WO2003092791A2

WO2003092791A2 - Energetically-controlled delivery of biologically active material from an implanted medical device

Info

Publication number: WO2003092791A2
Application number: PCT/US2003/013966
Authority: WO
Inventors: Mark Hamm; Lou Barbato; Robert J. Crowley; Wendy Naimark; Hatal Patel
Original assignee: Scimed Life Systems, Inc.
Priority date: 2002-05-02
Filing date: 2003-05-02
Publication date: 2003-11-13
Also published as: AU2003228858A1; US20070010871A1; US20040030379A1; US7585320B2; AU2003228858A8; WO2003092791A3; US7101394B2

Abstract

A medical device and system capable of providing on-demand delivery of biologically active material to a body lumen patient, and a method of making such medical device. A first coating layer (40) having a biologically active material (45) and optionally a polymeric material is disposed on the surface of the medical device. A second coating layer (50) comprising magnetic particles (55) and a polymeric material is disposed on the first coating layer. The second coating layer, which is substantially free of a biologically active material, protects the biologically active material prior to delivery. The system includes the medical device and a source of energy, such as an electromagnetic or mechanical vibrational energy. When the patient is exposed to the energy source, the magnetic particles move out of the second coating layer and create channels therein through which the biologically active material can be released.

Description

ENERGETICALLY-CONTROLLED DELIVERY OF BIOLOGICALLY ACTIVE MATERIAL FROM AN IMPLANTED MEDICAL DEVICE RELATED APPLICATION

The present invention claims the benefit of U.S. Provisional Application No. 60/377,428, filed May 2, 2002.

FIELD OF THE INVENTION The present invention generally relates to medical devices capable of providing on-demand delivery of biologically active material to a patient. In particular, the invention is directed to medical devices comprising a biologically active material, which is released from the device when the biologically active material is needed by the patient. The biologically active material is released when the patient is exposed to an energy source, such as electromagnetic energy or mechanical vibrational energy. When electromagnetic energy is used the medical device should also comprise magnetic particles that facilitate the release ofthe biologically active material.

BACKGROUND OF THE INVENTION In order to treat a variety of medical conditions, insertable or implantable medical devices having a coating for release of a biologically active material have been used. For example, various types of drug-coated stents have been used for localized delivery of drugs to a body lumen. See U.S. Patent No. 6,099,562 to Ding et al. Such stents have been used to prevent, ter alia, the occurrence of restenosis after balloon angioplasty. However, delivery ofthe biologically active material to the body tissue immediately after insertion or implantation ofthe stent may not be needed or desired. For instance, it may be more desirable to wait until restenosis occurs or begins to occur in a body lumen that has been stented with a drug-coated stent before the drug is released. Therefore, there is a need for implantable medical devices that can provide on-demand delivery of biologically active materials when such materials are required by the patient after implantation ofthe medical device. Also needed is a non-invasive method to facilitate or modulate the delivery ofthe biologically active material from the medical device after implantation.

SUMMARY OF THE INVENTION These and other objectives are accomplished by the present invention. To achieve these objectives, we have invented an insertable medical device that permits on- demand delivery of a biologically active material from the medical device when it is implanted in a patient. The release ofthe biologically active material is modulated and/or facilitated by the application of an exfracorporal or external energy source, such as an electromagnetic energy source or a mechanical vibrational energy source. More specifically, the medical device, that is insertable into the body of a patient, comprises a surface and a first coating layer disposed on at least a portion ofthe surface. The first coating layer comprises a biologically active material. A second coating layer is disposed over the first coating layer and comprises magnetic particles and a polymeric material. The second coating layer is substantially free ofthe biologically active material, and preferably free of any biologically active material. When the patient is exposed to an exfracorporal electromagnetic energy source, the release ofthe biologically active material from the coated medical device is facilitated. In this way, the biologically active material can be delivered to the patient only when he or she requires such material.

In order to further achieve the aforementioned objectives, also described herein is a system for providing on-demand delivery of a biologically active material to a patient. This system comprises an insertable medical device that comprises a surface and a first coating layer disposed on at least a portion ofthe surface. The first coating layer comprises a biologically active material. A second coating layer is disposed over the first coating layer and comprises magnetic particles and a polymeric material. The second coating layer is substantially free ofthe biologically active material, and preferably free of any biologically active material. The system also comprises an electromagnetic energy source or mechanical vibrational energy source for facilitating the delivery ofthe biologically active material when the patient is exposed to this energy source.

Another embodiment ofthe invention is a method for a making a medical device for delivering a biologically active material to a patient. The method comprises providing a medical device that is insertable into the body ofthe patient and comprises a surface. The method further comprises disposing a first coating layer comprising a biologically active material on at least a portion ofthe surface ofthe medical device. A second coating layer comprising a polymeric material and magnetic particles is disposed on the first coating layer. The second coating layer is substantially free ofthe biologically active material, and preferably free of any biologically active material. The present medical device of the present invention can provide a desired release profile of a biologically active material. The desired release profile can be achieved because the medical device is coated with a first coating layer comprising a biologically active material and a second coating layer comprising magnetic particles that overlies or covers the first coating layer. The second coating layer is substantially free of a biologically active material so that the biologically active material is not exposed and is protected during implantation and prior to release into the body lumen of a patient. Because the second coating layer is substantially free of any biologically active material, there can be a higher concentration of magnetic particles in the second coating layer than if there were a biologically active material in the second coating layer. In addition, when the magnetic particles in the second coating layer are exposed to an energy source and move out ofthe second layer, the biologically active material is not immediately released. Instead, there is a controlled release ofthe biologically active material because the biologically active material migrates from the first coating layer and through the second coating layer before being delivered to a body lumen of a patient.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE 1 is a cross-sectional view of a stent 10 comprising wire-like struts 20. FIGURE 2A is a cross-sectional view of a coated strut 20 of a stent as shown in FIGURE

1. The coated strut comprises a strut 25 and a surface 30 covered with a coating.

FIGURE 2B shows the effect oh the coated strut of Figure 2A when the patient is exposed to an electromagnetic field 90.

FIGURE 3A is a cross-sectional view of a portion of a coated strut 20 of a stent. FIGURE 3B shows the effect on the strut of Figure 3 A when the patient is exposed to an electromagnetic field 90.

FIGURE 4 A is a cross-sectional view of a coated strut 20 of a stent. FIGURE 4B shows the effect on the strut of Figure 4A when the patient is exposed to an electromagnetic field 90.

FIGURE 5 is a cross-sectional view of a coated strut 20. FIGURE 6 shows an experimental set-up for determining the effect of exposure to an electromagnetic field on a medical device coated with a coating containing a biologically active material.

