JP2007512107A - Differential coating and coating method - Google Patents

Abstract

The present invention, in an exemplary embodiment, provides a stent that combines many of the superior properties of both silicone and metal stents while eliminating undesirable properties. In particular, the main objective according to the present invention is to make the relative hardness / softness of one area of the stent different from the relative hardness / softness of the other areas of the stent to further increase patient comfort and compression force. It is to provide a group of stents that can provide resistance. Exemplary embodiments provide a stent that is coated to provide a predetermined property. In particular, a coated stent is provided that is coated from the inside so that the outer surface of the stent framework structure has an increased friction point while the inner surface exhibits predetermined properties.

Description

  The present invention relates to a method for coating and / or coating a medical device, and more particularly, a method for adjusting the followability of a coating to change the fluid dynamics inside the medical device and the friction point outside the medical device. About.

  A stent is a device that is inserted into a tube or point of communication to open and hold a lumen and prevent occlusion due to stenosis, external compression, or internal obstruction. Specifically, stents are commonly used to open and hold blood vessels in coronary arteries, and stents can be inserted into the ureter to maintain urination from the kidney, and can be used for pancreatic cancer or bile ducts. It is often inserted into the bile duct for cancer, or inserted into the esophagus for stenosis or cancer. Although stent placement in blood vessels as well as in non-vascular lumens has evolved significantly, unfortunately significant limitations remain with respect to techniques for making stents suitable for various portions of a patient's anatomy.

  Historically, to provide a stent with a variety of properties, the stent had to be made from a number of materials, with at least one material corresponding to each desired property. As a result, many of these stents are woven, for example, from two or more metals having different shape memories. Unfortunately, however, braided stents are subject to premature aging. In addition, as multiple materials are included in a single stent, discontinuous properties may occur along the surface area of the stent. This is particularly undesirable when the stent is placed in a vessel or non-vessel lumen that is already occluded for one reason or the other. Stents need to be more rigid in some areas, but need to be more flexible in other areas.

  In addition, medical device companies have identified the need to at least partially cover the stent to prevent epithelialization in the structure. However, most covered stents have an elastomeric cover that is prone to wrinkles, particularly in the vicinity of stenotic tissue. This can lead to additional tissue granulation. Further, when the stent is dip coated, the coating may be non-uniform or the performance of the stent may be inconsistent from batch to batch.

  In addition, the ends of the stent tend to be exposed to promote the formation of granulation tissue that helps to place the stent in place. In the case of a metal stent, the direct contact between the metal and the tissue promotes tissue granulation and galvanic current is also generated as an undesirable by-product. Such currents have an indirect effect on tissue granulation and may directly affect the fluid flow mechanism.

  In addition, many medical device companies are trying to use cardiovascular stents that are not well suited to the pulmonary, gastrointestinal, and peripheral vascular manifestations, so that anatomically different locations in the lumen Many are not considered in stent design. For example, the cardiovascular pulsation and associated radial force requirements of cardiovascular stents are very different from the tightly contracting lumen requirements of the trachea during repeated coughing. When a stent developed for the former is applied to the latter, the stent becomes useless under severe conditions and tends to lose its elasticity and hence the ability to ensure airway patency. Lumens other than blood vessels also tend to have ciliated epithelium to facilitate removal of fluids and particulate matter. As a general principle, if the coated stent is not specifically designed for ciliated lumens, the outer coating will damage the cilia and prevent the body's natural removal function. Furthermore, the coating itself is usually preferentially made from a hydrophilic polymer, which may result in mucus formation and / or fluid stagnation. Stagnation of fluid or material through the lumen can cause additional complications such as stent restenosis or microbial infection.

  Therefore, there is a current need for a therapeutic stent that can be configured from a single substrate by die cutting, without braiding, but having various properties along its surface area. Further, there is a need for a treatment stent in which the relative hardness, softness, flexibility, stiffness, and radial force can be altered as a function of deployment considerations rather than material considerations. Yes. In particular, it can be divided into multiple regions, with certain characteristics in one region and significantly different characteristics in adjacent regions, typically anatomical lumens, specifically individual patients There is a need for a stent that can be adapted to a particular lumen profile. In addition, there is a need for a method that individually changes the position, followability, and density of the cover to achieve the desired behavior. In particular, there is a need for a coated stent that is coated from the inside so that the outer surface of the stent framework is lifted from the outer surface of the coating. According to this, the function of the cilia need only be partially limited, and the mucociliary removal action is not severely adversely affected. It is also a coating that itself has anti-adhesive properties or forms a complex with an anti-adhesive agent, and in a broad sense, a stent, specifically a coating, by bacteria, fungi, or other microorganisms. However, there is also a need for a coating that prevents it from being attacked. There is also a need for a cover for the proximal and distal ends of a stent that has the features of a conventional uncoated stent but can prevent epithelialization and granulation tissue formation.

