Coated articles

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2001-05-30

2003-07-08

Nakarani, D. S. (Department: 1773)

Stock material or miscellaneous articles

Composite

Of addition polymer from unsaturated monomers

C427S002240, C427S508000, C428S500000, C428S515000, C428S522000

Reexamination Certificate

active

06589665

ABSTRACT:

The present invention relates to coated articles such as biomedical articles, especially contact lenses, which are at least partly coated with a hydrophilic polymer, and to a process for the manufacture of said coated articles.
A variety of different types of processes for preparing hydrophilic polymeric coatings on an “inert” hydrophobic substrate have been disclosed in the prior art. For example, WO 99/57581 discloses to first of all provide the article surface with covalently bound photoinitiator molecules, coating the modified surface with a layer of a polymerizable macromonomer and then subjecting it to a heat or radiation treatment whereby the macromonomer is graft polymerized thus forming the novel article surface. The covalent binding of the photoinitiator molecules to the article surface is created by first subjecting the article surface to a plasma treatment thereby providing the surface with functional groups, and then reacting said functional groups with coreactive groups of a functional photoinitiator.
A plasma treatment requires a considerable investment in equipment and is furthermore difficult to be integrated in an automated production process. For example, a plasma treatment requires that the article to be treated is dry before exposure to the plasma. Thus, a polymeric article such as a contact lens that is wet from prior hydration or extraction must be dried previously, thereby adding time in the overall lens production process as well as imposing added costs of obtaining a drying equipment.
Therefore, it would be highly desirable to modify the surface functionalization step of the process disclosed in WO 99/57581 such that the plasma treatment is avoided and replaced by a technique which is easy to perform with standard equipment and which is thus more feasible for an automated production process.
Surprisingly, it has now been found, that hydrophobic articles may be readily functionalized by adding at least one polyelectrolyte or preferably a bilayer of functional polyelectrolytes to the article surface. The functional groups of the polyelectrolytes that are adsorbed and/or heteropolarly bound on the surface then may be used for the covalent attachment of polymerization initiators which in turn may initiate the graft polymerization of suitable hydrophilic monomers or macromonomers onto the article surface.
The present invention therefore in one aspect relates to a composite material comprising
(a) an inorganic or organic bulk material having attached to its surface a polyionic material that comprises covalently bound initiator moieties for radical polymerization; and
(b) a hydrophilic surface coating obtainable by applying one or more different ethylenically unsaturated hydrophilic monomers or macromonomers to the bulk material surface provided with the initiator radicals and polymerizing said monomers or macromonomers.
The bulk material underlying the composite materials of the invention is preferably a material that is devoid of ionic groups such as cationic or anionic groups. Accordingly, the surface of the preferred bulk materials is also devoid of ionic groups such as carboxy, sulfo, amino and the like groups and is thus substantially free from ionic charges.
Examples of suitable bulk materials 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 or modified biopolymers 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, polyacrylamides, polymethacrylamides, polystyrene, polyethylene and halogenated derivatives thereof, polyvinyl acetate and polyacrylonitrile); or elastomers (silicones, polybutadiene and polyisoprene).
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, perfluoroalkyl polyethers, 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 or propylene, for example 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 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.
A particular preferred group of bulk materials comprises organic polymers selected from polyacrylates, polymethacrylates, polyacrylamides, poly(N,N-dimethylacrylamides), polymethacrylamides, polyvinyl acetates, polysiloxanes, perfluoroalkyl polyethers, fluorinated polyacrylates or -methacrylates and amphiphilic segmented copolymers comprising at least one hydrophobic segment, for example a polysiloxane or perfluoroalkyl polyether segment or a mixed polysiloxane/perfluoroalkyl polyether segment, and at least one hydrophilic segment, for example a polyoxazoline, poly(2-hydroxyethylmethacrylate), polyacrylamide, poly(N,N-dimethylacrylamide), polyvinylpyrrolidone polyacrylic or polymethacrylic acid segment or a copolymeric mixture of two or more of the underlying monomers.
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 Silastic™ type polymer, or a composite made therefrom.
Moreover, the material to be coated may also be an inorganic or metallic base material 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 are very useful. In addition, e.g. for biosensor purposes, hydrophilically coated base materials are expected to reduce nonspecific binding effects if the structure of the coating is well controlled. Biosensors may require a specific carbohydrate coating 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, for example intraocular lenses, artificial cornea or in particular contact lenses.
The polyionic material being attached to the bulk material surface may consist of one single ionic polymer, for example of a polyanionic or polycationic material as described below.
Preferably, the polyionic material includes at least one bilayer, the bilayer comprising a first ionic polymer and a second ionic polymer having charges opposite of the charges of the first ionic polymer.
A suitable bilayer on the b

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