FIGURE 7 is a graph showing the effect of exposing a coated medical device to an electromagnetic field. FIGURE 8 is a graph showing the effect of exposing a coated medial device to an electromagnetic field when the concentration of magnetic particles in the . coating is varied. FIGURE 9 shows an experimental set-up for determining the effect of exposing a coated medical device to mechanical vibrational energy generated by a stack actuator. FIGURE 10 is a graph showing the effect of exposmg a coated medical device xo mechanical vibration energy.

DETAILED DESCRIPTION OF THE INVENTION A. Drug Release Modulation Employing an Electromagnetic Energy Source

The system ofthe present invention comprises (1) a medical device having a coating containing a biologically active material, and (2) a source of electromagnetic energy or a source for generating an electromagnetic field. The present invention can facilitate and or modulate the delivery ofthe biologically active material from the medical device. The release ofthe biologically active material from the medical device is facilitated or modulated by the electromagnetic energy source or field. To utilize the system ofthe present invention, the practitioner may implant the coated medical device using regular procedures. After implantation, the patient is exposed to an exfracorporal or external electromagnetic energy source or field to facilitate the release ofthe biologically active material from the medical device. The delivery ofthe biologically active material is on- demand, i.e., the material is not delivered or released from the medical device until a practitioner determines that the patient is in need ofthe biologically active material. The coating ofthe medical device ofthe present invention further comprises particles comprising a magnetic material, i.e., magnetic particles. An example ofthe medical device ofthe present invention is illustrated in Figure 1. The medical device is a stent 10 which is comprised of wire-like coated struts 20.

An embodiment ofthe medical device ofthe present invention is illustrated in Figure 2A. Figure 2A shows a cross-sectional view of a coated strut of a stent. The coated strut 20 comprises a strut 25 having a surface 30. The coated strut 20 has a coating that comprises a first coating layer 40 that contains a biologically active material 45.

Preferably, this coating layer also contains a polymeric material. A second coating layer 50 comprising magnetic particles 55 is disposed over the first coating layer 40. This second coating layer can also include a polymeric material. A third coating layer or sealing layer 60 is disposed on top ofthe second coating layer 50. Figure 2B illustrates the effect of exposing a patient, who is implanted with a stent having struts shown in Figure 2 A, to an electromagnetic energy source or field 90. When such a field is applied, the magnetic particles 55 move out ofthe second coating layer 50 as shown by the upward arrow 110. This movement disrupts the sealing layer 60 and forms channels 100 in the sealing layer 60. The size ofthe channels 100 formed generally depends on the size ofthe magnetic particles 55 used. The biologically active material 45 can then be released from the coating through the disrupted sealing layer 60 into the surrounding tissue 120. The duration oi exposure to the field and the strength ofthe electromagnetic field 90 determine the rate of delivery of the biologically active material 45.

Figure 3 A shows another specific embodiment of a coated stent strut 20. The coating comprises a first coating layer 40 comprising a biologically active material 45 and preferably a polymeric material disposed over the surface 30 ofthe strut 25. A second coating layer or sealing layer 70 comprising magnetic particles 55 and a polymeric material is disposed on top ofthe first coating layer 40. Figure 3B illustrates the effect of exposing a patient who is implanted with a stent having struts shown in Figure 3 A, to an electromagnetic field 90. When such a field is applied, the magnetic particles 55 move through the sealing layer 70 as shown by the upward arrow 110 and created channels 100 in the sealing layer 70. The biologically active material 45 in the underlying first coating layer 40 is allowed to travel through the channels 100 in the sealing layer 70 and be released to the surrounding tissue 120. Since the biologically active material 45 is in a separate first coating layer 40 and must migrate through the second coating layer or the sealing layer 70, the release ofthe biologically active material 45 is controlled after formation ofthe channels 100.

Figures 4A shows another embodiment of a coated stent strut. The coating comprises a coating layer 80 comprising a biologically active material 45, magnetic particles 55 and a polymeric material. Figure 4B illustrates the effect of exposing a patient, who is implanted with a stent having struts shown in Figure 4A to an electromagnetic field 90. The field is applied, the magnetic particles 55 move through the layer 80 as shown by the arrow 110 and create channels in the coating layer 80. The biologically active material 45 can then be released to the surrounding tissue 120. In another embodiment, the medical device ofthe present invention may be a stent having struts coated with a coating comprising more than one coating layer containing a magnetic material. Figure 5 illustrates such a coated strut 20. The coating comprises a first coating layer 40 containing a polymeric material and a biologically active material 45 which is disposed on the surface 30 of a strut 25. A second coating layer 50 comprising a polymeric material and magnetic particles 55 is disposed over the first coating layer 40. A third coating layer 44 comprising a polymeric material and a biologically active material 45 is disposed over the second coating layer 50. A fourth coating layer 54 comprising a polymeric material and magnetic particles 55 is disposed over this third layer 44. Finally a sealing layer 60 of a polymeric material is disposed over the fourth coating layer 54. The permeability ofthe coating layers may be different from layer to layer so that the release of the biologically active material from each layer can differ. Also, the magnetic susceptibility ofthe magnetic particles may differ from layer to layer. The magnetic susceptibility may be varied using different concentrations or percentages of magnetic particles in the coating layers. The magnetic susceptibility ofthe magnetic particles may also be varied by changing the size and type of material used for the magnetic particles. When the magnetic susceptibility ofthe magnetic particles differs from layer to layer, different excitation intensity and/or frequency are required to activate the magnetic particles in each layer.

Furthermore, the magnetic particles can be coated with a biologically active material and then incorporated into a coating for the medical device. In a preferred embodiment, the biologically active material is a nucleic acid molecule. The nucleic acid coated magnetic particles may be formed by painting, dipping, or spraying the magnetic particles with a solution comprising the nucleic acid. The nucleic acid molecules may adhere to the magnetic particles via adsorption. Also the nucleic acid molecules may be linked to the magnetic particles chemically, via linking agents, covalent bonds, or chemical groups that have affinity for charged molecules. Application of an external electromagnetic field can cause the adhesion between the biologically active material and the magnetic particle to break, thereby allowing for release ofthe biologically active material.

In another specific embodiment, the magnetic particles may be molded into or coated onto a non-metallic medical device, including a bio-absorbable medical device. The magnetic properties ofthe magnetic particles allow the non-metallic implant to be extracorporally imaged, vibrated, or moved. In specific embodiments, the magnetic particles are painted, dipped or sprayed onto the outer surface ofthe device. The magnetic particles may also be suspended in a curable coating, such as a UN curable epoxy, or they may be electrostatically sprayed onto the medical device and subsequently coated with a UN or heat curable polymeric material.

