Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Reexamination Certificate
1998-07-15
2002-11-19
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
C428S936000, C523S106000, C525S937000, C427S446000, C427S447000, C427S450000
Reexamination Certificate
active
06482531
ABSTRACT:
TECHNICAL FIELD
This invention relates to devices having gas-phase deposited coatings and their methods of production. More specifically, this invention relates to devices, and their method of production, having gas-phase deposited coatings which are non-fouling and wettable.
BACKGROUND
The chemical composition of surfaces plays a pivotal role in dictating the overall efficacy of many devices. Some devices require non-fouling, and wettable surfaces in order for the devices to be useful for their intended purposes. For example, many biomedical devices such as catheters, stents, implants, interocular lenses and contact lenses require surfaces which are biologically non-fouling, which means that proteins, lipids, and cells will not adhere to the surfaces of the devices. In some cases materials for devices are developed which have all the necessary attributes for their intended purposes, such as, strength, optimal transmission, flexibility, stability, and gas transport except that the surfaces of the materials will foul when in use. In these cases either new materials for the devices are developed or an attempt to change the surface characteristics of the materials is made.
In the specific case of contact or interocular lenses, particularly contact lenses, although many polymeric materials possess the necessary mechanical, oxygen permeation and optical properties required for lens manufacture, many potential contact lens materials are subject to rapid biological fouling due to the adhesion of proteins, lipids, and other molecules present in the tear fluid surrounding the lens, and/or the surface energies of the materials are too low making the contact lenses too hydrophobic, and therefore not wettable by the tear fluid.
In light of the above considerations, a common approach utilized by various researchers is to attempt to improve the biocompatibility of the potential contact lens materials by application of a thin coating to these substrates. In theory such a coating would take advantage of the inherent favorable bulk mechanical, gas transport and optical properties of the polymer with the applied coating providing the required hydrophilicity and non-fouling properties. However, despite the plethora of such studies, it is significant to note that, at present, not a single contact lens manufacturer offers commercial products having coatings applied for this express purpose. Obviously, although the concept of simply applying a surface coating to remedy physical property deficiencies of a given polymer substrate has theoretical appeal, this has proven to be a totally illusive goal in actual practice. The previous failures reflect the fact that, to be commercially viable, a successful contact lens coating procedure must satisfy a myriad of rather stringent requirements. These requirements, as a minimum, include the following criteria: the coatings must be uniform and, ideally, pin-hole free; the coatings must be both wettable and non-biologically fouling; the coatings should be essentially devoid of extractables and they must exhibit long-term chemical stability in aqueous saline solution; the coatings must exhibit excellent optical transparency in the visible region of the electromagnetic spectrum; the coatings must not compromise the oxygen permeability (i.e., the so-called DK value) of the polymer substrate; and, in the case of reusable lenses, the coatings must exhibit sufficient abrasion resistance and chemical stability to withstand repeated cleanings. In the latter case, cleaning procedures would include both exposure to harsh chemical cleansing agents and to mechanical rubbing actions.
European Patent Application 93810399.1, filed Jun. 2, 1993, describes a complicated multi-step process to alter the surface of a contact lens material. The process requires a plasma treatment of the surface to generate surface free radicals, which are reacted with oxygen to form hydroperoxy groups, to which are graft polymerized an ethylenically unsaturated monomer plus cross-linking agent, followed by a solution extraction period to remove unreacted monomers. This complex process requires the presence of inhibition agents during the monomer coupling reactions to prevent the homopolymerization of the ethylene monomers by free radicals generated during the thermal decomposition of the hydroperoxy groups.
The plasma deposition of triethylene glycol monoallyl ether is reported in the German patent application DE19548152.6. Although it did not deal with contact lenses, it centered on surface modifications to reduce the adsorption of biological compounds. Coatings of such type would be useful in reducing non-specific protein adsorption on certain biosensor surfaces. In this work, substrates for coating were located outside the plasma discharge zone and exceptionally low RF power densities were employed in an attempt to minimize fragmentation of the polyethylene oxide units present in this monomer. Not unexpectedly, coatings deposited in the relatively non-energetic region upstream of the plasma discharge and outside the luminous discharge zone were only weakly attached to the underlying substrates. Another problem encountered in this work was the low volatility of the monomer. This resulted in a requirement for monomer heating to provide sufficient vapor for the plasma deposition process. However, even with heating, the vapor pressures obtainable without initiating thermal decomposition of the monomer were too low to provide any sort of flow rate and/or reactor pressure controllability. Additionally, the unusually low vapor pressure resulted in exceptionally low film deposition rates with accompanying film non-uniformity. The coatings obtained were not tested for adhesion under flow conditions, nor were they subjected to any abrasive cleaning or rubbing actions. Simple soaking of the coating substrates in distilled water for relatively short periods (e.g., less than 48 hours) resulted in measurable changes in the chemical compositions of the coatings as revealed by XPS surface analysis of these coatings before and after the simple water immersion test.
U.S. Pat. Nos. 3,008,920 and 3,070,573 reveal the use of plasma surface treatments to generate free radicals for subsequent peroxy group formation followed by the grafting of vinylic monomers to the polymer substrate. The control of the depth uniformity and density of the grafted coatings is a difficult problem encountered in these grafting experiments.
PCT/US90/05032 (Int. Publication #W091/04283) discloses increasing the wettability of polymeric contact lens materials synthesized from specific hydroxy acrylic units and vinylic siloxane monomers by grafting other molecules to the surface. The only examples of the proposed grafting procedure described in this patent involve attachment of specific polyols by wet chemical procedures, but this patent does suggest that hydroxy acrylic units may be grafted to the specific hydroxy acrylic/siloxane polymeric materials by radiation methods. Additionally, radiation induced attachment by gaseous hydroxyl acrylic units was described in U.S. Pat. No. 4,143,949 as a means of improving surface hydrophilic character.
U.S. Pat. No. 4,143,949 discloses a process for putting a hydrophilic coating on a hydrophoic contact lens. The polymerization is achieved by subjecting a monomer, in gaseous state, to the influence of electromagnetic energy, of a frequency and power sufficient to cause an electrodeless glow discharge of the monomer vapor.
U.S. Pat. No. 4,693,799 describes a process for producing a plasma polymerized film by pulse discharging. The process comprises forming a plasma polymerized film on the surface of a substrate placed in a reaction zone by subjecting an organic compound containing gas to plasma polymerization utilizing low temperature plasma formed by pulse discharging, in which the time of non-discharging condition is at least 1 msec, and the voltage rise time for gas breakdown is not longer than 100 msec. Specifically, the patent disclosed a process employing an alternating current (“AC”) electri
Savage Charles R.
Timmons Richard B.
Wang Jenn-Hann
Wu Yuliang
Board of Regents , The University of Texas System
Jackson Walker L.L.P.
Thibodeau Paul
Zacharia Ramsey
LandOfFree
Non-fouling, wettable coated devices does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Non-fouling, wettable coated devices, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Non-fouling, wettable coated devices will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2987466