Coating processes – Medical or dental purpose product; parts; subcombinations;... – Implantable permanent prosthesis
Reexamination Certificate
2001-06-04
2003-09-23
Beck, Shrive P. (Department: 1762)
Coating processes
Medical or dental purpose product; parts; subcombinations;...
Implantable permanent prosthesis
C427S002100, C427S002300, C427S002310, C427S536000, C427S553000, C427S558000, C427S307000, C427S372200
Reexamination Certificate
active
06623786
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates broadly to surface modification of polymeric hydrogels. More particularly, the invention relates to the treatment of ophthalmic lenses, especially siloxane-containing hydrogel contact lenses.
2. Description of the Related Art
Ophthalmic lenses, such as contact lenses, are subject to a myriad of requirements. Among other things, contact lenses must be ocularly-compatible, have a high oxygen permeability, allow sufficient tear exchange, have high visual light transmission, be sufficiently thin to fit between the eye and eye-lid, and be comfortable for the wearer. Although the formation of a contact lens from one core material is desirable from a manufacturing viewpoint, many known contact lens materials have one or more disadvantages. For example, polysiloxanes are known to have high oxygen permeability, which is advantageous for a healthy cornea, but most polysiloxanes have insufficient hydrophilicity to allow adequate lens movement on the eye. In order to combine the advantages of two lens materials, research has been directed to the use of a core material which has been surface-coated to modify the core's surface properties while retaining the bulk material properties of the core.
Generally speaking, methods of treating polymer surfaces include (1) corona discharge, (2) surface degradation or oxidation by oxidizing agents such as chromic acid, (3) plasma treatment and/or plasma polymerization, (4) graft polymerization, and (5) coating. For example, “A Novel Modification of Polymer Surfaces by Photografting” (ACS Synp. Ser. v. 121, pages 217-241) discloses a method of photografting monomers to hydrophobic polymers such as polyethylene and polypropylene in a 0.2 M benzophenone initiator solution.
Another example of photografting of monomers onto polymer surfaces is disclosed in “Photochemical Grafting of Vinyl Monomers onto Starch” (Starch 33 (1981) v. 3, pp. 90-97). This reference discusses the grafting of vinyl monomers onto starch under ultraviolet light excitation in the presence of a wide range of photoinitiators, including benzophenone.
U.S. Pat. No. 4,595,635, issued to Dubrow et al. on Jun. 17, 1986, discloses the surface treating of organopolysiloxane materials to increase the surface tack. One method involves applying a photoinitiator to the organopolysiloxane and irradiating the surface with ultraviolet light. Benzophenone is disclosed as a suitable photoinitiator. The treated materials are useful as tapes, sealants and encapsulants.
U.S. Pat. No. 4,892,402, issued to Sawamoto on Jan. 9, 1990, discloses a method for making hard contact lenses more hydrophilic. The method involves contacting a hard lens with a treatment solution containing a hydrophilic monomer, at least one photosensitizer selected from aromatic ketones or quinones, and a solvent, and then irradiating the lens with ultraviolet light. Thus, the disclosed method is a solvent-based polymerization. Benzophenone is an example of a suitable photosensitizer.
While the exist numerous methods of surface treating polymeric articles, there remain problems with the surface treatment of hydrogel materials, especially those suited as ophthalmic lenses. One problem with many surface grafting techniques is that monomer in the treatment solution may penetrate the hydrogel's polymer matrix, and subsequently bind to the polymer below the article's surface. If substantial monomer penetration occurs, the treated polymeric article may swell and distort from the original shape. Even slight distortion can produce substantial optical distortions in an ophthalmic lens. Thus, there remains a need for a method of surface treating hydrogel materials without substantially modifying the shape of the hydrogel.
SUMMARY OF THE INVENTION
An object of the invention is to modify the surface properties of a polymeric hydrogel, without substantially modifying the shape of the hydrogel.
A further object of the invention is to increase the hydrophilicity of the surface of a polymeric hydrogel, without substantially modifying the shape of the hydrogel.
Another object of the invention is to increase the hydrophilicity of the surface of a hydrophilic ophthalmic lens, without substantially impairing the optical properties of the lens.
One embodiment of the present invention is a method of modifying the surface characteristics of a polymeric article, which includes the following steps:
(a) immersing a polymeric article in a first solution including a benzophenone and at least one solvent for a predetermined time period;
(b) removing said article from said first solution;
(c) evaporating at least a portion of said solvent from said article;
(d) placing said article in a second solution containing at least one macromer; and
(e) applying radiation to said article for a period sufficient to cause at least a portion of said macromers to bond to the surface of said article,
wherein said macromer has a size sufficiently large such that no substantial amount of macromer penetrates said article and causes substantial distortion of said article.
Another embodiment is a polymeric hydrogel article including a core bulk material and a surface coating. The surface coating is formed by graft polymerization with surface photoinitiation in the presence of a benzophenone. The grafted groups are formed from one or more macromers having a size sufficiently large such that no substantial amount of macromer penetrates said lens causing substantial distortion of said lens. The preferred polymeric article is a soft contact lens including a bulk material which is a silicone-containing hydrogel.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following terms are defined at the outset in order to facilitate a clear understanding of the present invention. Certain terms are defined subsequently in the text because of the limited use herein.
The term “copolymer”, as used herein, means polymers formed from two or more monomers or macromers. Thus, copolymer includes terpolymers and the like.
The term “macromer” as used herein refers to a species having at least one unsaturated bond and having at least two repeating monomer units.
The term “hydrogel”, as used herein, refers to a polymeric material which contains at least about 10 weight percent water when fully saturated.
The present invention is a method of modifying the surface characteristics of a polymeric hydrogel. The preferred polymeric articles useful in accordance with the present invention are silicone-containing hydrogel materials. A more preferred subclass of articles which may be treated in accordance with the present invention are ophthalmic lenses, including without limitation thereto, contact lenses, intraocular lenses (i.e., implants), and lenses designed for delivery of pharmaceuticals or other agents to the ocular environment. While contact lenses are the most preferred treatment article, and the invention is discussed primarily with reference to contact lenses, the invention is not so limited.
The advantageous surface treatment method of the present invention generally involves the following steps:
(a) immersing a contact lens in a first solution including a benzophenone and at least one solvent for a predetermined time period;
(b) removing said lens from said first solution;
(c) evaporating at least a portion of said solvent from said lens;
(d) placing said lens in a second solution containing at least one macromer; and
(e) applying radiation to said lens for a period sufficient to cause at least a portion of monomers or macromers to bond to the surface of said lens,
wherein said macromer has a size sufficiently large such that no substantial amount of macromer penetrates said lens causing substantial distortion of said lens.
The term “Photosensitizer”, as used herein include, without limitation thereto, benzophenone, thioxanethen-9-one, 2-acetonaphthone, mixtures thereof and the like.
The term “benzophenone”, as used herein, means benzophenone and derivatives thereof which are suited to initiating surface bonding to a
Baron Richard Carlton
Liu Qin
Gearhart Richard I.
Kolb Michener Jennifer
Meece R. Scott
Novartis AG
Zhou Jian S.
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