Furthermore, in certain embodiments, the movement ofthe magnetic particles that occurs when the patient implanted with the coated device is exposed to an external electromagnetic field, can release mechanical energy into the surrounding tissue in which the medical device is implanted and trigger histamine production by the surrounding tissues. The histamine has a protective effect in preventing the formation of scar tissues in the vicinity at which the medical device is implanted.

Also the application ofthe external electromagnetic field can activate the biologically active material in the coating ofthe medical device. A biologically active material that may be used in this embodiment may be a thermally sensitive substance that is coupled to nitric oxide, e.g., nitric oxide adducts, which prevent and/or freat adverse effects associated with use of a medical device in a patient, such as restenosis and damaged blood vessel surface. The nitric oxide is attached to a carrier molecule and suspended in the polymer ofthe coating, but it is only biologically active after a bond breaks releasing the smaller nitric oxide molecule in the polymer and eluting into the surrounding tissue. Typical nitric oxide adducts include nitroglycerin, sodium nitroprusside, S-nifroso-proteins, S- nitroso-thiols, long carbon-chain lipophilic S-nitrosothiols, S-nifrosodithiols, iron-nitrosyl compounds, thionitrates, thionitrites, sydnonimines, furoxans, organic nitrates, and nitrosated amino acids, preferably mono- or poly-nitrosylated proteins, particularly polynitrosated albumin or polymers or aggregates thereof. The albumin is preferably human or bovine, including humamzed bovine serum albumin. Such nitric oxide adducts are disclosed in U.S. Patent No. 6,087,479 to Stamler et al. which is incorporated herein by reference.

Moreover, the application of electromagnetic field may effect a chemical change in the polymer coating thereby allowing for faster release ofthe biologically active material from the coating.

B. Drug Release Modulation Employing a Mechanical Vibrational Energy Source

Another embodiment ofthe present invention is a system for delivering a biologically active material to a body of a patient that comprises a mechanical vibrational energy source and an insertable medical device comprising a coating containing the biologically active material. The coating can optionally contain magnetic particles. After the device is implanted in a patient, the biologically active material can be delivered to the patient on-demand or when the material is needed by the patient. To deliver the biologically active material, the patient is exposed to an exfracorporal or external mechanical vibrational energy source. The mechanical vibrational energy source includes various sources which cause vibration such as sonic or ultrasonic energy. Exposure to such energy source causes disruption in the coating that allows for the biologically active material to be released from the coating and delivered to body tissue.

Moreover, in certain embodiments, the biologically active material contained in the coating ofthe medical device is in a modified form. The modified biologically active material has a chemical moiety bound to the biologically active material. The chemical bond between the moiety and the biologically active material is broken by the mechanical vibrational energy. Since the biologically active material is generally smaller than the modified biologically active material, it is more easily released from the coating. Examples of such modified biologically active materials include the nitric oxide adducts described above.

In another embodiment, the coating comprises at least a coating layer containing a polymeric material whose structural properties are changed by mechanical vibrational energy. Such change facilitates release ofthe biologically active material which is contained in the same coating layer or another coating layer.

C. Materials Suitable for the Invention 1. Suitable Medical Devices The medical devices ofthe present invention are insertable into the body of a patient. Namely, at least a portion of such medical devices may be temporarily inserted into or semi-permanently or permanently implanted in the body of a patient. Preferably, the medical devices ofthe present invention comprise a tubular portion which is insertable into the body of a patient. The tubular portion ofthe medical device need not to be completely cylindrical. For instance, the cross-section ofthe tubular portion can be any shape, such as rectangle, a triangle, etc., not just a circle.

The medical devices suitable for the present invention include, but are not limited to, stents, surgical staples, catheters, such as central venous catheters and arterial catheters, guidewires, balloons, filters (e.g., vena cava filters), cannulas, cardiac pacemaker leads or lead tips, cardiac defibrillator leads or lead tips, implantable vascular access ports, stent grafts, vascular grafts or other grafts, interluminal paving system, infra-aortic balloon pumps, heart valves, cardiovascular sutures, total artificial hearts and ventricular assist pumps.

Medical devices which are particularly suitable for the present invention include any kind of stent for medical purposes, which are known to the skilled artisan. Suitable stents include, for example, vascular stents such as self-expanding stents and balloon expandable stents. Examples of self-expanding stents useful in the present invention are illustrated in U.S. Patent Nos. 4,655,771 and 4,954,126 issued to Wallsten and 5,061,275 issued to Wallsten et al. Examples of appropriate balloon-expandable stents are shown in U.S. Patent No. 4,733,665 issued to Palmaz, U.S. Patent No. 4,800,882 issued to Gianturco, U.S. Patent No. 4,886,062 issued to Wiktor and U.S. Patent No. 5,449,373 issued to Pinchasik et al. A bifurcated stent is also included among the medical devices suitable for the present invention.

The medical devices suitable for the present invention may be fabricated from polymeric and/or metallic materials. Examples of such polymeric materials include polyurethane and its copolymers, silicone and its copolymers, ethylene vmyl-acetate, poly(ethylene terephthalate), thermoplastic elastomer, polyvinyl chloride, polyolephines, cellulosics, polyamides, polyesters, polysulfones, polytefrafluoroethylenes, acrylonitrile butadiene styrene copolymers, acrylics, polyactic acid, polyclycolic acid, polycaprolactone, polyacetal, poly(lactic acid), polylactic acid-polyethylene oxide copolymers, polycarbonate cellulose, collagen and chitins. Examples of suitable metallic materials include metals and alloys based on titanium (e.g., nitinol, nickel titanium alloys, thermo-memory alloy materials), stainless steel, platinum, tantalum, nickel-chrome, certain cobalt alloys including cobalt-chromium-nickel alloys (e.g., Elgiloy® and Phynox®) and gold/platinum alloy. Metallic materials also include clad composite filaments, such as those disclosed in WO 94/16646.

2. Magnetic Particles

In the instant specification, the term "magnetic particles" means particles comprising a magnetic material. Magnetic materials include ferromagnetic substances, i.e., substances which exhibit good magnetic susceptibility, such as ferrous substance including iron oxide steel, stainless steel; paramagnetic substances, such as aluminum, which have unpaired electrons and are attracted into a magnetic field; diamagnetic substances, such as gold, wherein all electrons are paired and are slightly repelled by the electromagnetic field. Preferably, the magnetic particles used for the present invention comprise a ferromagnetic substance. However, magnetic particles comprising paramagnetic or diamagnetic substances are particularly useful for imaging the medical device in a patient's body, for example, using magnetic resonance imaging ("MRI") because the strong magnetic field in MRI would not negatively affect the particles but would enable or enhance the ability of MRI to detect them. The magnetic particles may be capsules made of non-magnetic substance, such as silica, encapsulating a magnetic substance or particles made of a mixture of a nonmagnetic substance and a magnetic substance. Also, the magnetic particles may be coated with a polymeric material to reduce any undesirable effects that may be caused by the corrosive nature ofthe magnetic substance. In another embodiment, ferrous loaded polymers are incorporated into the coating instead of magnetic particles. Examples ofthe ferrous loaded polymers include iron dextran.