  The main object of the present invention is to provide a stent according to an exemplary embodiment of the present invention that combines many of the superior properties of both silicone and metal stents while eliminating undesirable properties. In particular, it is an object of a preferred embodiment according to the present invention to provide an easily installed stent and, in an alternative embodiment, a removable stent. Furthermore, it is desirable that the stent according to this embodiment of the present invention can reduce infection without causing infection of the material. Accordingly, it is a primary object of a preferred embodiment according to the present invention to provide a prosthesis that is suitable for both permanent and temporary use and that is easy to insert, reposition and remove.

  The main objective of a preferred embodiment of the present invention is to provide a stent that is preferably die-cut from a single material and can maintain its axial effective length when compressed radially. There is to do. To achieve this goal, the stent does not have a seam that can worsen the luminal tissue. In particular, the stent according to the present invention is formed using a tool for shaping the outer shape of the stent and its gap.

  Yet another object of an exemplary embodiment of the present invention is to provide a stent that is adapted for the treatment of benign and malignant diseases and that allows physicians to improve the way malignant obstructions are treated.

  Still another object of the present invention is to provide a stent and method for installing the stent that is economical and suitable for routine purposes. In addition, the stent has minimal misalignment, minimal granulation, does not shorten after expansion, and the removal action by mucociliary will not be a problem.

  Yet another object of an exemplary embodiment according to the present invention is to be used for pediatric and adult patients with excellent inner / outer diameter ratio, radial force with excellent dynamic expansion and having malignant and benign diseases. It is to provide a prosthesis suitable for being made.

  The main purpose of an exemplary stent according to the present invention is to make the relative hardness / softness of one area of the stent different from the relative hardness / softness of the other areas of the stent to provide additional patient comfort and radius. It is to provide a group of stents that can provide resistance to directional forces.

  A further object in accordance with exemplary embodiments is to provide a group of stents having a novel gap configuration that facilitates flexibility, durability, and / or proper placement.

  Yet another object of a preferred embodiment of the present invention is a self-expanding having the above advantages that also define a plurality of openings along the skeletal structure at or between the ends of the stent, particularly for stent removal. It is to provide a stent. To achieve this and other objectives, the suture may be threaded through one or more of these openings, for example, to facilitate tightening for removal of the device.

  A further object according to a preferred embodiment of the present invention is to provide a prosthesis that minimizes cilia breakage at the implantation site as much as possible. To facilitate this and other purposes, the preferred prosthesis is that the surface of the strut that contacts the patient's lumen is lifted above the surface of the capsule, thereby allowing the cilia to move and free the cilia-bearing epithelium. It is coated from the inside with polyurethane so as to allow a fluid action.

  Yet another object of the present invention is to provide a cover and a method for applying the coating to a stent. This coating may be applied to have various levels of followability to the stent struts. This results in conditions that adjust the hydrodynamics of the inner diameter of the stent and the friction point of the outer diameter of the stent.

  Yet another object in accordance with the present invention is to provide a coating around the distal end, proximal end, or both so as to maintain the gain of the uncoated stent while maintaining the ability to remove the stent. is there. Furthermore, in addition to the coating for eliminating the galvanic current, a coating of only the end portion and a coating of the entire stent may be provided.

  Still other objects, features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.

  A preferred embodiment of the stent according to the present invention provides a stent that prevents stent epithelialization and can be engaged at a desired implantation site without premature expansion and contraction. Also, the stent retains its axial length when subjected to radial compression.

  The stent is preferably formed of a composite material selected from the group consisting essentially of Ni, C, Co, Cu, Cr, H, Fe, Nb, O, Ti and combinations thereof. The composite material is generally formed into a compression tube, from which the stent is etched and formed on a suitable molding device to give the stent the desired outer shape. Both synthetic collar technology and in vitro evaluation technology allow the stent according to the present invention to convert the acting force into a deforming action that is absorbed by the cornered structure, thereby causing excessive structural stresses. It has been shown to have a remarkable ability to prevent premature material fatigue as well as aging.

