Stock material or miscellaneous articles – Surface property or characteristic of web – sheet or block
Reexamination Certificate
2000-12-21
2003-09-02
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Surface property or characteristic of web, sheet or block
C427S002240, C427S539000, C428S457000, C428S469000, C428S544000, C428S685000
Reexamination Certificate
active
06613432
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention (Technical Field)
This invention relates to applications and methods for plasma treatment of coatings for enhanced biocompatible properties for implanted medical devices, including decreased restenosis and decreased adhesion of cells, such as platelets and leukocytes. The invention further relates to coated medical devices and methods, which include plasma-deposited nitrogen-containing and oxygen-containing coatings, and one or more additional coatings, including siloxane-containing coatings, polyethylene glycol-containing coatings and dextran-containing coatings.
2. Background Art
Note that the following discussion refers to a number of publications by author(s) and year of publication, and that due to recent publication dates certain publications are not to be considered as prior art vis-a-vis the present invention. Discussion of such publications herein is given for more complete background and is not to be construed as an admission that such publications are prior art for patentability determination purposes.
There is a need for coatings and surfaces of medical devices that limit or inhibit restenosis and attachment of cells, particularly attachment of platelets, leukocytes and similar cells. Medical devices, particularly implantable medical devices, frequently result in platelet attachment leading to thrombosis, leukocyte attachment leading to inflammation, and aberrant cellular in-growth leading to fibrosis and related conditions. For example, restenosis is a common problem following stent placement, involving overpopulation by smooth muscle cells with consequent re-narrowing of the lumen of the blood vessel. With stents and other blood-contacting medical devices, including catheters and similar devices, attachment of platelets and leukocytes is a significant problem. Substantial effort has been devoted to finding materials, coatings, surfactants, drugs and other substances that will inhibit either restenosis or attachment of cells.
Implantable medical devices are used for a wide variety of purposes. Thus devices such as stents, shunts, catheters, prosthetic heart valves, pacemakers, pulse generators, cardiac defibrillators, and similar devices and components are used in the treatment of cardiac and other diseases. A variety of screws, anchors, plates, joints and similar devices are used in orthopedic surgery. Catheters, drains, shunts, leads, stimulators, sensors, seeds, inducers and other devices are used in a wide variety of applications. These implantable medical devices are made from a wide variety of materials, including metals, plastics and various polymeric materials.
A large number of coatings have been explored for used with implantable medical devices to improve the biocompatibility or otherwise improve the in vivo behavior of the implant. U.S. Pat. No. 5,338,770 describes methods and materials for coating biomedical devices and implants with poly (ethylene oxide) chains suitable for covalent attachment of bioactive molecules intended to counteract blood-material incompatibility. U.S. Pat. No. 5,463,010 describes membranes, including polymerized aliphatic hydrocyclosiloxane monomers, for use in coating biomedical devices and implants, and suitable for use as a substrate for covalent attachment of other molecules. U.S. Pat. No. 5,824,049 describes multiple-layer coatings, providing for controlled release of a drug or other bioactive materials through a porous layer. U.S. Pat. No. 6,017,577 describes a polyurethane hydrogel coating for use in medical devices. These and a number of other references known in the art provide for some form of coating, and optionally a specific bioactive layer or coating, for use in improving biocompatibility. However, none of these methods or compositions has addressed all of the problems encountered with implantable medical devices, such as restenosis with stents and attachment of platelets and leukocytes, and none have resulted in widespread commercial and industrial acceptance.
There has been interest in use of a variety of substances in medical device coatings to decrease restenosis, cellular attachment or provide other biomedical benefits. For example, U.S. Pat. No. 6,087,479 discloses coatings, such as a nylon or plastic matrix coating, for use with nitric oxide adducts, such as sodium nitroprusside, and U.S. Pat. No. 5,665,077 discloses polymeric coatings with nitroso compounds. A number of articles in the scientific literature disclose related methods, for example, see Mowery K A et al: Preparation and characterization of hydrophobic polymeric films that are thromboresistant via nitric oxide release.
Biomaterials
2000; 21:9-21; and Sly M K et al: Inhibition of surface-induced platelet activation by nitric oxide.
ASAIO J
1995 41:M394-8.
A recognized problem with stents, and particularly coated stents, is that the coating itself induces an inflammatory response or a thrombogenic response, either of which can lead to unwanted biological consequences. Furthermore, both inflammatory responses and thrombogenic responses appear to be implicated in restenosis in that these responses elicit local production or secretion of growth factors, leading to restenosis. A large number of agents have been investigated, used both systemically and locally, to overcome these responses. Tranilast is one such agent, and is a small molecule with a number of biological actions. It is used in Japan as an anti-allergy drug and acts as an anti-inflammatory on mast cells. It also inhibits arterial smooth muscle cell proliferation and migration in vitro and restenosis in vivo. It is currently under evaluation in clinical trials as a systemic agent to limit restenosis following balloon angioplasty. Pactitaxel (taxol) has also been described as having a beneficial effect following local administration, including when used in a stent coating (Herdeg et al.
Semin Interv Cardiol
1999, 3:197-9; Baumbach et al.,
Catheter Cardiovasc Interv
1999, 47:1026). Also, local administration of a glycoprotein IIb/IIIa receptor antagonist or anti-thrombin agent stents reportedly reduced platelet deposition in coronary arteries (Santos et al.
Am J Cardiol
1998, 82:673-5, A8; Kruse
Catheter Cardiovasc Interv
1999, 46:503-7). Intramural delivery of a specific tyrosine kinase inhibitor with a biodegradable stent reportedly suppressed restenotic changes of the coronary artery in pigs in vivo (Yamawaki et al
J Am Coll Cardiol
1998, 32:780-6). Also, dexamethazone has been delivered locally with stents (Lincoff et al.
J Am Coll Cardiol
1997, 29:808-16; Strecker
Cardiovasc Intervent Radiol
1998, 21(6): 487-96).
Plasma processes have been used in manufacture of medical devices, primarily for use in surface cleaning and preparation methods (Aronsson et al.,
J Biomed Mat Res
1997, 35:49-73). However, plasma processes have also been used to introduce groups, such as amine groups, into a surface, as described in U.S. Pat. No. 5,338,770. That patent describes a method of introduction of amine groups using ammonia gas in the plasma chamber at a flow rate of 190 micromoles per second at 170 mTorr absolute pressure, with the target, hollow fibers, exposed to 180 watts at a radio frequency of 13.56 MHz for fifteen minutes. Plasma processes have also been used to introduce various coatings and polymeric groups, as described generally in U.S. Pat. Nos. 5,463,010 (hydrocyclosiloxane membrane), 5,336,518 (heptafluorobutylmethacrylate membrane), 5,962,138 (plasma film layers of various monomers), and other references. However, none of these processes have demonstrated both decreased restenosis and decreased attachment of cells such as platelets and leukocytes when used in vivo.
Thus it would be desirable to provide coatings for surfaces of medical devices which exhibit decreased restenosis and decreased attachment of cells. In particular, it would be desirable to provide methods for preparing and fabricating devices and substrates for treating or preventing hyperplasia, inflammation, thrombosis, and other disease conditions
Chen Meng
Osaki Shigemasa
Zamora Paul O.
BioSurface Engineering Technologies, Inc.
Nakarani D. S.
Peacock Myers & Adams PC
Slusher Stephen A.
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