Coating processes – Medical or dental purpose product; parts; subcombinations;... – Analysis – diagnosis – measuring – or testing product
Reexamination Certificate
2000-03-21
2001-07-24
Cameron, Erma (Department: 1762)
Coating processes
Medical or dental purpose product; parts; subcombinations;...
Analysis, diagnosis, measuring, or testing product
C427S002240, C427S002280, C427S002300
Reexamination Certificate
active
06265016
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to the field of synthetic polymeric coating compositions for polymeric and metal substrates; and, more particularly, to hydrophilic hydrogel coating compositions which are slippery and which exhibit tenacious adherence to the substrate to which they are applied, and to medical devices bearing such hydrogel coatings thereon. Still more particularly, this invention relates to hydrophilic polyurethane hydrogel compositions. The hydrogel coating compositions and coated substrate materials are biocompatible and suitable for use on medical devices which come in contact with various body fluids.
In catheters and many other kinds of medical devices, it is often desirable to coat various plastic, rubber or metal parts thereof with products made from hydrophilic or certain other polymers that are slippery and which produce low coefficients of friction during use. However, one of the problems associated with the utility of such coatings is their inability to remain intact and abrasion-resistant during clinical use in body fluids such as blood. Catheters used in angioplasty, gastroenterology and other medical specialties, are commonly made of polymeric materials which most often are relatively hydrophobic and not inherently slippery or biocompatible. A surface modification is required in order to reduce the friction between the catheter and other devices with which they work, such as vascular sheaths, and also to reduce the friction between the vasculature or other anatomical passageways and the catheter itself. Almost all currently used catheters have some form of surface modification or coating applied to them. The ability of the coating to reduce frictional resistance, its durability, as well as its biocompatibility are the most important functional aspects of an effective surface.
Heretofore, catheters and other medical devices containing synthetic or natural polymers have often been coated with non-permanent compositions such as silicones and other slip agents, fluorocarbons, or hydrogels which, however, were usually not cohesively attached to the substrate surfaces. While such coatings can impart a low coefficient of friction to the surface of a medical device, they typically lack permanence with respect to frictional wear. Fluorocarbons, moreover, may peel or flake from the substrate, or when applied to a soft polymeric substrate material, may cause an increase in the stiffness of the material. In the case of marginally polar substrates used for the fabrication of catheters and other medical devices such as contact lenses, condoms, gastroenteric feed tubes, endotracheal tubes, and the like, a variety of polyurethane based compositions have been suggested as adhesive tie coats. For such uses the coating must exhibit wear permanence, low coefficient of friction in contact with body fluids, as well extremely low toxicity and good biocompatibility. Whereas a number of polyurethane “tie coats” can improve adhesion to plastics and rubbers, they are oftentimes not compatible enough with respect to the polymer surface of the substrates to assure permanence of bonding for the intended medical application. In medical devices this can be a critical requirement for many clinical situations. Particular fields of medical specialties where such factors are important are enumerated below.
In Percutaneous Transluminal Coronary Angioplasty (PTCA) and Percutaneous Transluminal Angioplasty (PTA), the functional characteristics of balloon catheters include trackability through vasculature, crossability and recrossability of stenotic lesions, and retractability through the guiding catheter and the vascular sheath. These are dynamic functions that are fundamental to a successful and efficient interventional angioplasty procedure. They contribute to reduced trauma to the vasculature. In particular, recrossing of stenotic lesions is crucial to a successful outcome. High pressure angioplasty balloons, typically those made of polyethylene terephthalate (PET), can have problems with recrossability. This is because the relatively stiff PET material forms “wings” upon deflation after the first dilation. The winged profile of the deflated balloon can prevent recrossing of the stenotic lesion for a second dilatation. A durable slippery coating can aid in achieving recrossing of the lesion. Guiding catheters are better able to traverse tortuosity in the femoral artery and descending aorta with the help of a good slippery coating.
Stent catheters for use in vascular disease benefit from the characteristics imparted by a good slippery coating. Stent catheter delivery systems used in gastroenterology for opening of biliary passageways also benefit from a slippery coating with regard to traversing passageways leading to the site.
In coronary radiography, diagnostic catheters are used to deliver radiopaque fluid to the coronary arteries for visualization by x-ray fluoroscopy. These catheters benefit in the same way that guide catheters do from a good slippery coating, by aiding in traversing tortuosity in the femoral artery and the descending aorta.
U.S. Pat. No. 4,118,354 discloses the formation of polyurethane hydrogels which are reaction products of a polyisocyanate, having at least two isocyanate groups, and a polyether, produced from a plurality of alkylene oxides, 50 to 90% of which is ethylene oxide, added at random to a polyalcohol having at least two terminal hydroxyl groups, by the dispersal of the prepolymer reaction product into an aqueous liquid phase. Neither the formation of slippery hydrogel barrier coats upon plastic or metal substrates nor the affixation thereof to such substrates by means of covalent chemical bonds to assure durability of said coating upon exertion of dynamic forces thereon are described.
U.S. Pat. No. 4,373,009 describes a method for coating various polymeric substrates with polyurethane prepolymers containing free isocyanate groups and subjecting the thus coated substrates with a second coating of water-soluble copolymers of unsaturated monomers containing at least some isocyanate-reactive monomers as part of their backbone. It is postulated that the isocyanate treatment of the substrate results in firmly anchored tie coats even for polymers containing no isocyanate-reactive groups. No convincing evidence of covalent bonding of the urethane tie coat to the substrate is presented, nor is there any indication that the procedure is suitable for the use in critical medical devices where biocompatibility is a significant issue.
U.S. Pat. Nos. 4,459,317 and 4,487,808 discloses a process for treating a polymer substrate with a first coating of an isocyanate solution containing at least two unreacted isocyanate groups per molecule, and, optionally, a polymer; followed by a second coating of a high molecular weight polyethylene oxide, such that after curing of the isocyanate, the two coatings form a hydrophilic polyethylene oxide-polyurea interpolymer having a low coefficient of friction. Methods for applying a base coat of low molecular weight aromatic or aliphatic polyisocyanates dissolved in suitable organic solvents, followed by evaporating the solvent and then applying a second coat of a high molecular weight polyethyleneoxide polymer dissolved in an organic solvent are also disclosed. The second solution, which may also contain amine catalysts, is then evaporated and the two coatings are heated at elevated temperature in the presence of air which must contain enough moisture to react with the isocyanate of the first coating. The described processes are relatively time-consuming. The isocyanate coating is applied by spraying or dipping the substrate, and no evidence is presented that the isocyanate coating undergoes any reaction with the substrate surface to make it better adhering to the substrate surface. Medical devices made from a polymer substrate to which the coating has been applied, for use in body cavities, including especially the urethra, are also disclosed. Use of the coatings and coated medical devices in a bloo
Ding Ni
Forman Michael R.
Helmus Michael N.
Hostettler Fritz
Rhum David
Cameron Erma
Schneider (USA) Inc.
Vidas Arrett & Steinkraus
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