  A person skilled in the art of stent engineering will be able to manufacture stents consistent with the present invention by other methods upon notification of the present application. Preferred methods for manufacturing such stents are as follows. is there. As described above, a composite material is selected and a workpiece is formed. The workpiece is preferably laser etched, and the etched workpiece is generally verified for accuracy using video recording microscopy. Dimensional measurements are taken to ensure strut thickness, segment angle, zone placement, etc. Also, the stent is preferably formed on a forming tool that has substantially the desired outer shape of the outer dimensions of the stent.

  If the stent is shaped to a specific lumen size, optical and / or video imaging of the target lumen may be performed prior to stent formation. The corresponding zone and connection region geometry of the stent can then be etched away according to the requirements of the target lumen. For example, if the stent is designed for trachea and has a generally D-shaped lumen and the intermediate zone needs to be more flexible than the end zone, the stent can be designed to that specification. In particular, a patient-specific prosthesis can be designed if the shape of a particular patient's trachea is optically captured and given the appropriate dimensions. These techniques are adaptable to other non-vascular lumens, but are very well suited for vascular applications where patient-specific shapes depend on various factors such as genetic characteristics and lifestyle.

  It should be noted that, unlike using different shape memory materials to change the area of the stent, the stent according to the present invention can obtain countless combinations of properties. Because of modification of multiple zones and multiple segments within one zone by changing the angle, segment length, and segment thickness during the etch and molding phases or post-molding and polishing phases in stent technology Because you can. Moreover, an additional function can be obtained by correcting the shape of the connection part between zones.

  An exemplary stent according to the present invention is shown in FIGS. These figures show a preferred interstice geometry. Various other acceptable gap shapes other than this preferred shape are not shown, but there are U, V, W, Z, S, and X shapes to name a few.

  The stent is also formed from a shape memory alloy and preferably has a unique geometric gap that is laser etched. However, other conventional methods of forming a gap in a single stent are considered not equivalent, but can be used within the scope of those skilled in the art.

  However, this does not mean that the knowledge that changes in gap geometry affect stent function is currently known in the art. This cannot be overemphasized no matter how you emphasize it. Conversely, the inventors have found a correlation between gap geometry, width, length and relative resistance to torsional stress and radial forces. In practice, the stent has a circumferential zone extending perpendicular to the longitudinal axis of the luminal device. These bands are generally called zones. A connector connects these bands to each other, and the connection is an additional means for adjusting the stent function. Specifically, the connection portion defines a substantially U-shaped member, but other examples such as U, V, W, Z, S, and X-shapes, to name a few, A geometric shape can also be defined. A plurality of thread holes are also provided to allow the physician to pass the suture through the stent for ease of removal. These thread holes are preferably between about 200 μm and 300 μm, but may be smaller or larger than these values to suit the needs of the target site. When the preferred suture is 4-0, the preferred thread hole size is about 350 μm. The medical device may be pre-threaded, or the user may supply the suture after implantation.

  Exemplary stents according to the present invention with relatively high twist and radial flexibility are considered soft. An exemplary stent that is evaluated as soft has a distance between U-shaped connections of approximately 4.5 μm in a compressed state (ie, contracted to a 3 mm tube that has been laser etched). The length of the crossing member is preferably about 1.0 μm, and the length of the leg member is preferably about 1.5 μm. The leg member may further comprise feet provided on the remaining portion of the stent framework. The foot can be adjusted from a standard length of about 0.25 μm to further adjust the properties of the stent. In addition, a substantially rectangular member with similar ability to variation is incorporated into the U-shaped connection. The variation factor and the result of changing the dimension of the substantially rectangular member are the same as those revealed by changing the length dimension of the leg member.

  As an example, but should not be construed as limiting in any way, the flexibility index or relative flexibility can be increased by increasing the various lengths described above. For example, the flexibility is increased by increasing the length of the leg member and the cross member of the U-shaped connecting portion. However, in a preferred embodiment of the stent, there is an inverse correlation between length and flexibility with respect to the distance between U-shaped members and the distance between gaps. This relative softness / hardness index as a result of the gap size is a novel aspect of the preferred embodiment of the present invention. As a practical experience, joining long leg members at an acute angle increases flexibility. On the contrary, if the length of the leg portion is shortened and coupled to an obtuse angle, the rigidity increases. As a non-limiting example, a U-shaped connection where the short leg member bends from the cross member at an angle greater than 90 °, the long leg member branches off from the cross member at an angle less than 90 °. Compared with a U-shaped connection portion, the rigidity is extremely high and the resistance to torsional stress is extremely large.

