Coating processes – Direct application of electrical – magnetic – wave – or... – Polymerization of coating utilizing direct application of...
Reexamination Certificate
1999-06-22
2002-08-20
Thibodeau, Paul (Department: 1773)
Coating processes
Direct application of electrical, magnetic, wave, or...
Polymerization of coating utilizing direct application of...
C427S491000, C428S332000, C523S105000, C523S106000, C523S107000, C523S108000
Reexamination Certificate
active
06436481
ABSTRACT:
The present invention relates to coated articles wherein the primary coating comprises a polymer carrying reactive groups. The coating is covalently linked to the surface of the article and exhibits a controlled degree of crosslinking. The invention further relates to the reaction of said primary coatings carrying reactive groups with monomeric, oligomeric or macromolecular compounds of synthetic, semisynthetic or biological origin to provide hybrid-type coated articles and to such articles which exhibit desirable characteristics regarding adherence to the substrate, reactivity, lubricity, durability, biocompatibility, (bio)affinity, (bio)activity, permeability, permselectivity for gases, liquids and solutions, and wettability by aqueous solutions, such as human body fluids. More particularly, the present invention relates to an article, such as a biomedical material or article, especially ophthalmic devices and implants such as artificial corneas, intraocular lenses and contact lenses, including an extended-wear contact lens which is at least partially coated. The articles are obtainable by after-glow plasma-induced polymerization of a polymerizable unsaturated compound having reactive groups, preferably polymerizable vinyl or isopropenyl compounds carrying isocyanato, isothiocyanato, glycidyl, anhydride, azlactone or lactone groups under specific plasma conditions. The invention further relates to such articles carrying a laminate coating obtainable by reacting said reactive groups with a monomeric, oligomeric or macromolecular compound of synthetic, semisynthetic or biological origin.
The provision of a coating on a substrate may generally be desirable for a variety of reasons including protection of the substrate and provision of desirable surface characteristics which the substrate material does not exhibit to the required degree. In the case of biomedical devices, such as ophthalmic devices, e.g. contact lenses it is desirable to have surfaces which are readily wettable by an aqueous liquid such as tear fluid and are capable to retain an aqueous fluid layer which prevents eye irritation and is beneficial for the easy movement of the contact lens on the eye which in turn is important for the comfort of the wearer. The sliding motion of the contact lens is facilitated by the presence of a continuous layer of tear fluid on the contact lens, a layer which lubricates the tissue/lens interface. Additionally, the adhesiveness towards proteins, lipids, minerals, cell debris and other spoilations or micro-organisms and the permeability and stability characteristics of the surface of the contact lens having a coating thereon are of great importance. The permeability of the lens material for gases, water and ions which is required especially in the case of extended wear contact lenses must not be impaired by the coating which is provided in order to impart hydrophilicity to the surface. The coating should exhibit thermal, oxidative and hydrolytic stability as well as resistance to formation of deposits from tear components. Moreover, delamination caused by mechanical stress should not happen. It is of particular advantage the coated article can be sterilized by autoclaving without affecting the uniformity, the thickness and the properties of the coating.
Materials with wettable and biocompatible surfaces are highly desirable for many applications. The wettability of materials is strongly dependent on topography, morphology and on the chemical composition of the material surface. In particular, the ability of the surface to hold a continuous layer of an aqueous solution, such as tear fluid for a prolonged period or time (>10 seconds), is affected by the composition of the material surface. Known attempts to solve the wettability problem in the ophthalmic field include methods for the activation of a device surface. The methods being generic, so that the surface of any material with suitable bulk properties can be converted to be receptive for the covalent immobilization of a coating which is highly retentious for aqueous layers.
A number of surface treatment techniques for polymeric materials are known in the art. Chemical Vapor Depostion (CVD), Corona discharge, ozone treatment, flame treatment, acid etching, and a number of other methods intended to achieve chemical modification of the surface. Among the disadvantages of these techniques are the use of elevated temperatures or the use of hazardous chemicals, the often excessive depth of treatment, non-uniformity of treatment at a microscopic level, and often severe etching and pitting that leads to changes in surface topography. The depth of treatment is important because with clear materials such as those required for lenses the optical clarity and surface smoothness become affected after an excessively harsh treatment. Moreover, surfaces thus treated usually contain complex mixtures of polar groups of sometimes limited stability and are often highly crosslinked which considerably affects the overall permeability characteristics.
Treatment of polymeric surfaces by gas plasmas provides the advantages of very low treatment depth, and high uniformity on a microscopic scale. A gas plasma can for example be generated by glow discharge in a gas atmosphere at reduced pressure (“vacuum”). It creates a stable, partially ionized gas that may be utilized for effecting reactions on the surface of the substrate because the gas plasma environment activates even chemical compounds that are unreactive under normal conditions. The treatment intensity at the surface is generally relatively high, and yet the penetration depth of gas plasma treatment is very low, of the order of 5 to 50 nanometers, at a treatment intensity sufficient for useful surface modification. Surface topography and optical clarity do not change unless exposure to the plasma is performed at high energy levels or for periods of time much exceeding the time required for achieving the desired chemical modification of the surface. Glow discharge plasma reactions therefore result in significantly less alteration of the properties of the bulk material as compared to the alternative treatment technologies described above.
Gas plasma techniques can have two types of outcomes. In the first, commonly called plasma surface treatment, the surface of a polymeric material to be treated (“the substrate”) is subjected to a plasma established in one or more inorganic vapors or some select organic vapors, and the plasma treatment causes the replacement of some of the original chemical groups on a polymer surface by other, novel groups which are contributed from the plasma gas. For instance, the plasma surface treatment of polytetra-fluoroethylene in an ammonia plasma leads to the abstraction of some of the surface fluorine atoms by C—F bond breakage and the incorporation into the modified surface layer of amine groups by C—N bond formation. Plasma surface treatment in an appropriate vapor such as ammonia, oxygen, carbon dioxide, or water vapor, can therefore be used to place on the surface of any polymeric material reactive chemical groups, such as amine, carboxyl, or hydroxyl, suitable for the subsequent covalent immobilization of various molecules. The overall outcome of this technique is a surface functionalization of a substrate material.
The second type of plasma technique is commonly called plasma polymerization and occurs when a discharge is struck in most organic vapors. In contrast to plasma surface treatment, in which less than a monolayer of new material is added, the technique of plasma polymerization leads to the formation of film coatings which can be up to several micrometers thick and can completely mask the substrate.
Plasma polymers are usually covalently bound to the underlying substrate. The covalent attachment of the plasma coating to the bulk material ensures that the plasma polymer does not detach. Furthermore, common plasma polymers are usually highly crosslinked and do not contain leachable low molecular weight fragments which might migrate into body tissue or fluid
Chabrecek Peter
Lohmann Dieter
Gearhart Richard I.
Jackson Monique R.
Meece R. Scott
Novartis AG
Thibodeau Paul
LandOfFree
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