Coating processes – Medical or dental purpose product; parts; subcombinations;... – Implantable permanent prosthesis
Reexamination Certificate
1998-01-30
2001-04-24
Beck, Shrive (Department: 1762)
Coating processes
Medical or dental purpose product; parts; subcombinations;...
Implantable permanent prosthesis
C427S002280, C427S002300, C427S409000, C604S019000, C604S317000
Reexamination Certificate
active
06221425
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the field of lubricious hydrophilic coatings for intracorporeal medical devices, and more particularly to a lubricious hydrophilic coating grafted onto a catheter or onto a guidewire.
The use of a medical devices within a patient may be facilitated by the presence of a lubricious surface on the device. For example, intravascular devices, such as catheters and guidewires, are more easily maneuvered within a patient's vasculature when the friction between the walls of the vessel and the intravascular device is reduced. The friction may be reduced by coating the device with a hydrophilic compound which becomes slippery after adsorbing an appreciable amount of water. Consequently, the hydrophilic coating provides lubricity when the coated device is exposed to aqueous solution, as when the coated device is exposed to water prior to insertion in the patient or to the patient's blood during use. Alternatively, coatings, such as fluoropolymers, and silicone, provide lubricity to the surface of an intracorporeal device without the need for exposure to aqueous solution. However, the degree of lubricity may vary greatly depending on the nature of the lubricious coating. Hydrophilic coatings provide superior lubricity compared to hydrophobic coatings, such as silicone, when tested against a biological tissue countersurface.
In addition to lowering the coefficient of friction of the coated device, an effective lubricious coating must strongly adhere to the device surface. The lubricious coating should remain adhered to the device surface during potentially extended periods of storage, as well as in response to abrasive forces encountered during use. Poor adhesive strength is undesirable because the lost coating may be left behind inside the patient during use, with a corresponding decrease in the lubricity of the device. Typically, a trade off exists between a coating's lubricity and the coating's adhesive and cohesive strength, so that attempts to increase the adhesive strength of lubricious coatings may inadvertently decrease the lubricity of the coating. Consequently, one difficulty has been providing a highly lubricious coating that strongly adheres to a device surface.
It would be a significant advance to provide a hydrophilic coating which strongly adheres to a surface of a medical device to render the device highly lubricious. The present invention satisfies these and other needs.
SUMMARY OF THE INVENTION
The invention is directed to a method of providing a lubricious hydrophilic coating on an intracorporeal medical device, and the coated medical device produced thereby. A durable hydrophilic coating is provided on the medical device, which is highly lubricious when in contact with body fluids.
In one embodiment, the hydrophilic coating on the intracorporeal medical device generally includes a base coat and a lubricious hydrophilic top coat. The base coat has a binding component and a grafting component, and is used to strongly bind the hydrophilic top coat to the medical device. Specifically, the binding component binds to both the hydrophilic polymer and to the grafting component, and the grafting component grafts to the device surface. In the method of providing a lubricious hydrophilic coating on a device, the device is first coated with a solution which contains both the grafting component and the binding component. The coated device is then exposed to polymerizing radiation to polymerize the grafting component and form a base coat on the device. The device is then coated with a solution of the hydrophilic top coat, and the coated device allowed to dry, to form a hydrophilic coating on the device. Because the top coat bonds to the base coat during drying, the hydrophilic coating produced will not readily wear off, even after repeated hydration and abrasion.
In another embodiment, a base coat is not used, and the hydrophilic coating on the intracorporeal medical device generally includes a hydrophilic polymer, an ionic compound with at least one inorganic ion, and a grafting component. The grafting component is polymerized as outlined above, so that the grafting component grafts to the device and crosslinks to the hydrophilic polymer, to form a hydrophilic coating on the device. When the coated device is hydrated, the coating absorbs water and is highly lubricious, but does not dissolve in the aqueous or blood medium because the hydrophilic polymer is immobilized by the grafted network. Moreover, the ionic compound, or salt, increases the lubricity of the hydrophilic coating by providing uncrosslinked domains in the crosslinked matrix. Because the ability of a hydrophilic polymer to absorb water is decreased when the polymer is crosslinked, the salt enhances the polymer lubricity by disrupting the crosslinking of the hydrophilic polymer into the grafting component crosslinked network. Therefore, when the hydrophilic coating is hydrated by exposure to a solvent and the salt dissolves, these uncrosslinked domains provide additional lubricity by increasing the contact between the hydrophilic polymer and the countersurface, e.g. the patient's vessel wall, and hence additional lubricity.
To hydrate the hydrophilic coating on the device and render the coating highly lubricious, the coated device may be exposed to aqueous fluid either before insertion into a patient or by contact with body fluid while inside the patient.
The hydrophilic coating of the invention can be applied to any device having a polymeric surface, as for example, a catheter formed of conventional materials. For example, the catheter components may be formed of high density polyethylene, polyethylene terephthalate, and polyolephinic ionomers such as Surlyn®), nylon and the like which are frequently used to form dilatation balloons or catheter shafts. Additionally, the device may be a metal device, such as a metal guidewire, that has been coated with a polymeric primer coating to produce a polymeric surface.
The coated device of the invention has a superior hydrophilic coating which is highly lubricious against biological tissue and is strongly bound to the device surface due to the grafting component used alone or in combination with the binding component. In the case of a PTCA catheter or guidewire, the coating serves to enhance device access to distal lesions and the ease with which a device crosses small diameter athlerosclerotic lesions. These and other advantages of the invention will become more apparent from the following detailed description of the invention and the accompanying exemplary drawings.
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Bigus Stephen James
Michal Eugene T.
Advanced Cardiovascular Systems Inc.
Beck Shrive
Chen Bret
Heller,. Ehrman White & McAuliffe LLP
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