The average size ofthe particles is normally within the range from about 0.01 μm to about 10 μm. However, the average particle size may be any other suitable range such as from about 0.01 μm to about 50 μm. The sizes should be determined based on various factors including a thickness ofthe coating layer in which the particles are contained or by which the particles are covered, and desired release rate ofthe biologically active material. Also, when the biologically active material to be released from the medical device has comparatively greater size, i.e., cells or other large size genetic materials, the magnetic particles of greater size should be chosen. Suitable particles are not limited to any particular shape.

Magnetic particles useful for the present invention, such as magnetic iron oxide particles (mean particle diameter 200 nm, density 5.35 g/cm³ and magnetization 30 emu/g) and magnetic silica particles, Sicaster-M™ (mean particle diameter 800-1500 nm, density 2.5 g/cm³ and magnetization -4.0 emu/g) are commercially available, for example, from Micromod Partikeltechnologie.

The concentration ofthe magnetic particles in a coating should be determined based on various factors including the size ofthe particles and desired release rate ofthe biologically active material. Normally, the concentration ofthe magnetic particles in a coating ranges from about 2% to about 20 %. 3. Biologically Active Material

The term "biologically active material" encompasses therapeutic agents, such as drugs, and also genetic materials and biological materials. The genetic materials mean DNA or RNA, including, without limitation, of DNA/RNA encoding a useful protein stated below, anti-sense DNA/RNA, intended to be inserted into a human body including viral vectors and non- viral vectors. Examples of DNA suitable for the present invention include DNA encoding anti-sense RNA tRNA or rRNA to replace defective or deficient endogenous molecules angiogenic factors including growth factors, such as acidic and basic fibroblast growth factors, vascular endothelial growth factor, epidermal growth factor, transforming growth factor and β, platelet-derived endothelial growth factor, platelet- derived growth factor, tumor necrosis factor a, hepatocyte growth factor and insulin like growth factor cell cycle inhibitors including CD inhibitors - thymidine kinase ("TK") and other agents useful for interfering with cell proliferation, and the family of bone morphogenic proteins ("BMP's") as explained below. Viral vectors include adenoviruses, gutted adenoviruses, adeno-associated virus, retroviruses, alpha virus (Semliki Forest, Sindbis, etc.), lentiviruses, herpes simplex virus, ex vivo modified cells (e.g., stem cells, fibroblasts, myoblasts, satellite cells, pericytes, cardiomyocytes, sketetal myocytes, macrophage), replication competent viruses (e.g., ONYX-015), and hybrid vectors. Non-viral vectors include artificial chromosomes and mini-chromosomes, plasmid DNA vectors (e.g., pCOR), cationic polymers (e.g., polyethyleneimine, polyethyleneimine (PEI)) graft copolymers (e.g., polyether-PEI and polyethylene oxide-PEI), neutral polymers PVP, SP1017 (SUPRATEK), lipids or lipoplexes, nanoparticles and microparticles with and without targeting sequences such as the protein fransduction domain (PTD).

The biological materials include cells, yeasts, bacteria, proteins, peptides, cytokines and hormones. Examples for peptides and proteins include growth factors (FGF, FGF-1, FGF-2, VEGF, Endotherial Mitogenic Growth Factors, and epidermal growth factors, transforming growth factor and β, platelet derived endothelial growth factor, platelet derived growth factor, tumor necrosis factor a, hepatocyte growth factor and insulin like growth factor), transcription factors, proteinkinases, CD inhibitors, thymidine kinase, and bone morphogenic proteins (BMP's), such as BMP-2, BMP-3, BMP-4, BMP-5, BMP-6 (Vgr-1), BMP-7 (OP-1), BMP-8. BMP-9, BMP-10, BMP-11, BMP-12, BMP-13, BMP-14, BMP-15, and BMP-16. Currently preferred BMP's are BMP-2, BMP-3, BMP-4, BMP-5, BMP-6, BMP-7. Alternatively or in addition, molecules capable of inducing an upsfream or downstream effect of a BMP can be provided. Such molecules include any ofthe "hedgehog" proteins, or the DNA's encoding them. These dimeric proteins can be provided as homodimers, heterodimers, or combinations thereof, alone or together with other molecules. Cells can be of human origin (autologous or allogeneic) or from an animal source (xenogeneic), genetically engineered, if desired, to deliver proteins of interest at the transplant site. The delivery media can be formulated as needed to maintain cell function and viability. Cells include whole bone marrow, bone marrow derived mono-nuclear cells, progenitor cells (e.g., endothelial progentitor cells) stem cells (e.g., mesenchymal, hematopoietic, neuronal), pluripotent stem cells, fibroblasts, macrophage, and satellite cells.

Biologically active material also includes non-genetic therapeutic agents, such as: • anti-thrombogenic agents such as heparin, heparin derivatives, urokinase, and PPack

(dextrophenylalanine proline arginine chloromethylketone);

• anti-proliferative agents such as enoxaprin, angiopeptin, or monoclonal antibodies capable of blocking smooth muscle cell proliferation, hirudin, and acetylsalicylic acid, amlodipine and doxazosin; anti-inflammatory agents such as glucocorticoids, betamethasone, dexametnasone, prednisolone, corticosterone, budesonide, estrogen, sulfasalazine, and mesalamine;

• immunosuppressants such as sirolimus (RAPAMYCIN), tacrolimus, everolimus and dexamethasone, • antineoplastic/antiproliferative/anti-miotic agents such as paclitaxel, 5-fluorouracil, cisplatin, vinblastine, vincristine, epothilones, methotrexate, azathioprine, halofuginone, adriamycin, actinomycin and mutamycin; cladribine; endostatin, angiostatin and thymidine kinase inhibitors, and its analogs or derivatives;

• anesthetic agents such as lidocaine, bupivacaine, and ropivacaine; • anti-coagulants such as D-Phe-Pro-Arg chloromethyl keton, an RGD peptide-containing compound, heparin, antithrombin compounds, platelet receptor antagonists, anti-thrombin antibodies, anti-platelet receptor antibodies, aspirin (aspirin is also classified as an analgesic, antipyretic and anti-inflammatory drug), dipyridamole, protamine, hirudin, prostaglandin inhibitors, platelet inhibitors and tick antiplatelet peptides;

