Coating process

Details Coating process Coating process

2000-10-27

2003-06-24

Beck, Shrive P. (Department: 1762)

Coating processes

Medical or dental purpose product; parts; subcombinations;...

Implantable permanent prosthesis

C427S002100, C427S002310, C427S487000, C427S491000, C427S301000, C427S322000, C427S333000, C427S407100

Reexamination Certificate

active

06582754

ABSTRACT:

The present invention is directed to a process for the manufacture of branched and optionally crosslinked coatings on bulk polymeric materials with high wettability by aqueous biological media and minimal irreversible adsorption of proteins, and their use for biomedical applications, especially contact lenses including extended-wear contact lenses. The need for highly wettable, minimally protein-fouling coatings is well recognized particularly in the contact lens field. Bulk polymeric materials that possess high oxygen permeability are of great interest for application as extended wear contact lenses. Unfortunately polymers that provide high oxygen transmission possess a relatively hydrophobic surface even if their water content is in the range of 20 to 30%. This leads to excessive discomfort and unacceptably rapid dewetting of the lens by the tear film when such lenses are worn by humans. Hence such contact lens bulk materials must be equipped with a coating that allows good wetting by the human tear fluid. Application of thin polymeric coatings, for instance from gas plasmas (glow discharges) struck in methane/air mixtures ameliorates this problem and enables comfortable wear of such composite lenses. However, the irreversible deposition of biological molecules (biofouling), particularly proteins, onto such coated lenses can lead to the onset of symptoms of discomfort in some wearers and therefore still presents a drawback that needs to be overcome to obtain an ultimately comfortable lens for even the most sensitive wearers.
It is the object of the present invention to provide hydrophilic polymer coatings that have the desirable property of providing superior resistance to fouling of contact lenses by tear film proteins while also allowing high wettability by the tear film. Surprisingly, this can be achieved by the use of branched and optionally crosslinked hydrophilic polymer-containing chains. The coatings of the present invention have been found to result in no observable protein adsorption even when complex multi-protein solutions were used, such as human tear fluid. Exposure to multicomponent protein media presents a far more demanding challenge for coatings intended to be protein-resistant than exposure to single protein solutions, and hence the protein-resisting abilities of the coatings of the present invention are clearly demonstrated.
The present invention therefore in one aspect relates to a process for coating a material surface, comprising the steps of: Coating Process
(a) covalently binding a compound comprising an ethylenically unsaturated double bond to the material surface;
(b) polymerizing a monomer comprising a reactive or crosslinkable group on the surface and thereby providing a primary polymer coating comprising reactive or crosslinkable groups,
(c) in case of a monomer comprising a reactive group in step (b) reacting the reactive groups of the primary coating with a further compound comprising an ethylenically unsaturated double bond and graft-polymerizing a hydrophilic monomer and optionally a co-monomer having a crosslinkable group onto the primary coating obtained according to step (b) and
(d) in case of crosslinkable groups being present in step (b) or (c) initiating crosslinking of said groups.
Examples of materials that may be coated according to the process of the invention are quartz, ceramics, glasses, silicate minerals, silica gels, metals, metal oxides, carbon materials such as graphite or glassy carbon, natural or synthetic organic polymers, or laminates, composites or blends of said materials, in particular natural or synthetic organic polymers which are known in large number. Some examples of polymers are polyaddition and polycondensation polymers (polyurethanes, epoxy resins, polyethers, polyesters, polyamides and polyimides); vinyl polymers (polyacrylates, polymethacrylates, polystyrene, polyethylene and halogenated derivatives thereof, polyvinyl acetate and polyacrylonitrile); elastomers (silicones, polybutadiene and polyisoprene); or modified or unmodified biopolymers (collagen, cellulose, chitosan and the like).
