Porous composite biomaterials and related methods

Abstract

A composite material for use, for example, as an orthopedic implant, that includes a porous reinforced composite scaffold that includes a polymer, reinforcement particles distributed throughout the polymer, and a substantially continuously interconnected plurality of pores that are distributed throughout the polymer, each of the pores in the plurality of pores defined by voids interconnected by struts, each pore void having a size within a range from about 10 to 500 μm. The porous reinforced composite scaffold has a scaffold volume that includes a material volume defined by the polymer and the reinforcement particles, and a pore volume defined by the plurality of pores. The reinforcement particles are both embedded within the polymer and exposed on the struts within the pore voids. The polymer may be a polyaryletherketone polymer and the reinforcement particles may be anisometric calcium phosphate particles.

What we claim is: 
     
         1 . A composite material, comprising:
 a porous reinforced composite scaffold, comprising:
 a polyaryletherketone polymer and anisometric reinforcement particles distributed throughout the polyaryletherketone polymer, and 
 a substantially continuously interconnected plurality of pores distributed throughout the polyaryletherketone polymer, each of the pores in the plurality of pores defined by voids interconnected by struts, each pore void having a size within a range from about 10 to 500 μm, 
   wherein a plurality of the anisometric reinforcement particles are both embedded within the polyaryletherketone polymer and exposed on the struts within the pore voids, and   wherein the porous reinforced composite scaffold has a scaffold volume that includes a material volume defined by the polyaryletherketone polymer and the anisometric reinforcement particles, and a pore volume defined by the plurality of pores.   
     
     
         2 . The composite material according to  claim 1 , wherein the porous reinforced composite scaffold is formed by mixing polymer, reinforcement, and porogen particles to obtain a substantially uniform particle mixture, compression molding the particle mixture, and removing the porogen particles. 
     
     
         3 . The composite material according to  claim 2 , wherein the particle mixture is dispersed in a non-solvating fluid, and wherein the non-solvating fluid is removed by one of vacuum, heating or a combination thereof prior to compression molding. 
     
     
         4 . The composite material according to  claim 2 , wherein each of the pores in the plurality of pores has a pore void size and shape defined by the removed porogen particles, and wherein the porogen particles are either homogenous or heterogeneous in shape and are either homogeneous or heterogeneous in size, the porogen particle size in the range from about 10 to 500 μm. 
     
     
         5 . The composite material according to  claim 2 , wherein the porogen particles are selected from the group consisting of NaCl, wax, polysaccharides, cellulose, and combinations thereof. 
     
     
         6 . The composite material according to  claim 2 , wherein the porogen particles have been removed from the porous reinforced composite scaffold material by leaching. 
     
     
         7 . The composite material according to  claim 1 , wherein the anisometric reinforcement particles are present in the polyaryletherketone polymer from about 1 to about 60% of the material volume. 
     
     
         8 . The composite material according to  claim 1 , wherein the anisometric reinforcement particles are distributed essentially uniformly throughout the polyaryletherketone polymer. 
     
     
         9 . The composite material according to  claim 1 , wherein the anisometric reinforcement particles comprise one or more of hydroxyapatite, calcium-deficient hydroxyapatite, carbonated calcium hydroxyapatite, beta-tricalcium phosphate (beta-TCP), alpha-tricalcium phosphate (alpha-TCP), amorphous calcium phosphate (ACP), octacalcium phosphate (OCP), tetracalcium phosphate, biphasic calcium phosphate (BCP), anhydrous dicalcium phosphate (DCPA), dicalcium phosphate dihydrate (DCPD), anhydrous monocalcium phosphate (MCPA), monocalcium phosphate monohydrate (MCPM), and combinations thereof, and, wherein the polyaryletherketone polymer comprises one or more of polyetheretherketone (PEEK), polyetherketonekteone (PEKK), and polyetherketone (PEK). 
     
     
         10 . The composite material according to  claim 1 , wherein the anisometric reinforcement particles comprise hydroxyapatite whiskers that have a mean aspect ratio (length along c-axis/length along a-axis) of greater than 1 and less than 100, and wherein the size of the anisometric reinforcement particles ranges between 20 nm and 2 mm. 
     
     
         11 . The composite material according to  claim 1 , wherein the pore volume ranges from about 1 to 95 percent, by volume, based on the scaffold volume. 
     
     
         12 . The composite material according to  claim 1 , wherein the porosity varies within the porous reinforced composite scaffold either from a highly porous center to a relatively dense exterior surface or from a relatively dense center to a highly porous exterior surface. 
     
     
         13 . The composite material according to  claim 1 , wherein the porous reinforced composite scaffold has a compressive elastic modulus similar to that of trabecular bone. 
     
     
         14 . A composite material, comprising:
 a porous reinforced composite scaffold, comprising:
 a polyaryletherketone polymer and anisometric reinforcement particles comprising calcium phosphate crystals distributed essentially uniformly throughout the polyaryletherketone polymer, and 
 a substantially continuously interconnected plurality of pores that are uniformly distributed throughout the polyaryletherketone polymer, each of the pores in the plurality of pores defined by voids interconnected by struts, each pore void having a size within a range from about 10 to 500 μm, and 
   wherein the porous reinforced composite scaffold has a scaffold volume that includes a material volume defined by the polyaryletherketone polymer and the anisometric reinforcement particles, and a pore volume defined by the plurality of pores, and   wherein the anisometric reinforcement particles are present in the polyaryletherketone polymer from about 1 to about 60% of the material volume, and   wherein anisometric reinforcement particles are both embedded within the polyaryletherketone polymer and exposed on the struts within the pore voids, and   wherein the porous reinforced composite scaffold is formed by mixing polymer, reinforcement, and porogen particles to obtain a substantially uniform mixture, compression molding the particle mixture at a temperature from between 20 to 400 degrees C., and removing the porogen particles.   
     
