Implantable medical devices made from polymer-bioceramic composite

Abstract

Methods and devices relating to polymer-bioceramic composite implantable medical devices are disclosed.

1 . A method of fabricating an implantable medical device comprising: 
 processing a plurality of agglomerated bioceramic particles with a non-reactive surface modifier, the non-reactive surface modifier reducing the agglomeration;    forming a composite with the processed bioceramic particles, the composite including the processed bioceramic particles dispersed within a polymer; and    fabricating an implantable medical device from the composite.    
   
   
       2 . The method according to  claim 1 , wherein the non-reactive surface modifier lowers the surface energy of the particles.  
   
   
       3 . The method according to  claim 1 , wherein the processing comprises dispersing the bioceramic particles in a solution including the non-reactive surface modifier.  
   
   
       4 . The method according to  claim 1 , wherein the processing comprises mixing a suspension having the non-reactive surface modifier and the plurality of bioceramic particles so that the agglomeration is reduced.  
   
   
       5 . The method according to  claim 1 , wherein forming the composite comprises processing a mixture of the polymer and the processed particles with a shear stress higher than the fracture strength of clusters of agglomerated bioceramic particles so that agglomeration is further reduced.  
   
   
       6 . The method according to  claim 1 , wherein forming the composite comprises processing a mixture of the polymer and the processed particles with a twin-screw extruder or a kneader in such a way that agglomeration is further reduced.  
   
   
       7 . The method according to  claim 1 , wherein the non-reactive surface modifier is selected from the group consisting of stearic acid, polyethylene oxide-b-polypropylene oxide-b-polyethylene oxide, and polyethylene oxide-b-polylactide.  
   
   
       8 . The method according to  claim 1 , wherein the medical device is a stent.  
   
   
       9 . The method according to  claim 1 , wherein the polymer is biodegradable.  
   
   
       10 . The method according to  claim 1 , wherein the bioceramic particles are nanoparticles.  
   
   
       11 . The method according to  claim 1 , wherein a ratio of the weight percent of the bioceramic particles to the polymer is at least about 1:200.  
   
   
       12 . The method according to  claim 1 , wherein the bioceramic particles are selected from the group consisting of calcium sulfate and hydroxyapatite.  
   
   
       13 . A method for fabricating an implantable medical device comprising: 
 forming a suspension solution including a fluid, a non-reactive surface modifier, a polymer and bioceramic particles, wherein the polymer is dissolved in the fluid, and wherein the bioceramic particles are dispersed in the solution;    removing all or substantially all of the fluid to form a composite mixture, wherein the composite mixture comprises the bioceramic particles dispersed within the polymer, wherein the non-reactive surface modifier reduces the agglomeration of the bioceramic particles in the suspension solution and/or during formation of the composite mixture; and    fabricating an implantable medical device from the composite mixture.    
   
   
       14 . The method according to  claim 13 , wherein the fluid is removed by evaporating the fluid.  
   
   
       15 . The method according to  claim 13 , wherein the non-reactive surface modifier lowers the surface energy of the particles.  
   
   
       16 . The method according to  claim 13 , further comprising mixing the suspension solution having the non-reactive surface modifier and the plurality of bioceramic particles to facilitate reducing the agglomeration.  
   
   
       17 . The method according to  claim 13 , further comprising processing the composite with a shear stress higher than the fracture strength of clusters of agglomerated bioceramic particles so that agglomeration is further reduced.  
   
   
       18 . The method according to  claim 13 , further comprising processing the composite with a twin-screw extruder or a kneader in such a way that agglomeration is further reduced.  
   
   
       19 . The method according to  claim 13 , wherein the non-reactive surface modifier is selected from the group consisting of stearic acid, polyethylene oxide-b-polypropylene oxide-b-polyethylene oxide, and polyethylene oxide-b-polylactide.  
   
   
       20 . The method according to  claim 13 , wherein the medical device is a stent.  
   
   
       21 . The method according to  claim 13 , wherein the polymer is biodegradable.  
   
   
       22 . The method according to  claim 13 , wherein the bioceramic particles are nanoparticles.  
   
