Abstract:
A coating can be applied to an endolumenal wall of a medical device by positioning an optical fiber within the lumen, providing a photo-activated chemical to contact the endolumenal wall, supplying the optical fiber with radiation capable of activating the chemical within the lumen, and withdrawing the optical fiber from the lumen at a controlled rate while the radiation is being emitted from the optical fiber to activate the chemical in close proximity to the endolumenal wall.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based on and claims all benefits of U.S. Provisional Ser. No. 60/582,694 filed Jun. 24, 2004. 
     
    
     BACKGROUND  
       [0002]     1. Technical Field  
         [0003]     The present invention relates to medical devices, particularly surgical instruments and prostheses, having elongated and generally opaque wall structures surrounding an elongated lumen such as catheters, introducers, needles, stent frames and stent grafts. The invention particularly relates to methods and apparatus for applying selected coatings to endolumenal surfaces of such devices.  
         [0004]     2. General Background  
         [0005]     Catheters, introducers, and other similar medical devices having elongated lumens are used to deliver diagnostic and therapeutic agents and appliances to remote locations through the vascular systems within the body of a patient. Needles, stent frames, stent grafts and other similar medical devices have elongated, although, generally, proportionally somewhat shorter lumens that are used to provide a pathway for vital fluids to and through the tissue and vascular systems of the patent. Further, when expanded radially, stent frames have a more or less porous structure rather than the substantially continuous wall character of the other medical devices considered herein.  
         [0006]     Considerable attention has been given to controlling the physical interaction between such devices and the various structures and fluids through which the devices are moved by manipulating the surface chemistry of various portions of the devices. For example, U.S. Pat. No. 6,706,025 to Engelson, et al., discloses coating various longitudinal segments of the exterior surface of a catheter with lubricious hydrophilic polymers selected to provide various frictional characteristics to the different longitudinal segments. The selected polymeric coatings are applied by spraying a solution or suspension of the polymers or of oligomers of the monomers onto the catheter, or by dipping the catheter into the solution or suspension after sealing the open ends of the catheter. The coating is allowed to dry. During or after drying, the coating can be irradiated with ultra-violet light or ionizing radiation to promote polymerization and cross-linking of the coating to the exterior surface of the catheter. The coating procedure can optionally be repeated so that one or more additional coatings are applied in a similar manner. No means are disclosed to specifically apply any coating liquids to the endolumenal wall of the catheter. No means are disclosed to provide irradiation to encourage the polymerization of any coating fluids that might accidentally flow into the lumen of the catheter. As a result, the interior surface chemistry of the catheter is essentially totally unaffected by the procedures and chemical agents disclosed in Engelson.  
         [0007]     Other processes for coating stent frames are known from including brushing, wiping, pad printing, ink-jet printing, electrostatic liquid spraying, and electrostatic powder coating. The desirability of coating stent frames with a polymer dissolved in a solvent optionally containing a therapeutic substance such as actinomycin D, paclitaxel, docetaxel, or rapamycin is known. Known polymers that can be used to coat stents with such substances include, for example, a number of polymethacrylates, polycaprolactone, and polysilanes. The therapeutic substances can also be anti-neoplastic agents, anti-proliferative agents, anti-inflammatory agents, growth control factors, antibiotics, antioxidants, and combinations thereof.  
         [0008]     However, there remains a need for methods and apparatus to apply a desired surface chemistry to the endolumenal walls of catheters, introducers, needles, stent frames, stent grafts, and other similarly structured medical devices, to achieve the recognized benefits of such modifications in surface chemistry. There is a particular need to coat the endolumenal walls or surfaces of stent frames and stent grafts with substances that will effectively inhibit targeted adverse physiological reactions, such as restenosis, caused by uncoated surfaces of medical devices inserted or implanted in a patient&#39;s body.  
       BRIEF SUMMARY  
       [0009]     Apparatus for applying a coating to an endolumenal wall of a medical device includes an optical fiber dimensioned to fit within the lumen of the medical device. The optical fiber must be capable of carrying radiation having a suitable wavelength to interact with a chemical agent of the coating material to be applied to the endolumenal wall. The optical fiber must have a first end that is able to be coupled to a source of such radiation. The source of radiation can include intensity controls to govern the amount of radiation to be delivered to the optical fiber first end.  
         [0010]     The optical fiber desirably has a second end with a structure conducive to illuminate the endolumenal wall adjacent to the second end of the optical fiber. The optical fiber second end can take the form of a divergent lens that causes radiation passing through the second end to be spread onto that portion of the endolumenal surface that is beyond the optical fiber second end. The optical fiber second end can also take the form of an inwardly protruding conical reflective surface that causes radiation to be reflected outward through the side wall of the optical fiber.  
