This invention relates to stent mandrel fixtures or supports used during the process of coating stents.
Blood vessel occlusions are commonly treated by mechanically enhancing blood flow in the affected vessels, such as by employing a stent. Stents act as scaffoldings, functioning to physically hold open and, if desired, to expand the wall of affected vessels. Typically stents are capable of being compressed, so that they can be inserted through small lumens via catheters, and then expanded to a larger diameter once they are at the desired location. Examples in the patent literature disclosing stents include U.S. Pat. No. 4,733,665 issued to Palmaz, U.S. Pat. No. 4,800,882 issued to Gianturco, and U.S. Pat. No. 4,886,062 issued to Wiktor.
Stents are used not only for mechanical intervention but also as vehicles for providing pharmacological therapy. Pharmacological therapy can be achieved by medicating the stents. Medicated stents provide for the local administration of a therapeutic substance at the diseased site. Local delivery of a therapeutic substance is a preferred method of treatment because the substance is concentrated at a specific site and thus smaller total levels of medication can be administered in comparison to systemic dosages that often produce adverse or even toxic side effects for the patient.
One method of medicating a stent 10 involves the use of a polymeric carrier coated onto the surface of the stent 10. A composition including a solvent, a polymer dissolved in the solvent, and a therapeutic substance dispersed in the blend is applied to the stent 10 by immersing the stent 10 in the composition or by spraying the composition onto the stent 10. The solvent is allowed to evaporate, leaving on the surfaces a coating of the polymer and the therapeutic substance impregnated in the polymer.
The dipping or spraying of the composition onto the stent can result in a complete coverage of all stent surfaces, i.e., both luminal and abluminal surfaces, with a coating. However, from a therapeutic standpoint, drugs need only be released from the abluminal stent surface, and possibly the sidewalls. Moreover, having a coating on the luminal surface of the stent can have a detrimental impact on the stent's deliverability as well as the coating's mechanical integrity. A polymeric coating can increase the coefficient of friction between the stent and the delivery balloon. Additionally, some polymers have a “sticky” or “tacky” consistency. If the polymeric material either increases the coefficient of friction or adheres to the catheter balloon, the effective release of the stent from the balloon after deflation can be compromised. Adhesive, polymeric stent coatings can also experience extensive balloon sheer damage post-deployment, which could result in a thrombogenic luminal stent surface. Accordingly, there is a need to eliminate or minimize the amount of coating that is applied to the inner surface of the stent. Reducing or eliminating the polymer from the stent luminal surface also means a reduction in total polymer load, which is a desirable goal for optimizing long-term biocompatibility of the device.
A method for preventing the composition from being applied to the inner surface of the stent is by placing the stent over a mandrel that fittingly mates within the inner diameter of the stent. A tubing can be inserted within the stent such that the outer surface of the tubing is in contact with the inner surface of the stent. A tubular mandrel that makes contact with the inner surface of the stent can cause coating defects. A high degree of surface contact between the stent and the supporting apparatus can provide regions in which the liquid composition can flow, wick, and collect as the composition is applied to the stent. As the solvent evaporates, the excess composition hardens to form excess coating at and around the contact points between the stent and the supporting apparatus. Upon removal of the coated stent from the supporting apparatus, the excess coating may stick to the apparatus, thereby removing some of the coating from the stent and leaving bare areas. Alternatively, the excess coating may stick to the stent, thereby leaving excess coating composition as clumps or pools on the struts or webbing between the struts.
Accordingly, there is a tradeoff when the inner surface of the stent is masked in that coating defects such as pools and clumps can be formed on the stent. There is a need for eliminating or at least minimizing the coating that is formed on the inner surface of the stent as well as coating defects that are formed on the stent struts or between the stent struts caused by the high degree of surface contact between the stent and the mandrel. A mandrel design is needed that addresses these concerns.
A stent mandrel support to support a stent during application of a coating substance to the stent is provided, comprising a first member to contact a first end of the stent; a second member to contact, a second end of the stent; and a third member connecting the first member to the second member and extending through a longitudinal bore of the stent, the third member shaped and/or sized to eliminate or substantially prevent a coating from being formed on a luminal surface of the stent.