   
       23 . The method according to  claim 13 , wherein a ratio of the weight percent of the bioceramic particles to the polymer is at least about 1:200.  
   
   
       24 . A stent comprising: 
 a structural element including a bioceramic/polymer composite, the composite having a plurality of bioceramic particles dispersed within a polymer, a non-reactive surface modifier being on a surface of at least some of the particles, wherein the surface modifier reduces agglomeration of the bioceramic particles prior to and during the formation of the composite.    
   
   
       25 . The device according to  claim 24 , wherein the non-reactive surface modifier is selected from the group consisting of stearic acid, polyethylene oxide-b-polypropylene oxide-b-polyethylene oxide, and polyethylene oxide-b-polylactide.  
   
   
       26 . The device according to  claim 24 , wherein the medical device is a stent.  
   
   
       27 . The device according to  claim 24 , wherein the polymer is biodegradable.  
   
   
       28 . The device according to  claim 24 , wherein the bioceramic particles are nanoparticles.  
   
   
       29 . The device according to  claim 24 , wherein a ratio of the weight percent of the bioceramic particles to the polymer is at least about 1:200.  
   
   
       30 . A method of fabricating an implantable medical device comprising: 
 processing a mixture of a polymer and agglomerated bioceramic particles to form a composite of the bioceramic particles dispersed within the polymer, wherein the processing subjects the plurality of bioceramic particles to a shear stress higher than a fracture strength of clusters of the agglomerated bioceramic particles so that agglomeration is reduced; and    fabricating an implantable medical device from the composite.    
   
   
       31 . The method according to  claim 30 , wherein the polymer and the agglomerated bioceramic particles are processed with a twin-screw extruder or a kneader.  
   
   
       32 . The method according to  claim 30 , wherein the medical device is a stent.  
   
   
       33 . The method according to  claim 30 , wherein the polymer is biodegradable.  
   
   
       34 . The method according to  claim 30 , wherein the bioceramic particles are nanoparticles.  
   
   
       35 . The method according to  claim 30 , wherein a ratio of the weight percent of the bioceramic particles to the polymer is at least about 1:200.  
   
   
       36 . The method according to  claim 30 , wherein the bioceramic particles are selected from the group consisting of calcium sulfate and hydroxyapatite.  
   
   
       37 . A method of fabricating an implantable medical device comprising: 
 processing a mixture of a polymer and bioceramic particles to form a composite, wherein the bioceramic particles have been treated with a non-reactive surface modifier that reduces the fracture strength of clusters of the bioceramic particles, the composite comprising the bioceramic particles dispersed within the polymer; and    fabricating an implantable medical device from the composite.    
   
   
       38 . The method according to  claim 37 , wherein the non-reactive surface modifier lowers the surface energy of the particles.  
   
   
       39 . The method according to  claim 37 , wherein the agglomerated bioceramic particles are treated by dispersing the bioceramic particles in a solution including the non-reactive surface modifier.  
   
   
       40 . The method according to  claim 37 , wherein the processing subjects the composite to a shear stress higher than fracture strength of clusters of untreated bioceramic particles so that the agglomeration is reduced.  
   
   
       41 . The method according to  claim 37 , wherein the processing subjects the composite to a shear stress higher than the fracture strength of clusters of the treated bioceramic particles so that the agglomeration is reduced.  
   
   
       42 . The method according to  claim 37 , wherein the composite is processed in a kneader or a twin screw extruder.  
   
   
       43 . The method according to  claim 37 , wherein the non-reactive surface modifier is selected from the group consisting of stearic acid, polyethylene oxide-b-polypropylene oxide-b-polyethylene oxide (PEO-b-PPO-b-PEO), and polyethylene oxide-b-polylactide.  
   
   
       44 . The method according to  claim 37 , wherein the medical device is a stent.  
   
   
       45 . The method according to  claim 37 , wherein the polymer is biodegradable.  
   
   
       46 . The method according to  claim 37 , wherein the bioceramic particles are nanoparticles.  
   
   
       47 . The method according to  claim 43 , wherein the bioceramic particles are selected from the group consisting of calcium sulfate and hydroxyapatite.