         [0011]     A coating material supply provides at least a monomolecular film of the coating material immediately adjacent to the optical fiber second end. The coating material supply can take the form of a reservoir of the coating material of a size suitable to permit the medical device to be at least partially immersed in the coating material. The coating material supply can also take the form of a pump coupled to a reservoir of the coating material and to the medical device in such a manner as to permit a flow of the coating material to be supplied to and/or through the lumen of the device. The coating material supply can also take the form of a source of the coating material to a capillary space between the optical outer surface and the endolumenal wall, the capillary force being relied upon to distribute the coating material to a position adjacent to the optical fiber second end. A flow of gas can be used to inhibit excessive coating.  
         [0012]     The second end of the optical fiber desirably travels at least once through at least the length of any portion of the lumen to which the coating material is to be applied. The second end of the optical fiber can travel through the entire length of the lumen at a controlled rate of speed, which can vary from segment to segment of the lumen. The rate of speed can be related to the amount of optical energy needed to cause a desired reaction of the photo-active component of the coating material. Suitable position and drag sensors can be included to aid in the control of the traveling characteristics of the optical fiber with respect to the lumen.  
         [0013]     A coating can be applied to an endolumenal wall of a medical device by positioning an optical fiber within the lumen, providing a photo-activated chemical to contact the endolumenal wall, supplying the optical fiber with radiation capable of activating the chemical within the lumen, and withdrawing the optical fiber from the lumen at a controlled rate while the radiation is being emitted from the optical fiber to activate the chemical in close proximity to the endolumenal wall. This method can be modified or repeated as desired to achieve a coating of desired character and thickness. The exact chemical make-up and characteristics of the coating material is not central to the present case, which is directed to apparatus and methods for applying coatings of various character to the endolumenal wall of a medical device, except that the coating material must have a component that reacts to the radiation carried by the optical fiber.  
         [0014]     The previously described method and apparatus, and the attributes and characteristics of same, will be better understood from the following detailed description, when read in conjunction with the accompanying drawings, wherein like reference characters refer to like parts throughout the several views and different embodiments of the present invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a cross-sectional view of a first embodiment of a distal end of an apparatus of the present invention.  
         [0016]      FIG. 2  is a cross-sectional view of a second embodiment of a distal end of an apparatus of the present invention.  
         [0017]      FIG. 3  is a cross-sectional view of a proximal end of an apparatus of the present invention.  
         [0018]      FIG. 4  is a block diagram of an apparatus of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]     Apparatus  10  for applying a coating to an endolumenal wall  12  of a medical device  14  is shown in  FIG. 1 . The medical device  14  can be, for example, a catheter, introducer, needle, stent frame or stent graft. The apparatus  10  includes an optical fiber  16  having a distal end  18 . The optical fiber  16  is surrounded by an opaque wall  20 . The opaque wall  20  can be further surrounded by a fluid-carrying channel  22  having a distal end  24 . An outer wall  26  can surround the fluid-carrying channel  22 . A plurality of openings  28  can be provided in the outer wall  26  adjacent to the distal end  24  of the fluid-carrying channel  22 . The outer wall  26  can also be opaque to radiation having a suitable wavelength to interact with a chemical agent of the coating material to be applied to the endolumenal wall. The distal end  18  of the optical fiber  16  is configured to disperse any radiation traveling down the optical fiber  16  onto the endolumenal wall  12  of the medical device  14 . The optical fiber  16  must be capable of carrying radiation having a suitable wavelength to interact with a chemical agent of the coating material to be applied to the endolumenal wall  12 . The configuration of the distal end  18  can be a simple divergent lens shape  30  that will disperse the light in a well known manner to interact with any fluid  32  that may be dispensed onto the endolumenal wall  12  through the openings  28 .  
         [0020]     The fluid  32  can include lubricious hydrophilic polymers, such as, for example, a polysiliane or a polyfluoroethylene selected to provide various frictional characteristics. The fluid  32  can also include, for example, a therapeutic substance such as actinomycin D, paclitaxel, docetaxel, or rapamycin. The fluid  32  can also include, for example a solvent such as, for example, water, alcohol or ether. The fluid  32  can also include, for example, therapeutic substances can also be antineoplastic agents, antoproliferative agents, anti-inflammatory agents, growth control factors, antibiotics, antioxidants, and combinations thereof. The fluid  32  must have a component that reacts to the radiation from the distal end  18  of the optical fiber  16 . Suitable radiation reactive components include, for example, anthraquinone, benzophenone, thioxanthone, and acetophenone.  
