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Drug delivery endovascular stent and method of use

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Title: Drug delivery endovascular stent and method of use.
Abstract: A radially expandable, endovascular stent designed for placement at a site of vascular injury, for inhibiting restenosis at the site, a method of using, and a method of making the stent. The stent includes a radially expandable body formed of one or more metallic filaments where at least one surface of the filaments has a roughened or abraded surface. The stent may include a therapeutic agent on the abraded surface. ...


Browse recent Biosensors International Group patents - Hamilton, BM
Inventors: Douglas R. Savage, John E. Schulze, Ronald E. Betts, Sepehr Fariabi, Shih-Horng Su
USPTO Applicaton #: #20120029626 - Class: 623 142 (USPTO) - 02/02/12 - Class 623 
Prosthesis (i.e., Artificial Body Members), Parts Thereof, Or Aids And Accessories Therefor > Arterial Prosthesis (i.e., Blood Vessel) >Drug Delivery

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The Patent Description & Claims data below is from USPTO Patent Application 20120029626, Drug delivery endovascular stent and method of use.

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This application claims the benefit of priority to U.S. Provisional Application No. 60/853,077, filed Oct. 20, 2006.

BACKGROUND

Complications such as restenosis are a recurring problem in patients who have received artherosclerosis therapy in the form of medical procedures such as percutaneous transluminal coronary angioplasty (PTCA). Restenosis is commonly treated by a procedure known as stenting, where a medical device is surgically implanted in the affected artery to prevent it from occluding post procedure.

A stent is typically cylindrical in shape and is usually made from a biocompatible metal, such as titanium or surgical steel. Most stents are collapsible and are delivered to the occluded artery via transluminal catheter. The stent is affixed to the catheter and can be either self expanding or expanded by inflation of a balloon inside the stent that is then removed with the catheter once the device is in place. Examples of common types of stents are disclosed in U.S. Pat. No. 6,936,066 to Palmaz entitled “Complaint Implantable Medical Devices and Methods of Making Same.”

Complications that arise from stent therapy are restenosis and thrombosis. In an effort to overcome these complications, stents are routinely developed to have the additional feature of controlled drug elution. To accomplish this, a metal stent is coated with an API mixed with polymer, as disclosed in U.S. Pat. No. 5,716,981 issued to Hunter entitled anti-angiogenic Compositions and Methods of Use. Examples of typical therapies that are delivered in this manner are antiproliferatives, anticoagulants, anti-inflammatory agents and immunosuppressive agents, though there are many other chemical and biological agents that can be used. A porous layer of biodegradable material is often applied over the coating layer to regulate controlled release of the drug into the body. Common types of polymer coated drug eluting stents are disclosed by U.S. Pat. Nos. 6,774,278 and 6,730,064 issued to Ragheb entitled “Coated Implantable Medical Device.”

It has been postulated that the presence of this polymer contributes to thrombosis due to delamination. It is thought that over time, the protective polymer may separate from the bare metal or substrate, resulting in sharp peaks or edges that come in direct contact with red blood cells, the result of which is thrombosis, causing serious illness or death in the patient. Stents have been designed that do not include a permanent polymer, like BSI biodegradable PLLA. Some stent designs have moved towards the polymerless altogether such as surface textured stents or biocompatible oil coatings.

To increase the drug loading capacity, stents can be engineered to have roughened surfaces. Rough surfaces on the stent provide for peaks and valleys which increase the total surface area of the stent thereby increasing the amount of API that may be associated with the stent. Roughening of the surface of a stent is accomplished in a number of ways, such as sintering, as disclosed in U.S. Pat. No. 5,843,172 issued to Yan entitled “Porous Medical Stent.” Surface roughness is also achieved by abrasive techniques such as sandblasting and reductive acid etching as disclosed in European patent No. 0806212 issued to Leitao entitled “Device For Incorporation and Release of Biologically Active Agents.” Roughening of a stent surface can also be achieved pressing indentations directly onto the device as disclosed in U.S. Pat. No. 7,055,237 Issued to Thomas entitled “Method of Forming a Drug Eluting Stent” or using the common metal working techniques of shot peening or laser peening. A stent having a mechanical anchoring layer is described in co-owned U.S. Publication No. 2006/0069427. However, the stent and catheter crossing profile serve as physical limitations for the thickness of coatings. A problem encountered with rough stents is that the crossing profile of the stent and catheter must be limited to a thickness that is narrow enough to pass through an occluded artery.