A mandrel to support a stent during application of a coating substance to a stent is provided, comprising a member to penetrate at least partially into a longitudinal bore of a stent during the application of a coating substance, the member including outward projecting walls, the length of at least one of the walls being not less than 25% of the length of the stent.
A mandrel to support a stent during the application of a coating composition to the stent is provided, comprising a mandrel body capable of being inserted at least partially into a longitudinal bore of a stent and a spiral wall circumscribing the mandrel body.
A mandrel to support a stent during the application of a coating composition to the stent is provided, comprising a mandrel body capable of being inserted at least partially into a longitudinal bore of a stent, wherein the mandrel body or a segment thereof is defined by a shape selected from the group consisting of configuration 2, 3, 4, 5, 6 or 7—as defined in the detailed description.
A mandrel to support a stent during application of a coating substance to a stent is provided comprising a member to penetrate at least partially into a longitudinal bore of a stent during the application of a coating substance, the member including 3 pairs of opposing parallel sides.
A mandrel to support a stent during application of a coating substance to a stent is provided comprising a member to penetrate at least partially into a longitudinal bore of a stent during the application of a coating substance, the member including 6 non-parallel sides.
A mandrel to support a stent during application of a coating substance to a stent is provided comprising a core section having at least three sides and a wall extending from each of the sides in an outwardly direction.
A mandrel to support a stent during application of a coating substance to a stent is provided comprising a member to penetrate at least partially into a longitudinal bore of a stent during the application of a coating substance, the member including outward projecting walls disposed around the circumference of the mandrel, wherein the wall converge with their neighboring walls at an angle.
A method is also provided to coat a stent using the embodiments of the mandrel of the present invention.
Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.
The following description is provided to enable any person having ordinary skill in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to the embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles, features and teachings disclosed herein.
The embodiment of the invention minimize the surface contact between the stent and the mandrel support so as to reduce or prevent coating defect on the stent. It is believed that the embodiments of the invention can also prevent a coating from being formed on the inner surface of the stent or reduce the amount of coating that is formed on the inner surface of the stent. This reduces the total polymer load on the stent 10, thereby improving long-term biocompatibility and ensuring that most of the coating is on the abluminal surface where it provides the most benefit. Further, problematic interactions between a delivery mechanism (e.g., delivery balloon) and the stent luminal surface are eradicated, thereby increasing the ease of stent deliverability.
The term inner diameter of stent is defined as the inner diameter of the stent as measured when positioned on the support 20. Accordingly, if the stent is pre-expanded partially when positioned on the support 20, the measurement would be taken in the partial pre-expansion state. The partial pre-expansion of a stent allows for the spaces between the struts to increase, thereby preventing or reducing the formation of “cobwebs.” However, it would also allow for the composition to contact the inner surface of the stent. Accordingly, there is a tradeoff when expanding the stent prior to the application of the coating composition.
The outer diameter of the mandrel 24 can be smaller than the inner diameter of the stent 10 so as to prevent the outer surface of the mandrel 24 from making contact with the luminal surface of the stent 10. A sufficient clearance between the outer surface of the mandrel 24 and the luminal surface of the stent 10 should be provided to prevent the mandrel 24 from obstructing the pattern of the stent body during the coating process. However, the outer diameter of the mandrel 24 should also be large enough to substantially shield the luminal surface of the stent 10 from spray coating. In other words, spray that would normally pass through the abluminal surface of the stent 10 and impact the luminal surface of the stent 10 will instead impact and coat the mandrel 24, as will be discussed in further detail below in conjunction with
The lock member 26 includes a coning end portion 42 having an inwardly tapered angle φ2. Angle φ2 can be the same as or different than the above-described angle φ1. The coning end portion 42 supports the stent 10 at a second end during a coating process. A second end 44 of the mandrel 24 can be permanently affixed to the lock member 26 if the end 40 is disengagable from the support member 22. Alternatively, in accordance with another embodiment, the mandrel 24 can have a threaded second end 44 for screwing into a bore 46 of the lock member 26. The bore 46 can be of any suitable depth that would allow the lock member 26 to be incrementally moved closer to the support member 22. The bore 46 can also extend completely through the lock member 26. Accordingly, stents 10 of any length can be securely pinched between the support and the lock members 22 and 26. In accordance with yet another embodiment, a non-threaded second end 44 and bore 46 combination is employed such that the second end 44 can be press-fitted or friction-fitted within the bore 46 to prevent movement of the stent 10 on the stent mandrel support 20.
