Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2000-12-01
2002-09-03
Wu, David W. (Department: 1713)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S507000, C604S265000
Reexamination Certificate
active
06444324
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to coating the inner surface of a dilatation balloon so as to reduce friction and thus reduce the required opening pressure upon inflation.
BACKGROUND OF THE INVENTION
Medical balloon catheters having a dilatation balloon located at their distal ends, are used surgically for insertion into blood vessels, urethra, or body conduits for the purpose of reducing stenoses or blockages. Conventionally, such catheters are made of materials such as polyamides, nylon, SELAR®, polyesters such as polyethylene terephthalate (PET), polyethylene (PE), polyester elastomers such as HYTREL®, or similar materials. Also, such balloon catheters can be made of several layers with polyethylene terephthalate blended with polyethylene. Also they can be made with blends of polyethylene terephthalate and HYTREL®. HYTREL® is a randomized block co-polymer of polyethers and polyesters. Such materials are not typically by themselves lubricious in nature, and must be rended lubricious by other means such as coating them with a lubricant.
Balloons are typically tightly folded and wrapped upon themselves for delivery to the targeted lesion, storage and are unwrapped and expanded to a size that is considerably greater than the stored size by the introduction of an expansion fluid into the balloon. It is very difficult, and in fact almost impossible, to do so without having portions stick to each other, and possibly tearing the substrate, particularly in the absence of a lubricious coating. Furthermore, this can greatly increase the amount of opening pressure required to inflate the balloon. Or if using for stent delivery, it will need extra pressure to expand the stent and release it.
One method of overcoming some of these issues has been to coat the outside of the balloon in order to reduce the friction between the folded and wrapped layers. This coating can also provide some protection against pinhole formation in the balloon and/or coating by providing surfaces that do not stick to one another. However, coating the outside surface not only adresses the half of the balloon surface for this, but also may lead to what is referred to in the art as “watermelon seeding.” This refers to slippage of the balloon wherein the balloon which is too lubricious shoots forward on inflation causing accidental slippage from the target or repair site which ultimately may lead to stent slippage from the target site as well.
It is therefore necessary to also find a way in which the balloon can be retained easily at the target site during expansion or contraction without slippage. This is more readily accomplished when the balloon has no lubricity. One method of overcoming this “watermelon seeding” effect is to make the balloons with both a lubricating portion and a non-lubricating portion. U.S. Pat. No. 5,503,631 to Onishi et al. discloses a vasodilating catheter balloon whose body has a lubricating portion and a non-lubricating portion. The lubricious property of the balloon is created by grafting a lubricious coating onto a non-lubricious substrate. Only the tapered portions on opposite ends of the balloon were treated.
Another method of overcoming the “watermelon seeding” is found in U.S. Pat. No. 6,221,467.
Another issue is that if the lubricant utilized on the outside of the balloon is hydrophobic, it may bead or run off when exposed to an aqueous environment, and can consequently reduce lubricity, and lack abrasion resistance. Hydrophilic coatings are an alternative but can also migrate from the balloon surface in an aqueous environment, particularly if they are water soluble, although there are steps that can be taken to prevent migration from occurring through the use of crosslinking or coupling agents, or binders, for instance.
U.S. Pat. No. 5,509,899 describes a medical balloon and catheter in which the balloon is wrapped and folded upon itself tortuously and tightly so that outer surfaces contact each other for insertion into the body and in which the balloon is free of bridging and adhesion between abutting surfaces. The balloon has a base of a continuous polymeric surface expandable from a folded, wrapped configuration with surfaces touching each other into a balloon when inflated, a lubricious, biocompatible, hydrogel coating disposed on the polymeric surface, and a thin, lubricious, blood-compatible coating disposed upon the hydrogel coating which adheres to it to prevent abutting surfaces of the folded polymeric surfaces from adhering to each other during inflation and to prevent delamination of the hydrogel coating and/or rupture of the balloon.
SUMMARY OF THE INVENTION
The present invention relates to a method of coating the inner surface of the dilatation balloon used with a catheter device with a lubricant in order to overcome friction between surfaces in contact with one another and to consequently reduce the opening pressure required to inflate the balloon. This can also avoid the problem of “water melon seeding”.
The dilatation balloon has an inner surface and an outer surface and a lubricious material disposed on the inner surface. The inner surface at least periodically comes into contact with itself. Specifically, dilatation balloons are folded upon themselves for storage. The lubricious material on the inner surface reduces the friction that occurs during inflation of the balloon by reducing or preventing the amount of adhesion occurring between the material of the inner surface as it comes in contact with itself. This lubricious material consequently reduces the opening force required during inflation and thus facilitates an easier inflation. The lubricous material may also reduce pinholeing and ease stent delivery.
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U.S. application No. 09/306,939, Nazarova et al., filed May 7, 1999.
Seppala Jan D.
Sjoquist Scott L.
Yang Dachuan
Lu Caixia
Sci-Med Life Systems, Inc.
Vidas Arrett & Steinkraus P.A.
Wu David W.
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