News Column

Patent Issued for Coated Medical Device and Method for Manufacturing the Same

June 18, 2014



By a News Reporter-Staff News Editor at Journal of Engineering -- According to news reporting originating from Alexandria, Virginia, by VerticalNews journalists, a patent by the inventors Austin, Michael (Tuam, IE); Robinson, Don (Framingham, MA); Boulais, Dennis R. (Danielson, CT); Kulkarni, Praveen (Worcester, MA); Freyman, Toby (Waltham, MA); Epstein, Samuel J. (Marlborough, MA); Naimark, Wendy (Boston, MA); Schwarz, Marlene (Auburndale, MA), filed on October 8, 2012, was published online on June 3, 2014.

The assignee for this patent, patent number 8739727, is Boston Scientific Scimed, Inc. (Maple Grove, MN).

Reporters obtained the following quote from the background information supplied by the inventors: "It has been proposed that a variety of medical conditions can be treated by introducing an insertable or implantable medical device having a coating for release of a biologically active material. For example, various types of drug-coated stents have been proposed for localized delivery of drugs to a body lumen. See U.S. Pat. No. 6,099,562 to Ding et al.

"However, the coatings for a medical device can exhibit problems of cracking especially when the device is exposed to harsh conditions, such as low temperatures and/or mechanical deformations. For example, a self-expanding stent must be contracted and loaded into a delivery sheath before delivering into a patient's body. To contract a self-expanding stent made of a shape-memory alloy, it must be chilled to be thermally induced into the Martenstic phase, in which the shape-memory alloy can be plastically deformed. In practice, the self-expanding stent is chilled to about -80.degree. to -100.degree. C. and then warmed to about -60.degree. to -20.degree. C. when it is contracted. However, the processing temperature about -60.degree. to -20.degree. C. is usually the same as or lower than the glass transition temperatures of many polymers. Therefore, when chilled to these temperatures, a polymer coating on the stent is in a condition like glass and particularly vulnerable to stress-cracking when the device is processed.

"The risk of cracking the coating is particularly high in certain parts of the coated stent, such as the apex regions of a zigzag strut configuration where the surface of the strut is greatly deformed by contraction of the stent as shown in FIGS. 1, 1a and 2. FIG. 1 shows a schematic view of a portion of a stent 10 having struts 11 in its expanded state. The apex regions of the zigzag strut configuration 12 are magnified in FIG. 1a. FIG. 2 shows a schematic view of the same apex regions 12 when the stent is in its contracted state and the cracks 13 in the coating that may occur at the apex regions. Cracks in the coating are undesirable because they can cause the coating to flake or separate from the coated surface of the device while the coated medical device is inside the body of a patient. Such separated or loose pieces of coating can cause emboli. Hence, there is a need for a coated medical device wherein a risk of cracks in the coating is reduced.

"Furthermore, when a medical device such as a stent is delivered to the implantation site, the coated surface of the medical device is often covered by a sheath to prevent the coating from being removed before the medical device is inserted and appropriately located inside the body. Also, if the coated surface of the medical device is self-expanding, a sheath is used to contract the portion so that the device can be inserted, such as in the case of a self-expanding stent. However, the sheath is likely to contact the coating located on the outermost portion of the coated surface. The coating material at such outermost portion may adhere to the sheath. When the sheath is withdrawn, the adhered coating may be torn or removed from the coated device. Therefore, there is a need for a coated medical device that avoids such undesired tearing of the coating.

"Also, the conventional methods for coating medical devices require encapsulating the device or coating entire surfaces of the device. However, in many medical devices, not all of the surfaces or the entirety of the surfaces of the medical device need to be coated. For instance, in medical devices having a tubular portion, such as a vascular stent, the inner surface of the tubular portion does not have to be coated with a coating containing a biologically active material that is used to treat only the body lumen wall that contacts the outer surface of the stent. This is because the inner surface of the stent does not come in contact with body-lumen wall and does not apply the biologically active material to the body-lumen wall. When all the surfaces of a medical device such as a stent, including surfaces that are not directly in contact with the body tissue of a patient, are coated with a composition comprising a biologically active material, more biologically active material is used than is needed. Thus, the patient may receive unnecessary exposure to the material. Also, manufacturing costs for the medical device may be needlessly increased by including unnecessary amounts of the biologically active material in the medical device.

"Moreover, if the medical device is an expandable stent, the coating on the sides of the struts may adhere to each other when the stent is placed in its contracted state. When the stent is expanded, the adhered coating may be removed from the struts. In addition, if the medical device is a balloon expandable stent, the coating on the inner surface of the stent has higher risk of damage because it directly contacts the balloon and is pressed by a balloon. Such damage is undesirable because the damaged coating may separate from the device while the device is inserted in a patient. Accordingly, there is a need for a method that can coat only the outer surface of a medical device or the surface that directly contacts the body tissue to be treated."