     
         15 . The composite material according to  claim 14 , wherein the particle mixture is dispersed in a non-solvating fluid, and wherein the non-solvating fluid is removed by one of vacuum, heating or a combination thereof prior to compression molding. 
     
     
         16 . The composite material according to  claim 14 , wherein the compression molding temperature is in a range from about 350 to about 375 degrees C. 
     
     
         17 . The composite material according to  claim 14 , wherein the compression molding temperature is in a range from about 365 to about 375 degrees C. 
     
     
         18 . A method for forming a porous reinforced composite scaffold, comprising:
 using a powder processing approach in conjunction with compression molding and particle leaching to prepare the composite scaffold, the process including the steps comprising:
 providing a powder mixture densified in a die, the powder mixture comprising a thermoplastic polymer powder, reinforcement particles in powder form, and porogen particles; 
 compression molding the densified powder mixture at a temperature sufficient to fuse the polymer powder to provide a sintered composite; and 
 removing the porogen particles a material from the porous reinforced composite scaffold. 
   
     
     
         19 . The method for forming a porous reinforced composite scaffold according to  claim 18 , further comprising the steps comprising;
 prior to providing the powder mixture densified in a die, first providing each of the thermoplastic polymer powder, the reinforcement particles in powder form, and the porogen particles;   dispersing, in any order, each of the thermoplastic polymer powder, the reinforcement particles in powder form, and the porogen particles in a non-solvating fluid to provide a fluid dispersion of the powder mixture;   wet-consolidating the powder mixture to remove the fluid; and   drying the wet-consolidated powder mixture.   
     
     
         20 . The method for forming a porous reinforced composite scaffold according to  claim 18 , wherein the compression molding temperature sufficient to fuse the polymer powder is in a range from about 350 to about 375 degrees C. 
     
     
         21 . The method for forming a porous reinforced composite scaffold according to  claim 18 , wherein the compression molding temperature sufficient to fuse the polymer powder is in a range from about 365 to about 375 degrees C. 
     
     
         22 . The method for forming a porous reinforced composite scaffold according to  claim 18 , wherein the thermoplastic polymer powder comprises a polyaryletherketone polymer, and wherein the reinforcement particles comprise anisometric calcium phosphate. 
     
     
         23 . A composite material, comprising:
 a porous reinforced composite scaffold, comprising:
 a thermoplastic polymer and reinforcement particles distributed throughout the thermoplastic polymer, and 
 a substantially continuously interconnected plurality of pores that are distributed throughout the thermoplastic polymer, each of the pores in the plurality of pores defined by voids interconnected by struts, each pore void having a size within a range from about 10 to 500 μm, and 
   wherein the porous reinforced composite scaffold has a scaffold volume that includes a material volume defined by the thermoplastic polymer and the reinforcement particles, and a pore volume defined by the plurality of pores, and   wherein the reinforcement particles are present in the thermoplastic polymer from about 1 to about 60% of the material volume, and   wherein reinforcement particles are both embedded within the thermoplastic polymer and exposed on the struts within the pore voids.   
     
     
         24 . The composite material according to  claim 23 , wherein the porous reinforced composite scaffold is formed by mixing thermoplastic polymer, reinforcement, and porogen particles to obtain a substantially uniform mixture, compression molding the particle mixture at a temperature from between 20 to 400 degrees C., and removing the porogen particles. 
     
     
         25 . The composite material according to  claim 23 , wherein the thermoplastic polymer is selected from the group consisting of a polyaryletherketone polymer, a bioresorbable polymer, and combinations thereof. 
     
     
         26 . The composite material according to  claim 23 , wherein the thermoplastic polymer is selected from the group consisting of polyaryletherketone (PAEK), polyetheretherketone (PEEK), polyetherketonekteone (PEKK), polyetherketone (PEK), polyethylene, high density polyethylene (HDPE), ultra-high molecular weight polyethylene (UHMWPE), low density polyethylene (LDPE), polyethylene oxide (PEO), polyurethane, polypropylene, polypropylene oxide (PPO), polysulfone, polypropylene, poly(DL-lactide) (PDLA), poly(L-lactide) (PLLA), poly(glycolide) (PGA), poly(c-caprolactone) (PCL), poly(dioxanone) (PDO), poly(glyconate), poly(hydroxybutyrate) (PHB), poly(hydroxyvalerate (PHV), poly(orthoesters), poly(carboxylates), poly(propylene fumarate), poly(phosphates), poly(carbonates), poly(anhydrides), poly(iminocarbonates), poly(phosphazenes), polymethylmethacrylate (PMMA), bisphenol a hydroxypropylmethacrylate (bis-GMA), tri(ethylene glycol) dimethacrylate (TEG-DMA), and combinations thereof. 
     
     
         27 . The composite material according to  claim 23 , wherein the reinforcement is selected from the group consisting of hydroxyapatite, calcium-deficient hydroxyapatite, carbonated calcium hydroxyapatite, beta-tricalcium phosphate (beta-TCP), alpha-tricalcium phosphate (alpha-TCP), amorphous calcium phosphate (ACP), octacalcium phosphate (OCP), tetracalcium phosphate, biphasic calcium phosphate (BCP), anhydrous dicalcium phosphate (DCPA), dicalcium phosphate dihydrate (DCPD), anhydrous monocalcium phosphate (MCPA), monocalcium phosphate monohydrate (MCPM), and combinations thereof. 
     
     
         28 . The composite material according to  claim 23 , wherein the thermoplastic polymer comprises a polyaryletherketone polymer, and wherein the reinforcement comprises anisometric calcium phosphate.