Multi-layered radiopaque coating on intravascular devices

Abstract

Intravascular devices having a radiopaque layer thereon for visualization are provided. The devices further includes a capping layer on the radiopaque layer to prevent exposure of the radiopaque material to surrounding tissues. A method of coating the device is also provided. The method includes using an unbalanced magnetic field magnetron to generate, from a source, metal atoms for coating and bombarding ions for compressing deposited metal atoms to the surface of the device.

Description

RELATED U.S. APPLICATIONS(S) [0001] This application claims priority to U.S. Provisional Application Ser. Nos. 60 / 252,005, filed Nov. 20, 2000, and 60 / 253,107, filed Nov. 27, 2000, both which are hereby incorporated herein by reference.FIELD OF THE INVENTION [0002] The present invention relates to intravascular devices, and in particular, to intravascular devices having radiopaque coatings thereon for visualization. BACKGROUND ART [0003] Many medical intravascular devices are used either temporarily or permanently inside the human body. An example of such an intravascular device includes a stent for use in, for instance, coronary angioplasty. Stents are small metal scaffolds used to mechanically hold open and support constricted coronary arteries. For proper positioning, stents may need to be visualized during and after deployment using imaging techniques such as x-ray radiography and x-ray fluoroscopy. However, due to the nature of the materials used to construct these intravascula...

AI Technical Summary

Benefits of technology

The present invention provides an intravascular device with a layer of radiopaque material for visualization and a capping layer to prevent exposure to surrounding tissue. A transition layer may be added between the layer of radiopaque material and the capping layer to enhance bonding. An adhesion layer may be added to promote bonding of the layer of radiopaque material to the substrate. The invention also provides a method for coating the device by generating a flux of atoms of radiopaque material and a flux of bombarding ions in a co-linear fashion and depositing the atoms onto the substrate surface while impacting them with the bombarding ions to provide a uniform layer. A capping layer may also be added.

Problems solved by technology

However, due to the nature of the materials used to construct these intravascular devices and their small size, visualization of these devices can often be poor or non-existent.

However, incorporation of these radiopaque materials, including ones that are biocompatible, into the device substrate material can have an undesirable effect on other device characteristics, such as mechanical performance.

However, bands have the potential for becoming loose, shifting, or even falling off.

Moreover, bands may also cause abrasion to the intima (i.e., the lining of a vessel wall) during insertion of the device, especially if the bands have sharp edges or outward projections.

Additionally, cellular debris can be trapped between the intravascular device and the band, and the edges of the band can serve as a site for thrombus formation.

However, for the range of thickness required to make the coating x-ray opaque, CVD and conventional PVD methods do not appear to provide a coating which can exhibit sufficient adhesion to the surface of the device, especially a stainless steel substrate surface, to be reliable in a medical device application.

On the other hand, electroless and / or electroplated coatings are often porous, and can present a biocompatibility problem, since the porous coating can act to entrap the plating chemicals.

For devices constructed from, for instance, titanium alloys, embrittlement caused by the electroplating process can occur to significantly alter the mechanical properties and thus the function of the device.

Coatings produced by traditional IBAD, however, are costly.

When evaporating, atoms of expensive noble metal are emitted over a large solid angle compared to that subtended by the device or devices being coated, thus requiring a costly reclaiming process.

Moreover, because an evaporator uses a molten metal, it must be located upright on the floor of the deposition chamber to avoid spilling, thereby restricting the size and configuration of the chamber and the devices being coated.

Additionally, evaporators cannot deposit mixtures of alloys effectively because of the differences in the alloy components' evaporation rates.

As a result, the growth mechanism of the coating can be inconsistent, and uniform coating properties are difficult to achieve even over the same device.

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