  In addition to length and spacing differences, the gaps may define various shapes that, depending on their very nature, give the stent a new functionality. However, the change in functionality is not a function of the shape itself, but rather a function of dimensional differences between the various shapes. It is therefore important to note that the dimensional differences mentioned in the previous paragraph determine the function imparted to the stent by various gap shapes. Thus, after being informed of the present invention, those skilled in the art can come up with a number of gap shapes and meet specific functional criteria by keeping certain dimensional parameters constant.

  1-3 also show the coating provided in an alternative embodiment according to the present invention. The coating is preferably made of a stable polymer material such as polyurethane that can be deposited on the stent to form a thin film. When the thin film is welded to the stent, the layer is preferably formed so that the hydrophobic portion in the polymer is mainly directed outward and the hydrophilic portion is mainly directed inward. It should be noted that the relative hydrophilicity may be changed depending on the properties desired by the user. For example, if the implant is placed in a respiratory system with the intention of collecting mucus, it is more appropriate that the coating is mainly hydrophobic on the outer surface. In addition, by adjusting the hydrophilicity of the coating, physicochemical parameters such as surface free energy and charge density are generally mediated by biofilm formation and microbial adhesion and extracellular polymers. Provides a substantial barrier to the binding phenomenon. However, additional anti-adhesives known in the art may be applied to provide lubricity as well as an additional barrier to microorganisms. For example, preferred coatings according to the present invention may be hydrophilic and hygroscopic to ensure that the surface is constantly moistened and mucus stagnation as well as microbial adherence is prevented.

  Regardless of the desired coated surface properties, preferred stents according to the present invention are coated from within the lumen of the framework structure. The cover is deliberately in the form of a thin film that follows the strut shape, a thin film that does not follow the strut shape and is positioned on the inner diameter of the stent, or an intermediate thin film that approaches the strut. It should be attached. One of the main functions of the adjustable coating method is to increase the friction point outside the stent and / or to control the flow characteristics inside the lumen of the stent.

  With particular reference to FIGS. 1 and 3, the stent strut 100 is shown with the inner surface 120 of the lumen facing up. When the stent strut 100 is coated from the inner surface 120 side, the compliant cover forms a step between the struts 100, thereby providing fluid retention. If this is a desirable property based on the lumen that the stent is intended for, such coating can be achieved by using a compliant heating device in joining the cover 200 to the struts. Conversely, as shown in FIGS. 2 and 5, if a relatively smooth inner diameter is desired, the cover 200 may be configured so that it does not follow the contour of the stent strut 100 using a non-following device. 100 is attached.

  Referring to FIG. 4, the cover 200 is provided on the inner surface 120 of the stent. However, the cover 200 may require extremely high followability such that it extends through the gap toward the outer surface 140. By adjusting the followability of the cover between such extreme examples, the degree of friction and flow based on the desired design evaluation can be optimized.

  The stent is preferably coated by a multi-stage process that includes providing the stent and spraying the stent with a polymeric material to coat the struts. These steps may be reversed, but it is preferable to follow the step of coating the inside by spraying. For certain stents, the inner diameter of the stent is covered with a polymeric material to form a non-porous cover 200 with the stent placed in a hollow mold and retaining the shape of the stent. Alternatively, a porous cover may be used to impart breathability or selective permeability to the cover. The cover 200 can be provided in the form of a sheet or by additional spraying, although the preferred embodiment is in the form of a sheet. Sheets are preferred because they generally facilitate proper orientation of the polymer side chains and ensure that the desired portion (eg, hydrophilic and / or hydrophobic) can be placed facing the lumen. After the polymer layer is introduced into the stent inner diameter, a temperature controllable balloon or other processing device is introduced with the polymer layer sandwiched between the stent inner diameter and the balloon. The balloon is inflated and heated to a temperature of about 200 ° F. (93 ° C.) to 400 ° F. (204 ° C.) to anchor the polymer to the stent. Although preferred polymers such as various polyurethane products (eg Chronoflex® manufactured by Cardiotech International) are suitable for such applications, other polymers may be used. The degree of compatibility depends on the followability of the balloon and the presence or absence of a collar around the outer surface of the stent. The collar may have ribs or concave walls that complement the stent gap in order to easily obtain very high followability of the cover.

  In addition, the same method may be used to coat or coat a portion of the stent rather than covering the entire stent. In particular, smaller pieces of covering material may be applied to the distal and proximal ends of the stent to prevent excess granulation material. Such stents are useful in cases such as phototherapy and lung transplants where uncoated metal stents are commonly used.

  The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The embodiments described herein are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.