         [0021]     An alternative structure for the apparatus  10  is shown in  FIG. 2  wherein the distal end  18  of the optical fiber  16  can include an inwardly protruding conical surface  34 . The conical surface  34  can be formed to reflect any radiation traveling down the optical fiber so that the radiation is directed radially outward through side wall  36  to interact with any fluid  32  that may be dispensed onto the endolumenal wall  12  through the openings  28 . The openings  28  can be spaced around the outer wall  26  in any pattern that will permit at least a monomolecular film of the fluid  32  to be dispensed onto the endolumenal wall  12 . When the wall  12  of the medical device  14  is continuous, the thickness of the film of fluid  32  can be controlled by providing a flow a gas between the outer wall  26  and the endolumenal wall  12 . The flow of gas between the outer wall  26  and the endolumenal wall  12  can also act as a centering mechanism for the apparatus  10  within the medical device  14 , which may contribute to a more uniform distribution of the fluid  32 . The outer wall  26  of the apparatus  10  can be dimensioned to fit within, but be movable with respect to, the endolumenal wall  12  of the medical device  14 . The outer wall  26  can be dimensioned to define a capillary space between the outer wall  26  and the endolumenal wall  12  to aid in the transport of the fluid  32  out of the channel  22  and onto the endolumenal wall  12 .  
         [0022]     The apparatus  10 , of either  FIG. 1  or  FIG. 2 , can also include a proximal end  38  as shown in  FIG. 3 . The proximal end  38  can include a liquid inlet bushing  40  that surrounds the optical fiber  16 . A molded fitting  42  can couple the bushing  40  to the outer wall  26 . The inlet bushing includes an opening  41  for receiving the fluid  32  from a source described below. The optical fiber  16  can pass through an end wall  44  of the bushing  40  toward a suitable source of radiation having a suitable wavelength to interact with a chemical agent of the coating material to be applied to the endolumenal wall. The bushing  40 , including the end wall  44 , can also be opaque to radiation having a suitable wavelength to interact with the reactive chemical agent of the coating material. The end wall  44  can be coupled to the opaque wall  20  with an O-ring or other seal  45  to prevent the fluid  32  from leaking from the bushing  40  around the opaque wall  20 .  
         [0023]     The apparatus  10  can include a plenum  43  that can be coupled to an end  13  of the medical device  14 . The plenum  43  can include an inlet  39  coupled to a source of gas, which can be air or another gas such as, for example, nitrogen, that is pressurized sufficiently to cause a longitudinal flow of gas between the outer wall  26  and the endolumenal wall  12  of the medical device  14 . The gas can be selected to have a vapor component that will contribute to the development of a uniform thickness of the film of fluid  32 . The plenum  43  can include an end wall  37  having an opening  35  for receiving the optical fiber  16 , opaque wall  20  and outer wall  26 . A seal  33  can be provided between the opening  35  and outer wall  26  to prevent escape of the gas through the opening  35 .  
         [0024]     The apparatus  10  is schematically shown in  FIG. 4  to include an optical fiber  16  coupled to a source  46  of radiation of a suitable wavelength to interact with the chemical agent of the coating material. The radiation source  46  can include an intensity control  48  to govern the amount of radiation to be delivered to the optical fiber. The radiation source  46  can also include a wavelength tuning or selection control  50  for selecting radiation of a suitable wavelength for interaction with the chemical agent of the coating material. The apparatus  10  can include a supply  52  of liquid containing a coating material to be applied to the endolumenal wall  12 . The liquid supply  52  can include a reservoir  54  and a pump  56 . The liquid supply  52  can be connected to the bushing  40  shown in  FIG. 3 . A gas supply  68  can supply a flow of a gas to the plenum  43  in sufficient quantity to cause a flow of gas longitudinally between the endolumenal wall  12  and the optical fiber  16 . The apparatus  10  can also include a traction device  58  for causing longitudinal movement between the optical fiber  16  and the endolumenal wall  12  of the medical device  14 . The traction device  58  can be coupled to or include a motor  60  with a speed control  62  for regulating the rate of relative movement between the optical fiber  16  and the medical device  14 . The traction device  58  can also be coupled to a position sensor  64 , a drag sensor  66 , and other controls for sensing and governing the rate of movement, application of the liquid, and application of radiation.  
         [0025]     Using an apparatus like those disclosed in the preceding figures, a coating can be applied to an endolumenal wall of a medical device in a variety of related processes that can include the steps of positioning an optical fiber with a distal end within the lumen, providing a photo-activated chemical in contact with the endolumenal wall adjacent to the optical fiber distal end, supplying the optical fiber with radiant energy of a wavelength selected to interact with the photo-activated chemical, and moving the optical fiber with respect to the lumen at a controlled rate during the photo activation. The process steps can be repeated as often as necessary to deposit the desired amount of photo-activated chemicals on the endolumenal wall. The process steps can be practiced over the entire length of a selected device or limited to only selected regions within the lumen.  
         [0026]     The foregoing detailed description should be regarded as illustrative rather than limiting, and the following claims, including all equivalents, are intended to define the spirit and scope of this invention.