• vascular cell growth promotors such as growth factors, Vascular Endothelial Growth Factors (FEGF, all types including NEGF-2), growth factor receptors, transcriptional activators, and translational promotors;

• vascular cell growth inhibitors such as antiproliferative agents, growth factor inhibitors, growth factor receptor antagonists, transcriptional repressors, translational repressors, replication inhibitors, inhibitory antibodies, antibodies directed against growth factors, bifunctional molecules consisting of a growth factor and a cytotoxin, bifunctional molecules consisting of an antibody and a cytotoxin;

• cholesterol-lowering agents; vasodilating agents; and agents which interfere with endogenous vasoactive mechanisms;

• anti-oxidants, such as probucol;

• antibiotic agents, such as penicillin, cefoxitin, oxacillin, tobranycin

• angiogenic substances, such as acidic and basic fibrobrast growth factors, estrogen including estradiol (E2), estriol (E3) and 17-Beta Esfradiol; and • drugs for heart failure, such as digoxin, beta-blockers, angiotensin-converting enzyme (ACE) inhibitors including captopril and enalopril.

Also, the biologically active materials ofthe present invention include trans- retinoic acid and nitric oxide adducts. A biologically active material may be encapsulated in micro-capsules by the known methods. 4. Coating Compositions

The coating compositions suitable for the present invention can be applied by any method to a surface of a medical device to form a coating. Examples of such methods are painting, spraying, dipping, rolling, electrostatic deposition and all modern chemical ways of immobilization of bio-molecules to surfaces.

The coating composition used in the present invention may be a solution or a suspension of a polymeric material and/or a biologically active material and/or magnetic particles in an aqueous or organic solvent suitable for the medical device which is known to the skilled artisan. A slurry, wherein the solid portion ofthe suspension is comparatively large, can also be used as a coating composition for the present invention. Such coating composition may be applied to a surface, and the solvent may be evaporated, and optionally heat or ultraviolet (UN) cured.

The solvents used to prepare coating compositions include ones which can dissolve the polymeric material into solution and do not alter or adversely impact the therapeutic properties ofthe biologically active material employed. For example, useful solvents for silicone include tetrahydrofuran (THF), chloroform, toluene, acetone, isooctane, 1,1,1-trichloroethane, dichloromethane, and mixture thereof .

A coating of a medical device ofthe present invention may consist of various combinations of coating layers. For example, the first layer disposed over the surface ofthe medical device can contain a polymeric material and a first biologically active material. The second coating layer, that is disposed over the first coating layer, contains magnetic particles and optionally a polymeric material. The second coating layer protects the biologically active material in the first coating layer from exposure during implantation and prior to delivery. Preferably, the second coating layer is substantially free of a biologically active material.

Another layer, i.e. sealing layer, which is free of magnetic particles, can be provided over the second coating layer. Further, there may be another coating layer containing a second biologically active material disposed over the second coating layer. The first and second biologically active materials may be identical or different. When the first and second biologically active material are identical, the concenfration in each layer may be different. The layer containing the second biologically active material may be covered with yet another coating layer containing magnetic particles. The magnetic particles in two different layers may have an identical or a different average particle size and/or an identical or a different concentrations. The average particle size and concentration can be varied to obtain a desired release profile ofthe biologically active material, hi addition, the skilled artisan can choose other combinations of those coatmg layers.

Alternatively, the coating of a medical device ofthe present invention may comprise a layer containing both a biologically active material and magnetic particles. For example, the first coating layer may contain the biologically active material and magnetic particles, and the second coating layer may contain magnetic particles and be substantially free of a biologically active material, hi such embodiment, the average particle size ofthe magnetic particles in the first coating layer may be different than the average particle size of the magnetic particles in the second coating layer. In addition, the concentration ofthe magnetic particles in the first coating layer may be different than the concentration ofthe magnetic particles in the second coating layer. Also, the magnetic susceptibility ofthe magnetic particles in the first coating layer may be different than the magnetic susceptibility ofthe magnetic particles in the second coating layer.

The polymeric material should be a material that is biocompatible and avoids irritation to body tissue. Examples of the polymeric materials used in the coating composition ofthe present invention include, but not limited to, polycarboxylic acids, cellulosic polymers, including cellulose acetate and cellulose nitrate, gelatin, polyvinylpyrrolidone, cross-linked polyvinylpyrrolidone, polyanhydrides including maleic anhydride polymers, polyamides, polyvinyl alcohols, copolymers of vinyl monomers such as EVA, polyvinyl ethers, polyvinyl aromatics, polyethylene oxides, glycosammoglycans, polysaccharides, polyesters including polyethylene terephthalate, pofyacrylamides, polyethers, polyether sulfone, polycarbonate, polyalkylenes including polypropylene, polyethylene and high molecular weight polyethylene, halogenated polyalkylenes including polytefrafluoroethylene, polyurethanes, polyorthoesters, proteins, polypeptides, silicones, siloxane polymers, polylactic acid, polyglycolic acid, polycaprolactone, polyhydroxybutyrate valerate, styrene-isobutylene copolymers and blends and copolymers thereof. Also, other examples of such polymers include polyurethane (BAYHDROL®, etc.) fibrin, collagen and derivatives thereof, polysaccharides such as celluloses, starches, dextrans, alginates and derivatives, hyaluronic acid, and squalene. Further examples ofthe polymeric materials used in the coating composition ofthe present invention include other polymers which can be used include ones that can be dissolved and cured or polymerized on the medical device or polymers having relatively low melting points that can be blended with biologically active materials. Additional suitable polymers include, thermoplastic elastomers in general, polyolefins, polyisobutylene, ethylene-alphaolefin copolymers, acrylic polymers and copolymers, vinyl halide polymers and copolymers such as polyvinyl chloride, polyvinyl ethers such as polyvinyl methyl ether, polyvinyhdene halides such as polyvinylidene fluoride and polyvinyhdene chloride, polyacrylonitrile, polyvinyl ketones, polyvinyl aromatics such as polystyrene, polyvinyl esters such as polyvinyl acetate, copolymers of vinyl monomers, copolymers of vinyl monomers and olefins such as ethylene-methyl methacrylate copolymers, acrylonitrile-styrene copolymers, ABS

(acrylonitrile-butadiene-styrene) resins, ethylene-vinyl acetate copolymers, polyamides such as Nylon 66 and polycaprolactone, alkyd resins, polycarbonates, polyoxymethylenes, polyimides, epoxy resins, rayon-triacetate, cellulose, cellulose acetate, cellulose butyrate, cellulose acetate butyrate, cellophane, cellulose nitrate, cellulose propionate, cellulose ethers, carboxymethyl cellulose, collagens, chitins, polylactic acid, polyglycolic acid, polylactic acid-polyethylene oxide copolymers, EPDM (etylene-propylene-diene) rubbers, fluorosilicones, polyethylene glycol, polysaccharides, phospholipids, and combinations of the foregoing. Preferred is polyacrylic acid, available as HYDROPLUS® (Boston Scientific Corporation, Natick, Mass.), and described in U.S. Pat. No. 5,091,205, the disclosure of which is hereby incorporated herein by reference. In a most preferred embodiment ofthe invention, the polymer is a copolymer of polylactic acid and polycaprolactone.

