Coating processes – Medical or dental purpose product; parts; subcombinations;... – Implantable permanent prosthesis
Reexamination Certificate
2001-06-29
2004-09-07
Beck, Shrive P. (Department: 1762)
Coating processes
Medical or dental purpose product; parts; subcombinations;...
Implantable permanent prosthesis
C427S002250, C427S002260, C427S002270, C427S002280, C427S002290, C427S002300, C427S487000, C427S488000, C427S489000, C427S490000, C427S491000, C427S533000, C427S534000, C427S535000, C427S536000, C427S372200
Reexamination Certificate
active
06787179
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to coatings and sterilization of coatings for devices with a medical use.
2. Description of the Related Art
Many polymeric materials can be used as medical device and implant fabrication materials. To improve the biocompatibility of these materials, surface modifications and coatings are used to reduce thrombosis or rejection. The modification or coating of these materials require several processing steps to accomplish the material coating. Substrates modified by each of these methods also require a sterilization method to finalize the product for use by the manufacturer. This introduces the issue of stability of the modified surface under the sterilization process, as the coating materials may not be compatible with traditional sterilization methods.
Different methods of surface modification have been documented in the literature for the purpose of favorable host-material response. Several U.S. patent documents provide means to coat biomedical devices, particularly those in contact with blood such as stents, but do not address the problem of subsequent sterilization (U.S. Pat. Nos. 4,656,083; 5,034,265; 5,132,108; 5,244,654; and 5,409,696) Palmaz et al, in a review of intravascular stents, is skeptical of the use of stent coatings (Palmaz, J., F. Rivera and C. Encamacion. Intravascular Stents,
Adv. Vasc. Surg.,
1993, 1:107-135). However, Kocsis et al. report that the use of heparin-coated stents was effective to reduce thrombogenicity of the stent surface (Kocsis, J., G. Llanos and E. Holmer. Heparin-Coated Stents,
J. of Long-Term Effects of Medical Implants,
2000, 10 19-45)
Typical modifications include hydrophilic and/or hydrogel coatings such as polyvinyl pyrrolidone (PVP), polyethylene glycol (PEG), or Hyaluronic acid (HA), on the surface of cardiovascular implants (stents and pacemakers) or indwelling medical devices, topical wound healing applications, contact lenses, intraocular lenses, etc. Hydrophobic or lubricious coatings are used for medical devices such as coronary or neurovascular guidewires, sutures, needles, catheters and trocars. Bio-active coatings are used for directed cell response such as cell adhesion molecules (CAM, such as RGD (amino acid sequence Arg-Glu-Asp), laminin, collagen, etc.) in tissue engineering applications or adhesion prevention coatings to be used on medical devices such as vena cava filters or small diameter vascular grafts. Coating material also include infection resistance coatings or antimicrobial containing coating. Some coatings also provide for sustained drug release such as sustained release of drug from stents, or as a hydrophobic overcoat to extend the release time of a drug loaded depot. Bio-active coatings containing therapeutic agents such as heparin, phosphoryl choline (PC), urokinase, etc., are used for antithrombogenic properties.
