Device for coating a stent and associated coating method and stent produced according to the method

Abstract

A device for coating a stent, including a holder for the stent, a spraying unit comprising a spray mandrel and an air nozzle. The spray mandrel, the air nozzle and the holder are configured and disposed relative to each other such that the spray mandrel projects from one side into the stent during coating and the air nozzle projects into the stent from the opposing side. A method for coating a stent employs the device. Stents that can be obtained according to the method.

Claims

1. A method for coating a stent, comprising the following steps: a) holding the stent in a holder that is part of a device including a spraying unit with a spray mandrel and an air nozzle, wherein the spray mandrel, the air nozzle and the holder are configured and disposed relative to each other such that the spray mandrel projects into the stent from one side during coating and the air nozzle projects into the stent from the opposing side, and wherein the stent can be moved in the direction of the spray mandrel or in the direction of the air nozzle during coating, and wherein the spraying unit further comprises a spray nozzle that is directed at an abluminal side of the stent; b) coating the luminal side of the stent by introducing a mandrel spray jet via the spray mandrel and an air flow via the air nozzle such that the spray jet is deflected radially outwardly by the air flow in a counterflow region; c) displacing a position of the counterflow region relative to the stent by at least one of the measures selected from moving the stent, moving the spray mandrel, moving the air nozzle, regulating the mandrel spray jet, and regulating the air flow; and d) while carrying out steps b) and c), a nozzle spray jet of the spray nozzle is directed at the counterflow region at the outside of the stent, wherein in the interior of the stent an air flow is generated by the air nozzle and the mandrel spray jet is simultaneously generated by the spray mandrel.

2. The method according to claim 1, wherein the luminal and abluminal sides are coated with differing active agents.

3. The method according to claim 2, wherein a healing-promoting active agent is applied to the luminal side.

4. The method according to claim 3, wherein the healing-promoting active agent is atorvastatin.

5. The method according to claim 2, wherein a proliferation-inhibiting active agent is applied to the abluminal side.

6. The method according to claim 5, wherein the proliferation-inhibiting active agent is sirolimus or a derivative thereof.

7. A method according to any one of claim 2, wherein the active agents are embedded in a carrier matrix.

8. The method according to claim 7, wherein the carrier matrix is biocorrodible.

9. The method according to claim 8, wherein the carrier matrix comprises PLLA.

10. A method for coating a stent, comprising the following steps: directing an axial spray jet with luminal coating material into the lumen of the stent; directing an opposite axial air flow into the lumen of the stent to meet the axial spray jet and create a counterflow region that redirects the axial spray jet radially outward to coat a luminal surface of the stent; simultaneously directing an abluminal spray jet with abluminal coating material to coat an abluminal surface of the stent, wherein the abluminal spray jet is aligned with the counterflow region to inhibit abluminal coating material from entering the lumen of the stent, and moving the counterflow region relative to the stent while maintaining alignment of the abluminal spray jet with the counterflow region.

11. The method of claim 10, further comprising creating an overpressure in the lumen of the stent.

12. The method of claim 10, wherein the luminal coating comprises a different active agent than the abluminal coating.

13. The method of claim 12, wherein the luminal coating comprises atorvastatin and the abluminal coating comprises sirolimus.

14. The method of claim 10, wherein the composition of the abluminal coating is adjusted during the moving.

15. The method of claim 10, wherein the duration of moving is varied to vary the thickness of the abluminal and luminal coatings in different peripheral sections of the stent.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic illustration of the device according to the invention for coating the luminal side of the stent;

(2) FIG. 2 is a schematic illustration of the device according to the invention for coating the abluminal side of the stent;

(3) FIG. 3 is a schematic illustration of a transversally cut implant cross-section having a luminal and an abluminal layer thickness after sequentially combining separate inside and outside coatings;

(4) FIG. 4 is a layer thickness evaluation for the outside coatings of implant cross-sections in four transversal cutting planes for analysis of the longitudinal layer thickness consistency; and