More preferably for medical devices which undergo mechanical challenges, e.g. expansion and contraction, the polymeric materials should be selected from elastomeric polymers such as silicones (e.g. polysiloxanes and substituted polysiloxanes), polyurethanes, thermoplastic elastomers, ethylene vinyl acetate copolymers, polyolefin elastomers, and EPDM rubbers. Because ofthe elastic nature of these polymers, the coating composition adheres better to the surface ofthe medical device when the device is subjected to forces, stress or mechanical challenge. The amount ofthe polymeric material present in the coatings can vary based on the application for the medical device. One skilled in the art is aware of how to determine the desired amount and type of polymeric material used in the coating. For example, the polymeric material in the first coating layer may be the same as or different than the polymeric material in the second coating layer. The thickness ofthe coating is not limited, but generally ranges from about 25 μm to about 0.5 mm. Preferably, the thickness is about 30 μm to 100 μm.

5. Electromagnetic Sources

An external electromagnetic source or field may be applied to the patient having an implanted coated medical device using any method known to skilled artisan, hi the method ofthe present invention, the electromagnetic field is oscillated. Examples of devices which can be used for applying an electromagnetic field include a magnetic resonance imaging ("MRI") apparatus. Generally, the magnetic field strength suitable is within the range of about 0.50 to about 5 Tesla (Webber per square meter). The duration of the application may be determined based on various factors including the strength ofthe magnetic field, the magnetic substance contained in the magnetic particles, the size ofthe particles, the material and thickness ofthe coating, the location ofthe particles within the coating, and desired releasing rate ofthe biologically active material.

In an MRI system, an electromagnetic field is uniformly applied to an object under inspection. At the same time, a gradient magnetic field, superposing the electromagnetic field, is applied to the same. With the application of these elecfromagnetic fields, the object is applied with a selective excitation pulse of an elecfromagnetic wave with a resonance frequency which corresponds to the electromagnetic field of a specific atomic nucleus. As a result, a magnetic resonance (MR) is selectively excited. A signal generated is detected as an MR signal. See U.S. Patent Nos. 4,115,730 to Mansfield, 4,297,637 to Crooks et ah, and 4,845,430 to Nakagayashi. For the present invention, among the functions ofthe MRI apparatus, the function to create an elecfromagnetic field is useful for the present invention. The implanted medical device ofthe present can be located as usually done for MRI imaging, and then an electromagnetic field is created by the MRI apparatus to facilitate release ofthe biologically active material. The duration of the procedure depends on many factors, including the desired releasing rate and the location ofthe inserted medical device. One skilled in the art can determine the proper cycle ofthe electromagnetic field, proper intensity ofthe electromagnetic field, and time to be applied in each specific case based on experiments using an animal as a model. hi addition, one skilled in the art can determine the excitation source frequency ofthe elecromagnetic energy source. For example, the electromagnetic field can have an excitation source frequency in the range of about 1 Hertz to about 300 kiloHertz. Also, the shape ofthe frequency can be of different types. For example, the frequency can be in the form of a square pulse, ramp, sawtooth, sine, triangle, or complex. Also, each form can have a varying duty cycle. 6. Mechanical Vibrational Energy Source

The mechanical vibrational energy source includes various sources which cause vibration such as ultrasound energy. Examples of suitable ultrasound energy are disclosed in U.S. Patents No. 6,001,069 to Tachibana et al. and No. 5,725494 to Brisken, PCT publications WOOO/16704, WO00/18468, WO00/00095, WO00/07508 and WO99/33391, which are all incorporated herein by reference. Strength and duration ofthe mechanical vibrational energy ofthe application may be determined based on various factors including the biologically active material contained in the coating, the thickness of the coating, structure ofthe coating and desired releasing rate ofthe biologically active material. Various methods and devices may be used in connection with the present invention. For example, U.S. Patent No. 5,895,356 discloses a probe for transurethrally applying focused ultrasound energy to produce hyperthermal and thermotherapeutic effect in diseased tissue. U.S. Patent No. 5,873,828 discloses a device having an ultrasonic vibrator with either a microwave or radio frequency probe. U.S. Patent No. 6,056,735 discloses an ultrasonic treating device having a probe connected to a ultrasonic fransducer and a holding means to clamp a tissue. Any of those methods and devices can be adapted for use in the method ofthe present invention.

Ultrasound energy application can be conducted percutaneously through small skin incisions. An ultrasonic vibrator or probe can be inserted into a subject's body through a body lumen, such as blood vessels, bronchus, urethral tract, digestive tract, and vagina. However, an ultrasound probe can be appropriately modified, as known in the art, for subcutaneous application. The probe can be positioned closely to an outer surface ofthe patient body proximal to the inserted medical device.

The duration ofthe procedure depends on many factors, including the desired releasing rate and the location ofthe inserted medical device. The procedure may be performed in a surgical suite where the patient can be monitored by imaging equipment. Also, a plurality of probes can be used simultaneously. One skilled in the art can determine the proper cycle ofthe ultrasound, proper intensity ofthe ultrasound, and time to be applied in each specific case based on experiments using an animal as a model. In addition, one skilled in the art can determine the excitation source frequency ofthe mechanical vibrational energy source. For example, the mechanical vibrational energy source can have an excitation source frequency in the range of about 1 Hertz to about 300 kiloHertz. Also, the shape ofthe frequency can be of different types. For example, the frequency can be in the form of a square pulse, ramp, sawtooth, sine, triangle, or complex. Also, each form can have a varying duty cycle.