FIG. 3 is a perspective view of a cross section of an optional stent selective strut having a cover applied to the inner diameter to fit the stent strut. FIG. 2 is an alternative perspective view of a cross section of the selective stent strut of FIG. 1 with the cover not following the stent strut. FIG. 2 is an enlarged perspective view of the stent, looking at the lumen from one end, showing the compliant cover of FIG. 1. FIG. 6 is an alternative perspective view of one end of the stent that is highly dependent so that the cover extends through the gap toward the outer surface of the stent in an area of the stent. FIG. 5 is an enlarged perspective view of a post whose cover does not match the post geometry.

Claims (28)

A medical device for placement within a patient's anatomy,
A generally cylindrical member having a distal end and a proximal end and extending longitudinally therebetween and having a lumen formed therethrough. The framework structure is configured to define a plurality of struts having an inner surface and an outer surface extending along a longitudinal direction and forming a geometric pattern formed by a plurality of corners. ,
In order for the instrument to conform to the shape of the intended lumen and so that the instrument does not cause undesired shortening or stretching when pressure is applied along each longitudinally extending point of the instrument, A medical device wherein the corners determine the relative flexibility of the device.   The framework structure further comprises a coating coupled to the framework structure so that both the struts and the region between the struts are coated, the coating having a thickness sufficient to prevent galvanic current. The medical device according to claim 1.   The medical device according to claim 2, wherein a part of the framework structure is covered with a polymer material.   The medical device according to claim 3, wherein only each of the ends of the framework structure is covered.   The medical device according to claim 3, wherein the coating is applied to the lumen.   The medical device according to claim 5, wherein the coating is substantially hydrophobic.   The medical device according to claim 5, wherein the coating is substantially hydrophilic.   The medical device according to claim 6, wherein the coating is substantially hygroscopic.   The medical device according to claim 7, wherein the coating is substantially hygroscopic.   The medical device of claim 1, wherein at least one of the struts is defined with an opening extending through the strut.   11. The medical device of claim 10, wherein the at least one opening defines a thread hole having a diameter through which a suture can be inserted.   The medical device according to claim 11, wherein the diameter of the thread hole is at least 300 μm.   The medical device according to claim 5, wherein the coating is configured not to prevent bending or radial expansion of the framework structure.   14. The medical device of claim 13, wherein the coating is fully attached to the outer surface of the stent strut.   The medical device according to claim 14, wherein the coating is not attached to an outer surface of the stent strut.   The medical device according to claim 1, wherein the torsional rigidity is determined by a dimension of a geometric shape of the frame structure.   The medical device according to claim 1, wherein the frame structure is formed of a shape memory alloy.   The medical device according to claim 17, wherein the framework structure is electropolished.   The medical device according to claim 1, further comprising a plurality of flanges defining an opening extending therethrough along a longitudinal extension of the framework structure.   The medical device according to claim 1, further comprising a connecting portion that connects the geometric pattern portions, wherein the connecting portion includes a cross member and a plurality of leg members extending from the cross member.   21. The medical device of claim 20, wherein the connecting portion further comprises a rectangular detent extending from its leg.   21. The medical device of claim 20, wherein the length of the leg member and the magnitude of the angle at which the leg extends from the cross member determines the relative flexibility of the medical device.   The medical device according to claim 21, wherein an angle at which the leg member extends from the cross member is greater than 90 degrees.   24. The medical device of claim 23, wherein the framework structure is relatively hard.   24. The medical device of claim 23, wherein an angle at which the leg member extends from the cross member is less than 90 degrees.   The medical device according to claim 24, wherein the framework structure is relatively soft. Providing a mold having an inner diameter and an outer diameter;
Providing a skeletal structure, the skeleton structure having a distal end and a proximal end, extending longitudinally therebetween and formed with a lumen therethrough; The frame structure is configured to define a substantially cylindrical member, and the frame structure has an inner surface and an outer surface extending along a longitudinal direction, and forms a geometric pattern formed by a plurality of corners. A plurality of struts, wherein the instrument conforms to the shape of the intended lumen, and the instrument is undesirably shortened or stretched when pressure is applied along each point extending in the longitudinal direction of the instrument The relative flexibility of the instrument is determined by the corners so as not to cause
Inserting the framework structure into the inner diameter of the mold;
Attaching a polymer material to the inner surface of the framework structure;
Applying a heat to the polymer material to fix the polymer material to the framework structure.   28. The method of claim 27, further comprising attaching a polymeric material to an outer surface of the framework structure.

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