(5) FIG. 5 is a layer thickness evaluation for the inside coatings of implant cross-sections in four transversal cutting planes for analysis of the longitudinal layer thickness consistency.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) The invention is based on the realization that luminal and/or abluminal coatings can be achieved in a very simple and reliable manner using a spraying method in which a counterflow is generated by an air nozzle. For this purpose, the device includes a spraying unit having a spray mandrel, the outside diameter of which is smaller than the inside diameter of the stent. Moreover, an air nozzle is present, the outside diameter of which likewise is smaller than the inside diameter of the stent. During the coating process, the stent is accommodated by a holder such that the lateral openings of the stent are accessible and the lateral walls are not shielded. The spray mandrel is then inserted into the stent from one side and the air nozzle from the opposing side. During the coating process, a spray jet is generated by the spray mandrel and an air flow is directed at this spray jet by the air nozzle. In the region where the spray jet and air flow meet (which here is referred to as the counterflow region), the spray jet is deflected radially outwardly and thus coats the luminal surface of the stent in this region. Using different measures, it is now possible to vary the counterflow region relative to the position of the stent, whereby locally differentiated luminal coating of the stent is possible. These measures include moving the stent, the spray mandrel or the air nozzle and regulating the spray jet and air flow. The coating method according to the invention results in a form-fitting, mechanically very stable coating.

(7) The device is preferably configured such that the position of the stent relative to the spray mandrel and the air nozzle can be varied during coating. The holder is notably configured such that, during coating, the stent can be moved in the direction of the spray mandrel or in the direction of the air nozzle. In other words, according to this variant the stent is moved along an axis formed by the spray mandrel and air nozzle via the holder during the coating process. The adjustments of the position and flow rate in the counterflow region can be determined in this region particularly easily by experiments and simplify the implementation of the method in the industrial manufacturing process.

(8) It is further preferred for the spraying unit to include a spray nozzle, which is directed at an abluminal side of the stent. According to an associated variant of the method, in step a) a device for coating the stent is provided, in which the spraying unit includes such a spray nozzle, which is directed at an abluminal side of the stent. The abluminal coating can be carried out simultaneously with the aforementioned luminal coating (ii), before that (i) or (iii) thereafter. For simultaneously coating the abluminal side of the stent, a spray jet of the spray nozzle is directed at the counterflow region while steps b) and c) are carried out. Abluminal coating, however, can also be carried out before or after the luminal coating process, wherein a spray jet is directed at the outside of the stent. The quantity of coating material inadvertently reaching the luminal surface can optionally be reduced by an air flow from the air nozzle, or by a counterflow region, which is generated with an air nozzle and a spray mandrel that is operated without active agent.

(9) In keeping with the aforementioned descriptions, according to this variant the spraying unit of the device according to the invention includes an additional spray nozzle, which is directed at the outside of the stent. Over the course of the abluminal coating step, the flow that is radially directed outwardly in the counterflow region can largely prevent coating material for the abluminal coating step from entering the interior of the stent. As an alternative or in addition, overpressure is generated in the interior of the stent with the spray mandrel or the air nozzle, this overpressure being intended to prevent penetration of the spray jet generated by the spray nozzle or to discharge penetrating material laterally.

(10) During the abluminal coating step, the spray jet generated by the spray mandrel does not have to contain any carrier material or active agent, unless minor mixing is desirable for abluminal coating. The compositions of the coatings on the luminal and abluminal sides of the stent are generally different from each other, which is to say they include differing carrier materials and/or differing active agents. For example, growth-inhibiting active agents are preferably deposited on the abluminal upper face of the stent, while healing-promoting substances are applied to the luminal surface. The luminal and abluminal sides are preferably coated with differing active agents. In particular, atorvastatin is applied luminally and sirolimus is applied abluminally.

(11) The active agents can notably be embedded in a carrier matrix. The carrier matrix can be biocorrodible and preferably includes PLLA.

(12) A further aspect of the invention relates to a stent, which is produced according to the aforementioned method.

