Coating processes – Medical or dental purpose product; parts; subcombinations;... – Device for creating or holding open an unnatural opening in...
Reexamination Certificate
2001-06-28
2004-01-06
Beck, Shrive P. (Department: 1762)
Coating processes
Medical or dental purpose product; parts; subcombinations;...
Device for creating or holding open an unnatural opening in...
C427S002100, C427S002240, C427S002250, C427S002300, C427S508000, C427S487000, C427S421100
Reexamination Certificate
active
06673385
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for coating stents.
2. Description of the Background
Stents act as scaffoldings, functioning to physically hold open and, if desired, to expand the wall of a passageway. Typically stents are capable of being compressed, so that they can be inserted through small vessels via catheters, and then expanded to a larger diameter once they are at the desired location. Mechanical intervention via stents has reduced the rate of restenosis; restenosis, however, is still a significant clinical problem. Accordingly, stents have been modified not only to perform as a mechanical scaffolding, but also to provide biological therapy.
Biological therapy can be achieved by medicating the stents. Medicated stents provide for the local administration of a therapeutic substance at the diseased site. In order to provide an efficacious concentration to the treated site, systemic administration of such medication often produces adverse or toxic side effects for the patient. Local delivery is a preferred method of treatment in that smaller total levels of medication are administered in comparison to systemic dosages, but are concentrated at a specific site. Local delivery thus produces fewer side effects and achieves more favorable results.
A common method of medicating a stent is by depositing a polymeric coating, impregnated with the therapeutic substance, on the surface of the stent. A polymer dissolved in a solvent is applied to the stent. A therapeutic substance can be dissolved or dispersed in the composition. The solvent is allowed to evaporate to form the coating. The application of the composition can be performed by spraying the composition on the stent or immersing the stent in the composition. A problem associated with the application of a polymeric solution includes coating defect such as “cob webs” and “pool webs.” “Cob webs” are defined as the gathering of the polymeric coating between the stent struts once the solvent has been removed. “Pool webs” are clumps or pools of polymer on the struts. “Cob webs” and “pool webs” are caused by high viscosities associated with the composition and the surface tension of the polymer and the solvent. Moreover, increasing the quantity of the polymer applied to the stent, so as to increase the drug loading of the stent, further promulgates the development of such defects. Accordingly, a method is needed to reduce or significantly eliminate coating defects on a stent.
SUMMARY
A method of forming a polymeric coating on a stent is provided. In one embodiment, the method can comprise the acts of applying a monomer or a combination of monomers to the stent and initiating polymerization of the monomer or combination of monomers to form a polymeric coating on the stent. The act of applying can be conducted by spraying the monomer or monomers at the stent. The polymerization can be initiated by radical chain reaction or step-function reaction. The polymerization can be initiated by the inclusion of a photochemical and exposure of the stent to a light energy source or by the inclusion of a thermal initiator and exposure of the stent to a thermal energy source. In one embodiment the monomer or monomers can be in a liquid phase or can be added to a solvent or a combination of solvents to effect dissolution of the monomer(s). The method can also include applying an active agent to the stent. The active agent can be applied separately or added to the monomer or at least one of the monomers of the combination.
In accordance with another embodiment, a method of forming a polymeric coating on a stent is provided comprising spraying a radially expandable stent with a coating fluid, the fluid comprising a prepolymer and causing the prepolymer to react to form a polymeric coating on the stent. The fluid can optionally include an additive for increasing the viscosity of the fluid. The fluid can also include an active agent for the treatment of restenosis, or alternatively, the active agent can be applied in a separate application step.
In accordance with another embodiment a method of forming a polymeric coating for a stent is provided comprising applying an oligomer or a combination of oligomers to the stent; and initiating polymerization of the oligomer or combination of oligomers to form a polymeric coating for the stent.
In accordance with another embodiment a method of forming a polymeric coating for a stent is provided comprising applying a macromer or a combination of macromers to the stent; and initiating polymerization of the macromer or combination of macromer to form a polymeric coating for the stent.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Monomers or monomeric chemical compounds are generally defined as the building material from which a polymer is formed such as by step-function (condensation), radical chain (addition) polymerization, or ionic polymerization processes. Monomeric chemical compounds are to be distinguished from oligomers and macromonomers. Oligomers are defined as polymer intermediates containing relatively few structural units. Polymers having a reactive group at one end and intended for further reaction are called macromonomers, or in conventional abbreviation, macromers. Polymer or polymeric compounds are inclusive of homopolymers, copolymers, terpolymers etc., including random, alternating, block and graft variations thereof. The term “prepolymer” as used herein after is intended to include one or a combination of different monomers, oligomers, and macromers that are capable of forming a polymer. Should any of the prepolymers be in a solid phase at operating temperatures, e.g., ambient temperature and pressure, the prepolymer can be dissolved in a solvent system for application to a stent.
In accordance with one embodiment, a monomer or a combination of monomers can be applied to a stent for coating the stent. The monomer can be any chemical which can be polymerized to form a suitable, biocompatible coating on the stent. Examples of the monomer can include, but are not limited to, vinyl, acrylate and allyl compounds such as any monomer with one or more vinyl, acrylate or allyl double bonds. Specific examples of some suitable monomers include 2-hydroxyethyl methacrylate (HEMA); glycol methacrylate; methyl methacrylate; ethyl methacrylate; butyl methacrylate; sulfanato ethyl methacrylate; ethylene vinyl acetate; ethyl acrylate; acrylamide; urethane-acrylate; acrylamide-ethyl methacrylate; di-vinyl benzene; triethylene glycol divinyl ether; tri-methylol propane tri-acrylate; pentaerythritol tetra-acrylate; Bisphenol A ethoxylate diacrylate; allyl ether, di-allyl maleate; vinyledene fluoride; and tri-allyl isocyanurate. Additionally, unsaturated monomers such as cell adhesion promoting, non-fouling, or anti-restenotic monomers can be used to form the coating or as additives to be used in conjunction with other prepolymers. Examples include vitamin E methacrylate, phenoxyethylmethacrylate, dimethyl amino ethyl methacrylate, vinyl pyrrolidone, polyethylene glycol methacrylate, sulfonated Dextran, methacryloxy phosphoryl choline, methacrylate acid, acrloyl, and methacryloyl. The combination of different monomers can form polymers with properties suitable for drug impregnation and stent coating.
In accordance with another embodiment, an oligomer or combination of oligomers can be used to coat the stent. A representative example includes urethane-acrylate (e.g., Cognis 6892, formerly Henckel 12-892).
In accordance with another embodiment, a macromer or a combination of macromers can be used to coat the stent. Representative examples include, but are not limited to polyethylene glycol diacrylates and polycaprolactone diacrylate.
Subsequent to the application of the prepolymers, polymerization is induced to form a polymeric coating on the stent by, for example, photoinitiated polymerization reaction as is well understood by one of ordinary skill in the art. Briefly, light of short enough wavelength (e.g., 320-800 nm) or, in other words, high enough energy per qua
Ding Ni
Hossainy Syed F. A.
Millare Deborra Sanders
Advanced Cardiovascular Systems Inc.
Beck Shrive P.
Kolb Michener Jennifer
Squire Sanders & Dempsey L.L.P.
LandOfFree
Methods for polymeric coatings stents does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Methods for polymeric coatings stents, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Methods for polymeric coatings stents will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3255788