D. Treatment of Body Tissue With the Invention

The present invention provides a method of treatment to reduce or prevent the degree of restenosis or hyperplasia after vascular intervention such as angioplasty, stenting, atherectomy and grafting. All forms of vascular intervention are contemplated by the invention, including, those for treating diseases ofthe cardiovascular and renal system. Such vascular intervention include, renal angioplasty, percutaneous coronary intervention (PCI), percutaneous transluminal coronary angioplasty (PTCA); carotid percutaneous transluminal angioplasty (PTA); coronary by-pass grafting, angioplasty with stent implantation, peripheral percutaneous transluminal intervention ofthe iliac, femoral or popliteal arteries, carotid and cranial vessels, surgical intervention using impregnated artificial grafts and the like. Furthermore, the system described in the present invention can be used for treating vessel walls, portal and hepatic veins, esophagus, intestine, ureters, urethra, intracerebrally, lumen, conduits, channels, canals, vessels, cavities, bile ducts, or any other duct or passageway in the human body, either in-born, built in or artificially made. It is understood that the present invention has application for both human and veterinary use.

The present invention also provides a method of treatment of diseases and disorders involving cell overproliferation, cell migration, and enlargement. Diseases and disorders involving cell overproliferation that can be treated or prevented include but are not limited to malignancies, premalignant conditions (e.g., hyperplasia, metaplasia, dysplasia), benign tumors, hyperproliferative disorders, benign dysproliferative disorders, ete. that may or may not result from medical intervention. For a review of such disorders, see Fishman et al., 1985, Medicine, 2d Ed., J.B. Lippincott Co., Philadelphia. Whether a particular treatment ofthe invention is effective to treat restenosis or hyperplasia of a body lumen can be determined by any method known in the art, for example but not limited to, those methods described in this section. The safety and efficiency ofthe proposed method of treatment of a body lumen may be tested in the course of systematic medical and biological assays on animals, toxicological analyses for acute and systemic toxicity, histological studies and functional examinations, and clinical evaluation of patients having a variety of indications for restenosis or hyperplasia in a body lumen.

The efficacy ofthe method ofthe present invention may be tested in appropriate animal models, and in human clinical trials, by any method known in the art. For example, the animal or human subject may be evaluated for any indicator of restenosis or hyperplasia in a body lumen that the method ofthe present invention is intended to treat. The efficacy ofthe method ofthe present invention for treatment of restenosis or hyperplasia can be assessed by measuring the size of a body lumen in the animal model or human subject at suitable time intervals before, during, or after freatment. Any change or absence of change in the size ofthe body lumen can be identified and correlated with the effect ofthe treatment on the subject. The size of the body lumen can be determined by any method known in the art, for example, but not limited to, angiography, ultrasound, fluoroscopy, magnetic resonance imaging, optical coherence tumography and histology.

EXAMPLES Example 1

To determine the effect of an electromagnetic field on a coated stent with a biologically active material, 15mm long Nygene PVC tubes with outer circumferences of 11mm were chosen to model a coronary stent. This model was chosen because it is approximately the size of a coronary stent but has much greater surface area on which to load a biologically active material and minimum magnetic properties. The tubes were coated by a coating composition comprising a biologically active material, polymer and particles of a magnetic material. The biologically active material used in the coating was dexamethasone fluorescein (DMF), which has a molecular weight of 840.98 and is hydrophobic. DMF comprises dexamethasone tagged with a fluoroisothiocyanate (FITC) molecule that has an absorbance wavelength of 490 nm and an excitation wavelength of 520 nm. Iron oxide particles were used as the magnetic material particles. These particles had a mean particle diameter of 200 nm and a density of 5.35 g/cm³. The iron oxide particles also had a magnetization of 30 emu/g.

Since the iron oxide particles, which were obtained from Micromed Partikeltechnologie, are suspended in water, an appropriate amount ofthe suspension was pipetted into a vial and the water was evaporated off at 37 °C. A coating composition composed of 0.3% of DMF, 0.5% of a polymer, 0.2% iron oxide particles and 99% ofthe solvent tefrahydrofuran (THF) was prepared. This composition was sonicated for 5 minutes to disperse the iron oxide particles into the organic solvent. The composition was stable for approximately 2 minutes, which was sufficient for coating the PVC tubes. The PVC tubes were coated by completely immersing them in the coating composition and then agitating them for about 30 seconds. The PVC tubes were then air-dried for a minimum of 20 minutes. This process was repeated to create a second coat. Coated PVC tubes coated with about 350 μg to about 550 μg coating material were obtained. The coated tubes were immersed in 1.5 mL deionized water baths and positioned under electromagnetic field generator coils, as shown in Figure 6. The elecfromagnetic field was pulsed at 150 Hz for 10 sec/minute for 30 minutes. As controls, certain ofthe coated tubes were immersed in deionized water baths without exposure to an electromagnetic field. Immediately after exposure to the electromagnetic field, samples of the water from the baths containing the coated tubes exposed to the electromagnetic field and the controls were aliquoted into a plate-reader and analyzed by the SPECTRAmax® Microplate Spectrofluorometer to determine the amount of DMF released into the baths. The amount of DMF released is measured in terms of Random fluorescence unit (RFU) per μL/mg DMF. Figure 7 shows RFU/μL/mg, normalized for the quantity of water sampled for fluorescence and coating weight variations, with standard deviation bars for three (3) measurements of DMF released from the coated tubes under an electromagnetic field. This figure shows that application ofthe electromagnetic field to the coated tubes increases the release ofthe DMF as compared to the controls. Example 2 To determine the minimum magnetic property that the coating needs to have for release rate facilitation to occur release under an elecfromagnetic field, the procedure of Example 1 was repeated. However, the concentrations of magnetic particles in the coating was varied to find a threshold level of magnetic property that a coating should have to facilitate DMF release from the coating under an electromagnetic field. Each coating composition contained 0.5% of a polymer and 99% ofthe solvent tefrahydrofuran (THF), and the percentages ofthe iron oxide particles and DMF were varied; the percentage ofthe iron oxide particles were reduced to 20 %, 10 % and 2 %, while the percentage of DMF was increased accordingly.

The amount of DMF released is measured in terms of Random fluorescence unit (RFU) per μL/mg DMF by an identical manner as in Example 1. Figure 8 shows

RFU/μL/mg values for different concentrations ofthe magnetic particles. This figure shows that the coating containing from 2 % to 20% of iron oxide particles facilitate the release of DMF under the electromagnetic field. Example 3 To determine the effect of mechanical vibrational energy on a coronary stent coated with a biologically active material, 15mm long Nygene PVC tubes with outer circumferences of 11mm were chosen to model a coronary stent. A coating composition composed of 0.3% of DMF, 0.7% of a polymer and 99% of THF was prepared. The PVC tubes were dip-coated in the coating composition. The coated tubes were coupled to a stack actuator with a UV cured epoxy at one of their ends.