(13) FIG. 1 schematically shows the principle of coating the luminal side of a stent 10 using the device according to the invention. For this purpose, the device includes a holder 12, which is used to accommodate the stent 10 during the coating process. The holder 12 is configured to perform a translatory movement by actuators, which are not shown in detail here.

(14) The device further includes a spraying unit 20 having a spray mandrel 22. A spray jet 24 consisting of the coating material and a suitable carrier is generated by the spraying unit 20. The spray jet 24 is conducted into the interior of the stent 10 via the spray mandrel 22.

(15) An air nozzle 30, which generates an air flow 32, is located on the opposite side of the stent.

(16) The spray jet 24 and the air flow 32 meet in a counterflow region 40 and the spray jet 24which is now mixed with the air flow 32is accordingly directed radially outwardly and there impinges on the luminal surface of the stent 10 to be coated. A portion of this radially outwardly directed mixed flow 42 also enters through the openings of the filigree support structure of the stent 10.

(17) So as to vary the location of the luminal coating, the holder 12 is moved along the axis formed by the spray mandrel 22 and air nozzle 30. The relative position of the counterflow region 40 to the stent 10 changes accordingly. In a certain luminal section of the stent 10, the composition of the luminal coating can be adjusted by varying the composition of the spray jet 24. The layer thickness can be influenced by the duration of the coating process and the coating composition in any arbitrary peripheral section of the luminal surface of the stent 10.

(18) FIG. 2 is intended to illustrate a variant of the coating device in which the spraying unit includes an additional spray nozzle 52, which is used to coat the outside of the stent 10. A spray jet 54 is conducted over the stent 10 during the abluminal coating step by the spray nozzle 52. An overpressure, which effects an air flow that is directed radially outwardly through the filigree structures of the stent 10, can be generated in the interior of the stent 10 by the spray mandrel 22 and the air nozzle 30, which is not shown here. This air flow is adjusted so as to prevent penetration of the spray jet 54, while still allowing the abluminal surface of the stent 10 to be coated. Likewise, undesirable deposition of the abluminal layer material on the luminal surface can be reduced by way of an air flow that is generated by the air nozzle or spray mandrel.

(19) Using the aforementioned device, a stent is first provided on the luminal side with a coating made of atorvastatin in PLLA and then on the abluminal side with a coating made of sirolimus in PLLA. The coating thickness on the inside of the stent should be approximately two to three times the coating thickness on the outside.

(20) FIG. 3 is a schematic illustration of a transversally cut implant cross-section having a luminal and an abluminal layer thickness after carrying out the sequential combination of separate inside and outside coatings.

(21) The centers of the illustrations show the cross-section of a stent strut (1). The surface of the strut is surrounded by an inner layer (4, 6), wherein the luminal layer thickness (4) is considerably greater than the abluminal one (6). The abluminal layer thickness (6) is nonetheless greater than zero, resulting for the inner layer (4, 6) in both considerable accumulation on the luminal surface and in a form fit that increases the mechanical stability of the inner layer. The outer layer (5, 7) likewise exhibits form fit, wherein the abluminal layer thickness (7) is slightly less than the luminal one (5).

(22) FIG. 4 shows a layer thickness evaluation for an outside coating and FIG. 5 shows a layer thickness evaluation for an inside coating of implant cross-sections in four transversal cutting planes for analyzing the longitudinal layer thickness consistency and the luminal/abluminal coating selectivity. Shown in light gray in FIG. 4 is the layer thickness of the layer material deposited on the abluminal implant surface, and shown in dark gray is the layer thickness of the layer material deposited on the luminal implant surface. Shown in light gray in FIG. 5 is the layer thickness of the layer material deposited on the luminal implant surface, and shown in dark gray is the layer thickness of the layer material deposited on the abluminal implant surface.

(23) It will be apparent to those skilled in the art that numerous modifications and variations of the described examples and embodiments are possible in light of the above teaching. The disclosed examples and embodiments are presented for purposes of illustration only. Other alternate embodiments may include some or all of the features disclosed herein. Therefore, it is the intent to cover all such modifications and alternate embodiments as may come within the true scope of this invention.