In light of the complications associated with stent therapy, it would be desirable to develop a stent that will have the increased surface area of a rough stent which can be manufactured in such a way as to maximize structural integrity and drug loading capacity. Further, it would be desirable to develop a polymerless stent that is capable of delivering API to decrease or eliminate the risk the risk of late stent thrombosis. Finally, it is desirable to develop a stent that maximizes drug loading capacity while at the same time minimizing the total thickness of the stent-catheter crossing profile.

SUMMARY

The present embodiments solve one or more of the foregoing problems by providing a medical device such as a stent and method by which a drug eluting stent is treated that will decrease the crossing profile thickness without compromising structural integrity. The disclosed embodiments also maximize drug loading capacity and/or increase fatigue resistance.

In one aspect, a nonpolymeric therapeutic agent eluting stent is provided. Preferably, the stent includes at least a portion of at least one surface having a textured or abraded microstructure. In a preferred embodiment, the therapeutic agent is applied to at least the textured portion of the stent surface.

In another aspect, methods for preparing a stent with at least one “roughened” surface are disclosed. In one embodiment, the method includes crimping a bare metal stent into a hydrocarbon film layer which creates a mask for at least one of the inner layer and sides of the stent. The outer surface is then treated with an abrasive, and the masking layer is subsequently dissolved or otherwise removed. Preferably, the stent is then sonicated, cleaned and passivated according to ASTM standards.

In another embodiment, the stent surface is treated by the process of peening. The untreated stent is clamped on to a mandrel and roughening is achieved by pressing metal particles called shot onto the stent surface using plates or rollers. Roughness may also be achieved by blasting shot at the stent surface such as by jet blasting. In another embodiment, surface roughness can also be accomplished in a similar manner that employs a laser rather than shot.

In yet another embodiment, the stent is treated by pneumatic or hydraulic press to produce the roughened surface. The untreated stent is affixed to a mandrel and a pattern is stamped onto its surface by a pneumatic or hydraulic press. In one embodiment, the pattern is predetermined. In another embodiment, the pneumatic or hydraulic press is computer controlled. An advantage of the press method is its ability to disrupt microcrystalline structures in the stent body to increase the stent body\'s fatigue resistance.

In another embodiment, the entire length of the stent, for example 2.5 M, is treated before it is cut into the desired stent lengths. The entire stent length is attached to a mandrel and then treated via one of the methods disclosed.

In still a further embodiment, a stent is coated with an active pharmaceutical ingredient (API) or an API and polymer combination. The coating may be achieved via spraying the desired drug or drug/polymer combination directly on to the stent surface. Further, coating the stent with the desired chemical may be achieved by dipping the stent into a solution of the desired API coating. In yet another embodiment, the stent is coated with an API or API/polymer combination abluminally by automated pipetting.

These and other aspects and embodiments of the present invention will become better apparent in view of the detailed description in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description and the accompanying drawings wherein:

FIG. 1 is a scanned image of an endovascular stent having a metal filament body;

FIG. 2A is a scanning electron micrograph of an abraded stent surface;

FIG. 2B is a scanning electron micrograph of the surface of FIG. 2A showing quantification of peaks generated on the stent surface after abrasion;

FIG. 2C is a scanning electron micrograph of the surface of FIG. 2A showing quantification of valleys generated on the stent surface after abrasion;



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Prosthesis (i.e., artificial body members), parts thereof, or aids and accessories therefor
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stats Patent Info
Application #
US 20120029626 A1
Publish Date
02/02/2012
Document #
13206697
File Date
08/10/2011
USPTO Class
623/142
Other USPTO Classes
427/214
International Class
/
Drawings
24


Restenosis


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