In order to reduce coating defects at the point of contact between the stent 10 and the ends 36 and 42, the ends 36 and 42 may be coated with or made of one or more polymeric materials having less adhesive force with the coating substance than the coating substance with the stent. Examples of suitable polymeric materials include poly (tetrafluor ethylene) (e.g., Teflon®), fluorinated ethylene propylene, poly (vinylidene fluoride), poly (para-xylyene), polyamide (Nylon), polyolefins (e.g., high density poly (ethylene) and poly (propylene)), and polyacetal (DELRIN®). Of course the material used depends on the composition that is applied to the stent and the material from which the stent is made.
During a coating process, a sprayed composition 55 is sprayed onto the stent 10. The spray composition 55 impacts and coats the abluminal surface of the stent 10. In addition, some of the spray composition 55 passes through the gaps of the scaffolding network and impacts the body 50A, which acts to block the spray composition 55 from impacting, and therefore coating, the luminal surface of the stent 10.
The components of the coating substance or composition 55 can include a solvent or a solvent system comprising multiple solvents; a polymer or a combination of polymers; and optionally a therapeutic substance or a drug or a combination of drugs.
Representative examples of polymers that can be used to coat a stent or medical device include ethylene vinyl alcohol copolymer (commonly known by the generic name EVOH or by the trade name EVAL); poly(hydroxyvalerate); poly(L-lactic acid); polycaprolactone; poly(lactide-co-glycolide); poly(glycerol-sebacate); poly(hydroxybutyrate); poly(hydroxybutyrate-co-valerate); polydioxanone; polyorthoester; polyanhydride; poly(glycolic acid); poly(D,L-lactic acid); poly(glycolic acid-co-trimethylene carbonate); polyphosphoester; polyphosphoester urethane; poly(amino acids); cyanoacrylates; poly(trimethylene carbonate); poly(iminocarbonate); copoly(ether esters) (e.g. PEO/PLA); polyalkylene oxalates; polyphosphazenes; biomolecules, such as fibrin, fibrinogen, cellulose, starch, collagen and hyaluronic acid; polyurethanes; silicones; polyesters; polyolefins; polyisobutylene and ethylene-alphaolefin copolymers; acrylic polymers and copolymers; vinyl halide polymers and copolymers, such as polyvinyl chloride; polyvinyl ethers, such as polyvinyl methyl ether; polyvinylidene halides, such as polyvinylidene fluoride and polyvinylidene chloride; polyacrylonitrile; polyvinyl ketones; polyvinyl aromatics, such as polystyrene; polyvinyl esters, such as polyvinyl acetate; copolymers of vinyl monomers with each other and olefins, such as ethylene-methyl methacrylate copolymers, acrylonitrilestyrene copolymers, ABS resins, and ethylene-vinyl acetate copolymers; polyamides, such as Nylon 66 and polycaprolactam; alkyd resins; polycarbonates; polyoxymethylenes; polyimides; polyethers; epoxy resins; polyurethanes; rayon; rayon-triacetate; cellulose; cellulose acetate; cellulose butyrate; cellulose acetate butyrate; cellophane; cellulose nitrate; cellulose propionate; cellulose ethers; and carboxymethyl cellulose.
“Solvent” is defined as a liquid substance or composition that is compatible with the polymer and is capable of dissolving the polymer at the concentration desired in the composition. Examples of solvents include, but are not limited to, dimethylsulfoxide, chloroform, acetone, water (buffered saline), xylene, methanol, ethanol, 1-propanol, tetrahydrofuran, 1-butanone, dimethylformamide, dimethylacetamide, cyclohexanone, ethyl acetate, methylethylketone, propylene glycol monomethylether, isopropanol, isopropanol admixed with water, N-methylpyrrolidinone, toluene, and mixtures and combinations thereof.
