Coating processes – Medical or dental purpose product; parts; subcombinations;... – Implantable permanent prosthesis
Reexamination Certificate
2001-02-09
2003-05-06
Cameron, Erma (Department: 1762)
Coating processes
Medical or dental purpose product; parts; subcombinations;...
Implantable permanent prosthesis
C427S002300, C427S379000, C427S393500, C427S412100
Reexamination Certificate
active
06558734
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods for modifying surfaces of articles.
BACKGROUND
Silicones are widely used in the medical industry. A variety of products are made from silicones including implantable leads, catheters, sensors, and shunts. The wide usage of silicones is due to the variable mechanical properties, the ease of manufacture, the low rate of degradation, and high oxygen transfer. However, silicones lack a number of surface related properties that are desirable in the medical device industry, such as lubricity, hydrophilicity, and blood compatibility.
A variety of approaches have been undertaken in attempts to modify the surface properties of silicones to make them more attractive substrates for the medical device industry. However, the success of the various approaches has been limited by the inherent hydrophobicity and inertness of the silicone surface. Approaches that have been used in attempts to activate the surface include flame treatment, acid treatment, and corona discharge treatment. The utility of these approaches has been limited by a variety of problems including, for example, the use of corrosive chemicals and/or the necessity of oxygen exclusion. In addition, some of the approaches require that the low molecular weight silicones that are present in commercial silicones be extracted before the surface treatment is carried out.
A need exists in the medical device industry for a simple and effective method of modifying the surface of silicones to provide desirable surface properties.
A few reports of surface modification have appeared in the art, some examples of which may be found in the patents and publications listed in Table 1 below.
TABLE 1
Patents and Publications
U.S. Pat./Publication No.
Inventor(s)
Issue/Publication Date
U.S. Pat. No. 5,607,475
Cahalan et al.
4 March 1997
U.S. Pat. No. 4,822,741
Banes
18 April 1989
Technical Publications
Iwata et al.,
J. Applied Polymer Science,
49:1041-46 (1993). Rubber Fabrication: Silastic Silicone Rubber, Dow Corning (Midland, Mich.), Copyright 2000.
All patents and publications listed in Table 1 above are hereby incorporated by reference herein in their respective entireties. As those of ordinary skill in the art will appreciate readily upon reading the Summary of the Invention, Detailed Description of the Preferred Embodiments, and claims set forth below, many of the devices and methods disclosed in the patents and publications of Table 1 may be modified advantageously by using the teachings of the present invention.
SUMMARY OF THE INVENTION
The present invention has certain objects. That is, various embodiments of the present invention provide solutions to one or more problems existing in the prior art with respect to methods for preparing articles having modified silicone surfaces. Those problems include methods that require the use of corrosive chemicals, methods that require oxygen exclusion, methods that require the extraction of low molecular weight silicones, and methods that lead to poor surface properties (e.g., adhesion and uniformity) due to factors including, for example, the presence of unextracted low molecular weight silicones in the article and the inert chemical nature of the silicone itself. Various embodiments of the present invention have the object of solving at least one of the foregoing problems. While some methods were capable of solving at least some of the foregoing problems, they were generally not employed because of their prohibitively high cost or difficult manufacturing processes. It is therefore another object of the present invention to provide an improved method that may allow the surface-modified articles to be economically manufactured and sold at low cost, yet still fulfill at least one of the foregoing objects.
In comparison to known methods for preparing articles having silicone surfaces, various embodiments of the present invention may provide one or more of the following advantages. The present invention may provide articles having modified silicone surfaces with improved properties over articles with silicone surfaces known in the art. For example, surface-modified articles of the present invention are preferably biocompatible. Biocompatibility may be important in preventing complications such as adverse reactions by the body when the article is inserted in human or animal tissue.
The present invention also provides advantageous methods for preparing articles having modified silicone surfaces. Methods of the present invention allow for surface modification of such articles without the need for extracting low molecular weight silicones. Such methods may provide economic advantages as well as product quality improvements. For example, methods of the present invention preferably may be carried out by simple, rapid procedures without the need for expensive equipment.
Definitions
As used herein, “silicone” refers to a polysiloxane. Preferably silicones are poly(diorganosiloxanes). Preferably silicones are elastomeric.
As used herein, “elastomeric” refers to substances having the properties of natural, reclaimed, vulcanized, or synthetic rubber, in that they stretch under tension, have a high tensile strength, retract rapidly, and recover to about their original dimensions. Preferably elastomers have a tensile strength of at least about 2 megapascals (MPa) (290 pounds per square inch, psi) and more preferably at least about 4 MPa (580 psi). Preferably elastomers have an elongation at break of at least about 50% and more preferably at least about 100%.
As used herein, “surface-modified” refers to material that is chemically or physically altered in a surface layer compared to the material in the layer below the surface layer. Preferably the surface-modified layer is at least about 1 micrometer thick and at most about 100 micrometers thick.
An “amide-functional surface” refers to a material having at least amide-functional groups on the surface. An “amine-functional surface” refers to a material having at least amine-functional groups on the surface. The surface can also include other functional groups. Surfaces having such functional groups (amide groups, amine groups, etc.) are referred to herein as “functionalized” surfaces. Preferably the functionalized surface includes a polymer and more preferably a hydrogel polymer. Generally, a hydrogel polymer is distinct from a solid polymeric material in the amount of water contained therein. Typically, a solid polymeric material includes less than about 10% by weight water.
As used herein, the term “curing” includes hardening, crosslinking, polymerizing, chain extending, and other related chemical reactions. Preferably a cured material has undergone sufficient hardening, crosslinking, polymerizing, or chain extending to provide a material in the solid state.
As used herein, “partially-cured” means that peroxide remains that has not decomposed during the curing reaction.
A “medical device” may be defined as a device that has surfaces that contact tissue, blood, or other bodily fluids in the course of their operation, which fluids are subsequently used in patients. This can include, for example, extracorporeal devices for use in surgery such as blood oxygenators, blood pumps, blood sensors, tubing used to carry blood or other devices that contact blood which is then returned to the patient. This can also include endoprostheses implanted in blood contact in a human or animal body such as vascular grafts, stents, pacemaker leads, heart valves, and the like that are implanted in blood vessels or in the heart. This can also include devices for temporary intravascular use such as catheters, guide wires, and the like, which are placed into the blood vessels or the heart for purposes of monitoring or repair.
As used herein, “biologically active agent” means a substance that has an effect on living tissue. Biologically active agents include, for example, therapeutic agents, which are substances that tend to prevent and/or overcome disease and/or promote recovery. As such, biologically active agents also incl
Iwata Hiroo
Koulik Edouard
Patrick Cahalan T.
Berry Tom G.
Cameron Erma
Medtronic Inc.
Waldkoetter Eric R.
Woods Thomas F.
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