The coupled tubes were immersed in 1.5 mL deionized water baths, as shown in Figure 9. The stack actuator was supplied with a sinusoidal signal at approximately 74.5kHz for 30 minutes at 20N. The input frequency was selected based on results showing that the natural frequency of a coronary stent is about 74.5kHz. As controls, certain ofthe coated tubes were immersed in deionized water baths without being coupled with stack actuator. Samples ofthe water from the baths containing the tubes exposed to the mechanical vibrational energy and the controls were analyzed with a spectrofluorimeter to determine the amount of DMF released into the baths. The results were scaled to account for volume of water tested and actual amount of DMF in the coating ofthe tubes (to account for variation in coating weight). The results were shown in Figure 10. This figure shows that application ofthe mechanical vibrational energy to the coated tubes increased the release ofthe DMF as compared to the controls.

The description contained herein is for purposes of illustration and not for purposes of limitation. Changes and modifications may be made to the embodiments ofthe description and still be within the scope ofthe invention. Furthermore, obvious changes, modifications or variations will occur to those skilled in the art. Also, all references cited above are incorporated herein, in their entirety, for all purposes related to this disclosure.

Claims

THE CLAIMS

We claim:

I . A medical device that is insertable into the body of a patient comprising: (a) a surface; (b) a first coating layer comprising a biologically active material disposed on at least a portion ofthe surface; and

(c) a second coating layer comprising a polymeric material and magnetic particles disposed on the first coating layer, wherein the second coating layer is substantially free ofthe biologically active material.

2. The medical device of claim 1, wherein the first coating layer is substantially free ofthe magnetic particles.

3. The medical device of claim 1 , wherein the first coating layer further comprises a polymeric material.

4. The medical device of claim 3, wherein the polymeric material in the first coating layer is different than the polymeric material in the second coating layer.

5. The medical device of claim 1 , wherein the magnetic particles have an average particle size of about 0.01 μm to about 50 μm.

6. The medical device of claim 5, wherein the magnetic particles have an average particle size of about 0.01 μm to about 10 μm.

7. The medical device of claim 1, wherein the magnetic particles comprise a paramagnetic substance or a ferromagnetic substance.

8. The medical device of claim 1 , wherein the magnetic particles are iron oxide particles or magnetic silica particles.

9. The medical device of claim 1 , wherein the first coating layer further comprises magnetic particles.

10. The medical device of claim 9, wherein the average particle size ofthe magnetic particles in the first coating layer is different than the average particle size ofthe magnetic particles in the second coating layer.

I I . The medical device of claim 9, wherein the concentration of the magnetic particles in the first coating layer is different than the concenfration ofthe magnetic particles in the second coating layer.

12. The medical device of claim 9, wherein the magnetic susceptibility of the magnetic particles in the first coating layer is different than the magnetic susceptibility of the magnetic particles in the second coating layer.

13. The medical device of claim 1, further comprising a sealing layer disposed on the second coating layer, wherein the sealing layer comprises a polymeric material and is substantially free ofthe biologically active material and the magnetic particles.

14. The medical device of claim 1, wherein the medical device is a stent having a sidewall comprising a plurality of struts, and wherein the surface is a part ofthe struts.

15. A system for delivering a biologically active material to a patient comprising:

(a) a medical device that is insertable into the body of the patient which comprises a surface; a first coating layer comprising a biologically active material disposed on at least a portion ofthe surface; and a second coating layer comprising a polymeric material and magnetic particles disposed on the first coating layer, wherein the second coating layer is substantially free of the biologically active material; and

(b) an electromagnetic energy source or a mechanical vibrational energy source for facilitating the delivery ofthe biologically active material.

16. The system of claim 15, wherein the first coating layer further comprises a polymeric material.

17. The system of claim 15, wherein the first coating layer is substantially free ofthe magnetic particles.

18. The system of claim 15, further comprising a sealing layer comprising a polymeric material disposed on the second coating layer, wherein the sealing layer is substantially free ofthe magnetic particles.

19. The system of claim 15, wherein the medical device is a stent having a sidewall comprising a plurality of struts, and wherein the surface is a part ofthe struts.

20. The system of claim 15, wherein the electromagnetic energy source or the mechanical vibrational energy source has an excitation source frequency in the range of about 1 Hz to about 300 kHz

21. The system of claim 15, wherein the electromagnetic energy source is a magnetic resonance imaging apparatus.

22. The system of claim 15, wherein the mechamcal vibrational energy source is a sonic energy source or an ultrasonic energy source.

23. The system of claim 15, wherein the magnetic particles have an average particle size of about 0.01 μm to about 50 μm.

24. The system of claim 23, wherein the magnetic particles have an average particle size of about 0.01 μm to about 10 μm.

25. The system of claim 15, wherein the magnetic particles comprise a paramagnetic substance or a ferromagnetic substance.

26. The system of claim 15, wherein the magnetic particles are iron oxide particles or magnetic silica particles.

27. A method for making a medical device for delivering a biologically active material to a patient comprising:

(a) providing a medical device that is insertable into the body ofthe patient which comprises a surface; (b) disposing a first coating layer comprising a biologically active material on at least a portion ofthe surface; and

(c) disposing a second coating layer comprising a polymeric material and plurality of magnetic particles on the first coating layer, wherein the second coating layer is substantially free ofthe biologically active material.

28. The method of claim 27, wherein the first coating layer is substantially free ofthe magnetic particles.

29. The method of claim 27, wherein the first coating layer further comprises a polymeric material.

30. The method of claim 29, wherein the polymeric material in the first coating layer is different than the polymeric material in the second coating layer.

31. The method of claim 27, wherein the magnetic particles have an average particle size of about 0.01 μm to about 50 μm.

32. The method of claim 31 , wherein the magnetic particles have an average particle size of about 0.01 μm to about 10 μm.

33. The method of claim 27, wherein the magnetic particles comprise a paramagnetic substance or a ferromagnetic substance.

34. The method of claim 27, wherein the magnetic particles are iron oxide particles or magnetic silica particles.

35. The method of claim 27, wherein the first coating layer further comprises magnetic particles.

36. The method of claim 35, wherein the average particle size ofthe magnetic particles in the first coating layer is different than the average particle size ofthe magnetic particles in the second coating layer.

37. The method of claim 35, wherein the concentration of the magnetic particles in the first coating layer is different than the concentration ofthe magnetic particles in the second coating layer.

38. The method of claim 35, wherein the magnetic susceptibility ofthe magnetic particles in the first coating layer is different than the magnetic susceptibility ofthe magnetic particles in the second coating layer.

39. The method of claim 27, further comprising disposing a sealing layer on the second coating layer, wherein the sealing layer comprises a polymeric material and is substantially free ofthe biologically active material and the magnetic particles.

40. The method of claim 27, wherein the medical device is a stent having a sidewall comprising a plurality of struts, and wherein the surface is part ofthe struts.