The therapeutic substance or drug can be for inhibiting the activity of vascular smooth muscle cells. More specifically, the active agent can be aimed at inhibiting abnormal or inappropriate migration and/or proliferation of smooth muscle cells for the inhibition of restenosis. The drug can also include any substance capable of exerting a therapeutic or prophylactic effect. For example, the agent can be for enhancing wound healing in a vascular site or improving the structural and elastic properties of the vascular site. Examples of agents include antiproliferative substances such as actinomycin D, or derivatives and analogs thereof (manufactured by Sigma-Aldrich 1001 West Saint Paul Avenue, Milwaukee, Wis. 53233; or COSMEGEN available from Merck). Synonyms of actinomycin D include dactinomycin, actinomycin IV, actinomycin I1, actinomycin X1, and actinomycin C1. The active agent can also fall under the genus of antineoplastic, antiinflammatory, antiplatelet, anticoagulant, antifibrin, antithrombin, antimitotic, antibiotic, antiallergic and antioxidant substances. Examples of such antineoplastics and/or antimitotics include paclitaxel (e.g. TAXOL® by Bristol-Myers Squibb Co., Stamford, Conn.), docetaxel (e.g. Taxotere®, from Aventis S.A., Frankfurt, Germany) methotrexate, azathioprine, vincristine, vinblastine, fluorouracil, doxorubicin hydrochloride (e.g. Adriamycin® from Pharmacia & Upjohn, Peapack N.J.), and mitomycin (e.g. Mutamycin® from Bristol-Myers Squibb Co., Stamford, Conn.). Examples of such antiplatelets, anticoagulants, antifibrin, and antithrombins include sodium heparin, low molecular weight heparins, heparinoids, hirudin, argatroban, forskolin, vapiprost, prostacyclin and prostacyclin analogues, dextran, D-phe-pro-arg-chloromethylketone (synthetic antithrombin), dipyridamole, glycoprotein IIb/IIIa platelet membrane receptor antagonist antibody, recombinant hirudin, and thrombin inhibitors such as Angiomax™ (Biogen, Inc., Cambridge, Mass.). Examples of such cytostatic or antiproliferative agents include angiopeptin, angiotensin converting enzyme inhibitors such as captopril (e.g. Capoten® and Capozide® from Bristol-Myers Squibb Co., Stamford, Conn.), cilazapril or lisinopril (e.g. Prinivil® and Prinzide® from Merck & Co., Inc., Whitehouse Station, N.J.); calcium channel blockers (such as nifedipine), colchicine, fibroblast growth factor (FGF) antagonists, fish oil (omega 3-fatty acid), histamine antagonists, lovastatin (an inhibitor of HMG-CoA reductase, a cholesterol lowering drug, brand name Mevacor® from Merck & Co., Inc., Whitehouse Station, N.J.), monoclonal antibodies (such as those specific for Platelet-Derived Growth Factor (PDGF) receptors), nitroprusside, phosphodiesterase inhibitors, prostaglandin inhibitors, suramin, serotonin blockers, steroids, thioprotease inhibitors, triazolopyrimidine (a PDGF antagonist), and nitric oxide. An example of an antiallergic agent is permirolast potassium. Other therapeutic substances or agents which may be appropriate include alpha-interferon, genetically engineered epithelial cells, dexamethasone, rapamycin, and structural derivatives and functional analogues of rapamycin.
In another embodiment, a body 50C can have configuration as shown in
It should be noted that in some embodiments the mandrel 24 or the body 50 can contact the inner stent surface. As best illustrated by
In lieu of spike shaped walls forming a “star” shaped cross section, the spikes could be curved such that the cross section of the body 50 would resemble a 4 leaf clover, as depicted in
In the conducted experiment, the process parameters are listed in Table I below. PEA Benzyl Ester (300 μg) was coated onto 12 mm small VISION stents (available from Guidant Corp.) from a 2 wt % PEA Benzyl Ester in ethanol (200 proof) formulation. Coating flow rates were approximately 20 μg/pass. The stents were oven baked at 50° C. for 1 hour. Results indicated that the abluminal stent coatings were not affected using a stent mandrel support having a section 50A with diameter of 0.061 and 0.0625 inches. However, luminal stent coating was significantly reduced as the diameter of the section 50A is increased. The larger diameter pin was able to “shield” the inner diameter stent surface from much of the atomized spray solution.