A preferred group of materials to be coated are those being conventionally used for the manufacture of biomedical devices, e.g. contact lenses, in particular contact lenses for extended wear, which are not hydrophilic per se. Such materials are known to the skilled artisan and may comprise for example polysiloxanes, perfluoropolyethers, fluorinated poly(meth)acrylates or equivalent fluorinated polymers derived e.g. from other polymerizable carboxylic acids, polyalkyl (meth)acrylates or equivalent alkylester polymers derived from other polymerizable carboxylic acids, or fluorinated polyolefines, such as fluorinated ethylene propylene, or tetrafluoroethylene, preferably in combination with specific dioxols, such as perfluoro-2,2-dimethyl-1,3-dioxol. Examples of suitable bulk materials are e.g. Lotrafilcon A, Neofocon, Pasifocon, Telefocon, Silafocon, Fluorsilfocon, Paflufocon, Silafocon, Elastofilcon, Fluorofocon or Teflon AF materials, such as Teflon AF 1600 or Teflon AF 2400 which are copolymers of about 63 to 73 mol % of perfluoro-2,2-dimethyl-1,3-dioxol and about 37 to 27 mol % of tetrafluoroethylene, or of about 80 to 90 mol % of perfluoro-2,2-dimethyl-1,3-dioxol and about 20 to 10 mol % of tetrafluoroethylene.
Another preferred group of materials to be coated are those being conventionally used for the manufacture of biomedical devices, e.g. contact lenses, which are hydrophilic per se, since reactive groups, e.g. carboxy, carbamoyl, sulfate, sulfonate, phosphate, amine, ammonium or hydroxy groups, are inherently present in the material and therefore also at the surface of a biomedical device manufactured therefrom. Such materials are known to the skilled artisan and comprise for example polyhydroxyethyl acrylate, polyhydroxyethyl methacrylate (HEMA), polyvinyl pyrrolidone (PVP), polyacrylic acid, polymethacrylic acid, polyacrylamide, polydimethylacrylamide (DMA), polyvinyl alcohol or copolymers for example from two or more monomers from the group hydroxyethyl acrylate, hydroxyethyl methacrylate, N-vinyl pyrrolidone, acrylic acid, methacrylic acid, acrylamide, dimethyl acrylamide, vinyl alcohol and the like. Typical examples are e.g. Polymacon, Tefilcon, Methafilcon, Deltafilcon, Bufilcon, Phemfilcon, Ocufilcon, Focofilcon, Etafilcon, Hefilcon, Vifilcon, Tetrafilcon, Perfilcon, Droxifilcon, Dimefilcon, Isofilcon, Mafilcon, Nelfilcon or Atlafilcon.
Still another group of preferred materials to be coated are amphiphilic segmented copolymers comprising at least one hydrophobic segment and at least one hydrophilic segment which are linked through a bond or a bridge member. Examples are silicone hydrogels, for example those disclosed in PCT applications WO 96/31792 and WO 97/49740 which are herewith incorporated by reference.
The material to be coated may also be any blood-contacting material conventionally used for the manufacture of renal dialysis membranes, blood storage bags, pacemaker leads or vascular grafts. For example, the material to be modified on its surface may be a polyurethane, polydimethylsiloxane, polytetrafluoroethylene, polyvinylchloride, Dacron™ or a composite made therefrom.
Moreover, the material to be coated may also be an inorganic or metallic base material with or without suitable reactive groups, e.g. ceramic, quartz, or metals, such as silicon or gold, or other polymeric or non-polymeric substrates. E.g. for implantable biomedical applications, ceramics or carbohydrate containing materials such as polysaccharides are very useful. In addition, e.g. for biosensor purposes, dextran coated base materials are expected to reduce nonspecific binding effects if the structure of the coating is well controlled. Biosensors may require polysaccharides on gold, quartz, or other non-polymeric substrates. The form of the material to be coated may vary within wide limits. Examples are particles, granules, capsules, fibres, tubes, films or membranes, preferably moldings of all kinds such as ophthalmic moldings, in p

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