The coatings can be used to deliver therapeutic and pharmaceutic agents such as, but not limited to: antiproliferative/antimitotic agents including natural products such as vinca alkaloids (i.e. vinblastine, vincristine, and vinorelbine), paclitaxel, epidipodophyllotoxins (i.e. etoposide, teniposide), antibiotics (dactinomycin (actinomycin D) daunorubicin, doxorubicin and idarubicin), anthracyclines, mitoxantrone, bleomycins, plicamycin (mithramycin) and mitomycin, enzymes (L-asparaginase which systemically metabolizes L-asparagine and deprives cells which don't have the capacity to synthesize their own asparagine; antiproliferative/antimitotic alkylating agents such as nitrogen mustards (mechlorethamine, cyclophosphamide and analogs, melphalan, chlorambucil), ethylenimines and methylmelamines (hexamethylmelamine and thiotepa), alkyl sulfonates-busulfan, nitrosoureas (carmustine (BCNU) and analogs, streptozocin), trazenes—dacarbazinine (DTIC); antiproliferative/antimitotic antimetabolites such as folic acid analogs (methotrexate), pyrimidine analogs (fluorouracil, floxuridine, and cytarabine), purine analogs and related inhibitors (mercaptopurine, thioguanine, pentostatin and 2-chlorodeoxyadenosine {cladribine}); platinum coordination complexes (cisplatin, carboplatin), procarbazine, hydroxyurea, mitotane, aminoglutethimide; hormones (i.e.estrogen); Anticoagulants (heparin, synthetic heparin salts and other inhibitors of thrombin); fibrinolytic agents (such as tissue plasminogen activator, streptokinase and urokinase), aspirin, dipyridamole, ticlopidine, clopidogrel, abciximab; antimigratory; antisecretory (breveldin); anti-inflammatory: such as adrenocortical steroids (cortisol, cortisone, fludrocortisone, prednisone, prednisolone, 6&agr;-methylprednisolone, triamcinolone, betamethasone, and dexamethasone), non-steroidal agents (salicylic acid derivatives i.e. aspirin; para-aminophenol derivatives i.e. acetominophen; Indole and indene acetic acids (indomethacin, sulindac, and etodalac), heteroaryl acetic acids (tolmetin, diclofenac, and ketorolac), arylpropionic acids (ibuprofen and derivatives), anthranilic acids (mefenamic acid, and meclofenamic acid), enolic acids (piroxicam, tenoxicam, phenylbutazone, and oxyphenthatrazone), nabumetone, gold compounds (auranofin, aurothioglucose, gold sodium thiomalate); immunosuppressive: (cyclosporine, tacrolimus (FK-506), sirolimus (rapamycin), azathioprine, mycophenolate mofetil); Angiogenic: vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF); nitric oxide donors; anti-sense oligo nucleotides and combinations thereof.
Coating may be formulated by mixing one or more therapeutic agents with the polymeric coating mixture. The therapeutic agent may be present as a liquid, a finely divided solid, or any other appropriate physical form. Optionally, the coating mixture may include one or more additives, e.g., nontoxic auxiliary substances such as diluents, carriers, excipients, stabilizers or the like. Other suitable additives may be formulated with the polymer and pharmaceutically active agent or compound. For example, hydrophilic polymer may be added to a biocompatible hydrophobic coating to modify the release profile, or a hydrophobic polymer may be added to a hydrophilic coating to modify the release profile. One example would be adding a hydrophilic polymer selected from the group consisting of polyethylene oxide (PO), PVP, PEG, carboxymethyl cellulose, and hydroxymethyl cellulose to a hydrophobic (co)polymer coating to modify the release profile. Appropriate relative amounts can be determined by monitoring the in vitro and/or in vivo release profiles for the therapeutic agents.
Methods for surface modification typically include a surface activation step followed by the coupling of the desired molecule. Surface activation is usually achieved by an energy assisted gas phase reaction (plasma, pulsed plasma, flow discharge reactive chemistry (FDRC), corona discharge, etc.) and/or activating the substrate with a highly reactive leaving group (N—OH succinimide, imidizole, etc.); Functionalization of the surface with self-assembly molecules (SAM, functional silanes and thiols); Controlled hydrolysis of the esters and amides at the surface (polyethylene terephthalate (PET), polylactic acid (PLA), polyglycolic acid (PGA), etc.). Coupling reactions are typically accomplished by carbodiidimide chemistry, reductive amination, malemide-thiol reactions, etc.
Photochemical surface modifications are usually preferred since this method typically does not require a prior surface activation step. Arylketone based chemistry, azide chemistry, acrylate chemistry are key examples.
Sterilization
Most of the coating methods require several processing steps to accomplish the material coating. Substrates modified by each of these methods also require a sterilization method to finalize the product for use by the manufacturer. This introduces the issue of stability of the modified surface under the sterilization process. Conventional sterilization methods such as steam, radiation, and ethylene oxide negatively impact the activity of the coating. Further, radiation (
Hossainy Syed
Hui Henry K.
Melican Mora C.
Roller Mark B.
Timm Debra A.
Beck Shrive P.
Ethicon Inc.
Kolb Michener Jennifer
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