a polymer .

14. Method according to any of the preceding clauses, wherein the material comprises a polymer selected from the group comprising PLA, PLLA, PLGA, TPU, Nylon and PEBAX.

15. Method according to any of the preceding clauses, wherein the material comprises a polymer loaded with at least a second material, preferably in the form of nanoparticles .

16. Method according to any of the preceding clauses, wherein the target comprises at least a part of a medical device .

17. Medical device obtainable using the method of clause 16.

18. Device for depositing material on a target, comprising: - an electrospray nozzle for ejecting the material; - a voltage source connected to the electrospray nozzle for applying an electric potential to the electrospray nozzle; and - a spray chamber for placing the target therein; characterized in that the device further comprises - an ion source arranged to provide ions in the spray chamber .

19. Use of the device according to clause 18 for depositing material on at least a part of a medical device.

Claims

Method for applying material to a target, comprising the steps of: - providing the target in a spray chamber; - providing an electrospray sprayer with the material; - applying an electric potential to the sprayer; and - allowing the material to come out of the sprayer in the direction of the target; characterized in that the method further comprises - providing ions in the spray chamber.

Method according to claim 1, the ions in the spray chamber comprising ions with a polarity that is opposite to the polarity of the electric potential of the sprayer.

The method of claim 1 or 2, wherein both positive and negative ions are provided.

The method of claims 1, 2 or 3, wherein the ions are generated by ionizing air.

The method according to at least one of claims 1-4, wherein the target is electrically insulating.

The method of at least one of claims 1-4, wherein the target is electrically conductive and electrically connected to ground.

The method of at least one of claims 1-4, wherein the target is electrically conductive and electrically insulated from ground.

A method according to at least one of the preceding claims, wherein the material to be applied is electrically insulating.

The method of at least one of claims 1-8, comprising providing the target in an atmosphere comprising ions.

A method according to at least one of claims 1-8, comprising creating a stream or bundle of ions in the direction of the target.

The method of at least one of the preceding claims, wherein the ions are provided before the material is sprayed toward the target.

A method according to at least one of the preceding claims, wherein the material comprises a polymer such that the sprayed material forms fibers by means of electrospinning.

A method according to at least one of the preceding claims, wherein the material to be applied comprises a combination of a medicine and a polymer.

A method according to at least one of the preceding claims, wherein the material comprises a polymer selected from the group comprising PLA, PLLA, PLGA, TPU, Nylon and PEBAX.

Method according to at least one of the preceding claims, wherein the material comprises a polymer that is loaded with at least a second material, preferably in the form of nanoparticles.

A method according to at least one of the preceding claims, wherein the target comprises at least a part of a medical device.

A medical device obtainable using the method of claim 16.

Device for applying material to a target, comprising: - an electrospray sprayer for spraying the material; - a voltage source connected to the electrospray sprayer for applying an electrical potential to the electrospray sprayer; and - a spray chamber for placing the target therein; characterized in that the device further comprises: an ion source adapted to provide ions in the spray chamber.

Use of the device according to claim 18 for applying material to at least a part of a medical device.