In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "The present invention is directed to a medical device comprising a structure. The structure has a thickness and a surface. The surface of the structure comprises at least one outermost portion and a plurality of depressions. These depressions occupy at least about 80% of the surface area of the surface. Also, at least one of the depressions contain a coating material. Preferably, a majority of the depressions contain coating material. The outermost portion of the surface is substantially free of any coating material. This coating material can contain a biologically active material and/or a polymer.

"Furthermore, the present invention relates to a method for manufacturing a medical device. In this method, a medical device having a surface is obtained. The surface of the medical device comprises at least one outermost portion and a plurality of depressions. The depressions occupy at least about 80% of the surface area of the surface. A coating material is applied to the surface of the medical device in a manner such that the outermost portion of the surface is substantially free of any coating material and the coating material is present in at least one of the depressions. The outermost portion may be made substantially free of the coating material by removing the coating material from the outermost portion.

"In addition, another embodiment of the invention involves a system and a method for manufacturing a medical device having at least a tubular portion, wherein the tubular portion has a surface. In this system a coating material is applied on a surface of a first roller. The coating material is then transferred from the first roller surface to the surface of the tubular structure. Also, if there is an excess amount of the coating material on the first roller surface, it can be removed, e.g., by a doctor blade, before the coating material is transferred to the surface of the tubular portion. Additionally, the method can involve a second roller. The coating material on the first roller surface is transferred onto a surface of a second roller. Then, the coating material is transferred from the second roller surface to the outer surface of the tubular portion.

"The present invention also pertains to a system for coating a medical device having a tubular portion with an outer surface. The system comprises a coating material source containing a coating material. The system also includes a roller having a surface, in which the roller is situated relative to the coating material source so that the coating material in the coating source can be transferred to the roller surface. Also, the roller is situated relative to the outer surface of the tubular portion so that the roller surface can transfer the coating material transferred to the roller surface onto the outer surface of the tubular portion. The system can further include a reservoir that continuously supplies the coating material source with coating material. In addition, the surface of the roller can comprise a plurality of grooves.

"In another embodiment, the system for coating a medical device comprises a coating material source containing a coating material, a first roller having a surface and a second roller having a surface. The first roller is situated relative to the coating material source so that the coating material in the coating material source can be transferred to the first roller surface. The first roller and second roller are situated relative to each other so that the first roller can transfer the coating material transferred to the first roller surface to the second roller surface. The second roller is situated relative to the tubular portion so that the second roller can transfer the coating material transferred to the second roller surface to the outer surface of the tubular portion. The surface of the second roller can be rougher than the surface of the first roller. Preferably, the first roller contacts the surface of the second roller and the surface of the second roller contacts the outer surface of the tubular portion. Also the system can include a mechanism for removing excess coating material from the surface of the first roller. Furthermore, the system can include an energy source for converting the coating material applied to the outer surface of the tubular portion into a coating.

"In yet another embodiment, the system comprises a coating material source containing a coating material; a first roller having a surface; a second roller having a surface; a third roller having a surface; and a flexible webbing material position around the second and third rollers. The first roller is situated relative to the coating material source so that the coating material can be transferred to the first roller surface. The first roller and webbing are situated relative to each other so that the first roller can transfer the coating material transferred to the first roller surface to the webbing. Additionally, the webbing is situated relative to the tubular portion so that the webbing can transfer the coating material transferred to the webbing to the outer surface of the tubular portion. Preferably, the webbing contacts the outer surface of the tubular portion.

"The present invention is also directed to a system for coating a medical device having a tubular portion with an outer surface in which the system comprises a roller having a surface and an applicator for applying an adhesion protein to the roller surface. The roller is situated relative to the tubular portion so that the roller can transfer the adhesion protein to the outer surface. The outer surface is exposed to a cell suspension and the adhesion protein can be transferred to the outer surface as the outer surface is simultaneously exposed to the cell suspension.

"Moreover, the present invention is directed to a lithographic method for coating a medical device having a tubular portion with an outer surface. The method comprises providing a layer of an unsolidified gel. A crosslinking agent is applied onto the outer surface of the tubular portion. The crosslinking agent is transferred from the outer surface of the tubular portion to the gel layer by rolling the tubular portion over the gel layer to form a crosslinked, planar replica of the outer surface onto the unsolidified gel to crosslink the unsolidified gel. An adhesive material is applied onto the outer surface of the tubular portion. The tubular portion is rolled over the gel in the same manner as the first time the tubular portion was rolled over the gel so that the crosslinked planar replica is aligned with and attaches to the outer surface of the tubular portion."

For more information, see this patent: Austin, Michael; Robinson, Don; Boulais, Dennis R.; Kulkarni, Praveen; Freyman, Toby; Epstein, Samuel J.; Naimark, Wendy; Schwarz, Marlene. Coated Medical Device and Method for Manufacturing the Same. U.S. Patent Number 8739727, filed October 8, 2012, and published online on June 3, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8739727.PN.&OS=PN/8739727RS=PN/8739727

Keywords for this news article include: Boston Scientific Scimed Inc.

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Source: Journal of Engineering


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