Hydrogel with internal wetting agent

Details Hydrogel with internal wetting agent Hydrogel with internal wetting agent

2000-03-22

2002-04-09

Dawson, Robert (Department: 1712)

Optics: eye examining, vision testing and correcting

Spectacles and eyeglasses

Ophthalmic lenses or blanks

C523S106000, C523S107000, C524S858000, C524S865000, C525S165000, C525S279000, C525S431000, C526S279000, C528S025000, C528S032000

Reexamination Certificate

active

06367929

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to hydrophobic polymers. More particularly, it relates to hydrophobic polymers which, when prepared with an internal wetting agent, are suitable for use in biomedical devices such as ophthalmic lenses.
The suitability of a material for use in biomedical devices depends on a number of factors that often include the wettability of the material and its proclivity for adhesion or reaction with biological materials such as proteins and lipids. In ophthalmic applications such as contact lenses and intraocular implants, oxygen permeability is also an important consideration. High oxygen permeability is generally desirable as is good wettability and resistance to adhesion or reaction with biomaterials.
Silicone hydrogels can be a particularly desirable material for making biomedical devices such as contact lenses because of their generally high oxygen permeability. However, their hydrophobic nature make the devices made from them difficult to wet. One approach for dealing with this problem is to coat the hydrogels with a more hydrophilic coating. This adds an additional level of complexity to their manufacture. Additionally, coating material selection can be difficult as can the determination of proper coating thickness, coating uniformity and other factors that can affect physiological performance.
U.S. Pat. No. 5,219,965 and its progeny propose modifying the surface properties of polymeric objects such as contact lenses by the inclusion of macromers having a hydrophobic portion, a hydrophilic portion, a chain transfer agent, and an unsaturated end group in the monomer mix used to make the objects. The macromers can include poly-N-vinylpyrrolidone having molecular weights of 500-10,000 with 1,000-5,000 being most preferred. The macromers are polymerized into the hydrogel and do improve wettability of the polymers. However, the improvement is generally not to such a degree that lenses can be made from the hydrogels without the need for a hydrophilic coating. In any event, enhancing the wettabillty of biomedical devices such as contact lenses without the need for lens coating would be considered a significant advance in the art.
U.S. Pat. Nos. 4,045,547 and 4,042,552 propose the polymerization of large amounts (14.25-35% wt) of polyvinylpyrrolidone (PVP) into a poly(hydroxyethyl methacrylate) (HEMA) based contact lens formulation. The polymerizations are conducted without regard for the presence of water. No mention is made of the molecular weight of the PVP.
U.S. Pat. Nos. 4,833,196; 4,791,175; and 4,678,838 are directed to the incorporation of poly-N-vinyl lactams into polymers used to make contact lenses. Polyvinylpyrrolidone (PVP) is the preferred polylactam Low molecular weight (~40,000 daltons) PVP is covalently bonded with the monomers used to form the lens by first hydroperoxidizing the PVP by reaction with ozone and then polymerizing the PVP with the other monomers.
U.S. Pat. No. 5,198,477 employs low molecular weight (~25,000 daltons) PVP within an interpenetrating polymer network formed principally from macrocycles made from vinyl containing monomers. The PVP appears to be crosslinked into the interpenetrating network.
SUMMARY OF THE INVENTION
The invention is a wettable silicone hydrogel made by including a high molecular weight hydrophilic polymer into the silicone hydrogel monomer mix. The hydrophilic polymer is entrapped in the hydrogel with little or no covalent bonding between it and the hydrogel matrix.
In one aspect of the invention, the high molecular weight hydrophilic polymer is entrapped in the silicone hydrogel matrix.
In another aspect of the invention, the high molecular weight hydrophilic polymer is a polyvinylpyrrolidone.