While particular embodiments of the present invention have been shown and described, it will be obvious to one of ordinary skill in the art that changes and modifications can be made without departing from this invention in its broader aspects. For example, after application of the coating to the abluminal surface of the stent 10 as described above, the luminal surface of the stent 10 can be coated with a different coating via spray coating, electroplating or other technique. Therefore, the appended claims are to encompass within their scope all such changes and modifications as fall within the true spirit and scope of this invention.
Number | Name | Date | Kind |
---|---|---|---|
4629563 | Wrasidlo | Dec 1986 | A |
4733665 | Palmaz | Mar 1988 | A |
4762128 | Rosenbluth | Aug 1988 | A |
4800882 | Gianturco | Jan 1989 | A |
4846791 | Hattler et al. | Jul 1989 | A |
4886062 | Wiktor | Dec 1989 | A |
4906423 | Frisch | Mar 1990 | A |
5037427 | Harada et al. | Aug 1991 | A |
5171445 | Zepf | Dec 1992 | A |
5188734 | Zepf | Feb 1993 | A |
5229045 | Soldani | Jul 1993 | A |
5234457 | Andersen | Aug 1993 | A |
5389106 | Tower | Feb 1995 | A |
5537729 | Kolobow | Jul 1996 | A |
5611775 | Machold et al. | Mar 1997 | A |
5624411 | Tuch | Apr 1997 | A |
5628786 | Banas et al. | May 1997 | A |
5674208 | Berg et al. | Oct 1997 | A |
5772864 | Møller et al. | Jun 1998 | A |
5788626 | Thompson | Aug 1998 | A |
5820917 | Tuch | Oct 1998 | A |
5823996 | Sparks | Oct 1998 | A |
5833659 | Kranys | Nov 1998 | A |
5855598 | Pinchuk | Jan 1999 | A |
5865814 | Tuch | Feb 1999 | A |
5895407 | Jayaraman | Apr 1999 | A |
5897911 | Loeffler | Apr 1999 | A |
5922393 | Jayaraman | Jul 1999 | A |
5935135 | Bramfitt et al. | Aug 1999 | A |
5948018 | Dereume et al. | Sep 1999 | A |
6010573 | Bowlin | Jan 2000 | A |
6045899 | Wang et al. | Apr 2000 | A |
6056993 | Leidner et al. | May 2000 | A |
6059714 | Armini et al. | May 2000 | A |
6120847 | Yang et al. | Sep 2000 | A |
6126686 | Badylak et al. | Oct 2000 | A |
6153252 | Hossainy et al. | Nov 2000 | A |
6156373 | Zhong et al. | Dec 2000 | A |
6214115 | Taylor et al. | Apr 2001 | B1 |
6245099 | Edwin et al. | Jun 2001 | B1 |
6258121 | Yang et al. | Jul 2001 | B1 |
6279368 | Escano et al. | Aug 2001 | B1 |
6322847 | Zhong et al. | Nov 2001 | B1 |
6364903 | Tseng et al. | Apr 2002 | B2 |
6387118 | Hanson | May 2002 | B1 |
6521284 | Parsons et al. | Feb 2003 | B1 |
6527863 | Pacetti et al. | Mar 2003 | B1 |
6565659 | Pacetti et al. | May 2003 | B1 |
6572644 | Moein | Jun 2003 | B1 |
6605154 | Villareal | Aug 2003 | B1 |
6673154 | Pacetti et al. | Jan 2004 | B1 |
6695920 | Pacetti et al. | Feb 2004 | B1 |
7083642 | Sirhan et al. | Aug 2006 | B2 |