In yet another aspect of the invention, high molecular weight hydrophilic polymer has a molecular weight (Mw) of 100,000 to 500,000 daltons; preferably, the molecular weight is at least about 300,000 daltons.
In yet a further aspect of the invention, ophthalmic lenses are made from the silicone hydrogels of this invention.
DETAILED DESCRIPTION OF THE INVENTION
The term “monomer” used herein refers to low molecular weight compounds (i.e. typically having number average molecular weights less than 700) that can be polymerized, and to medium to high molecular weight compounds or polymers, sometimes referred to as macromonomers, (i.e. typically having number average molecular weights greater than 700) containing functional groups capable of further polymerization. Thus, it is understood that the terms “silicone-containing monomers” and “hydrophilic monomers” include monomers, macromonomers and prepolymers. Prepolymers are partially polymerized monomers or monomers which are capable of further polymerization.
A “silicone-containing monomer” is one that contains at least two [—Si—O—] repeating units, in a monomer, macromer or prepolymer. Preferably, the total Si and attached O are present in the silicone-containing monomer in an amount greater than 20 weight percent, and more preferably greater than 30 weight percent of the total molecular weight of the silicone-containing monomer. The preferred silicone-containing monomers of this invention have the following structure:
wherein R
51
is H or CH
3
, q is 1 or 2 and for each q, R
52
, R
53
and R
54
are independently ethyl, methyl, benzyl, phenyl or a monovalent siloxane chain comprising from 1 to 100 repeating Si—O units, p is 1 to 10, r=(3−q), X is O or NR
55
, where R
55
is H or a monovalent alkyl group with 1 to 4 carbons, a is 0 or 1, and L is a divalent linking group which preferably comprises from 2 to 5 carbons, which may also optionally comprise ether or hydroxyl groups, for example, a polyethylene glycol chain.
Examples of the silicone-containing monomers of Structure I that can be used to form silicone hydrogels of this invention are methacryloxypropylbis(trimethylsiloxy)methylsilane, methacryloxypropylpentamethyldisiloxane, (3-methacryloxy-2-hydroxypropyloxy) propylbis(trimethylsiloxy)methylsilane. Preferred silicone-containing monomers are monomethacryloxyalkyl terminated polydimethylsiloxanes (“mPDMS”) such as those shown in structure II.
where b=0 to 100, and R
57
is any C
1-10
aliphatic or aromatic group which may include hetero atoms; provided that R
57
is not functionalized at the point at which it is bonded to Si. C
3-8
alkyl groups are preferred with butyl groups, particularly sec-butyl groups, being most preferred. R
56
is an ethylenically unsaturated moiety; prefereably a single polymerizable vinyl group. More preferably it is a methacryl moiety but it can also be an acryl or styrenic moiety or other similar moiety.
It is preferred that additional silicone-containing monomers are combined with the silicone-containing monomers of Stucture I to form the soft contact lenses of the invention. Methacryloxypropyltris(trimethylsiloxy)silane (TRIS), amide analogs of TRIS described in U.S. Pat. No. 4,711,943, and the vinylcarbamate or carbonate analogs described in U.S. Pat. No. 5,070,215 are also suitable for use in this regard Indeed, any known silicone-containing monomer useful for making silicone hydrogels can be used in combination with the silicone-containing monomer of Strucure I to form the soft contact lenses of this invention. Many silicone-containing monomers useful for this purpose are disclosed in U.S. patent application Ser. No. 08/948,128 filed Oct. 9, 1997, incorporated herein by reference. Some examples of other monomers that can be combined with the silicone-containing monomers of Structure I to form the silicone hydrogels of this invention are the hydroxyalkylamine-functional silicone-containing monomers disclosed in U.S. Ser. No. 09/033,348 titled Silicone Hydrogel Polymers by Vanderlaan et al. filed Mar. 2, 1998, and incorporated herein by reference. Linear or branched hydroxyalkylamine-functional monomers comprising a block or random monomer of the following structures can be used:
wherein:
n is 0 to 500 and m is 0 to 500 and (n+m)=10 to 500 and more preferably

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