Method for making a porous polymeric material

Abstract

Porous polymers having a plurality of openings or chambers that are highly convoluted, with each chamber being defined by multiple, thin, flat partitions are produced by a new gel enhanced phase separation technique. In a preferred embodiment, a second liquid is added to a polymer solution, the second liquid causing the solution to increase in viscosity. With sufficient polymer and second liquid present, the increase in viscosity can be up to that of a gel. The gel can then be shaped as needed. Subsequent solvent extraction leaves the porous polymeric body of defined shape. The porous polymers have utility as medical prostheses, the porosity permitting ingrowth of neighboring tissue. A second material may be incorporated into the chambers, thereby creating a microstructure filling the voids of the macrostructure. A porous polymeric body manufactured by this process may incorporate biologically active agents, and which agents may be delivered in a time-staged delivery manner, where differing drugs may be delivered over differing periods.

1 - 36 . (canceled) 
     
     
         37 . A process for creating a porous polymeric body of desired shape, comprising the steps of:
 a. selecting a polymer, wherein said polymer is a biocompatible and implantable polymer;   b. identifying a first solvent that is capable of substantially dissolving a solid form of the polymer;   c. identifying a gelling agent that does not substantially dissolve the polymer in solid form, but instead merely swells the solid polymer;   d. providing at least sufficient first solvent to said polymer as to substantially dissolve the polymer in the first solvent to form a solution;   e. adding a quantity of the gelling agent to the solution, whereupon an entire volume of the solution begins to gel;   f. continuing the adding of the gelling agent until a viscosity of the gel increases to a point where the gel is suitable for shape-forming;   g. shape-forming the gel; and   h. removing the first solvent and gelling agent from the gel.   
     
     
         38 . The process of  claim 37 , wherein forming of the polymer gel comprises spreading the gel onto an open smooth or textured surface. 
     
     
         39 . The process of  claim 37 , wherein forming of the polymer gel comprises injecting the gel into a mold. 
     
     
         40 . The process of  claim 37 , wherein forming of the polymer gel comprises spreading or injecting the gel over a three-dimensional object, and removing the three-dimensional object after removing the first solvent and the gelling agent from the gel. 
     
     
         41 . The process of  claim 37 , wherein forming of the polymer gel involves forcing a three-dimensional object into a volume of the gel, and removing the three-dimensional object after removing the first solvent and the gelling agent from the gel. 
     
     
         42 . The process of  claim 37 , wherein the porous polymer body additionally comprises a biologically active agent. 
     
     
         43 . The process of  claim 42 , wherein said biologically active agent is incorporated within the porous polymer body by one of: being mixed with the polymer and first solvent prior to addition of the gelling agent; being, mixed with the gelling agent prior to addition to the first solvent/polymer solution; being mixed with the gel prior to removal of the first solvent and gelling agent; and being incorporated within the pores of the polymeric body after removal of the first solvent and gelling agent. 
     
     
         44 . The process of  claim 42 , wherein the biologically active agent is selected from one or more of the following: physiologically acceptable drugs, surfactants, ceramics, hydroxyapatites, tricalciumphosphates, antithrombogenic agents, antibiotics, biologic modifiers, glycosaminoglycans, proteins, hormones, antigens, viruses, cells or cellular components. 
     
     
         45 . The process of  claim 37 , wherein the gel is placed in contact with a separate body, after which the first solvent and gelling agent are removed, leaving the porous polymer mechanically bound to the body. 
     
     
         46 . The process of  claim 37 , wherein the polymer comprises a biocompatible, implantable polyurethane. 
     
     
         47 . The process of  claim 46 , wherein the first solvent comprises at least one solvent selected from the group comprising dimethyl acetimide, n-methyl pyrrolidinone and tetrahydrofuran. 
     
     
         48 . The process of  claim 46 , wherein the first solvent comprises tetrahydrofuran, and the gelling agent comprises at least one liquid selected from the group comprising benzene, p-dioxane, dimethyl sulfoxide and xylene. 
     
     
         49 . A process for creating a composite body comprising a porous polymeric body using a gel enhanced phase separation technique, the process comprising the steps of:
 a. substantially dissolving a selected polymer in a suitable first organic solvent to form a solution;   b. adding a suitable gelling agent to the solution that causes an entire volume of the solution to thicken into a gel;   c. placing the gel in contact with at least one other material; and   d. removing the first solvent and gelling agent, thereby leaving a porous polymer and the at least one other material, wherein said porous polymer and said at least one other material are mechanically bound to each other.   
     
     
         50 . The process of  claim 49 , wherein the other material is biodegradable. 
     
     
         51 . The process of  claim 49 , wherein the other material provides reinforcement to the porous polymer. 
     
     
         52 . The process of  claim 51 , wherein the other material is in the form of reinforcing threads or reinforcing rings. 
     
     
         53 . The process of  claim 49 , wherein the porous polymeric body comprises a prosthesis, and further wherein said other material aids in attaching the prosthesis to host tissue. 
     
     
         54 . The process of  claim 50 , wherein the other material is in the form of a suture, tack, or biologically active agent. 
     
     
         55 . The process of  claim 54 , wherein the other material is a biologically active agent selected from one or more of the following: physiologically acceptable drugs, surfactants, ceramics, hydroxyapatites, tricalciumphosphates, antithrombogenic agents, antibiotics, biologic modifiers, glycosaminoglycans, proteins, hormones, antigens, viruses, cells or cellular components. 
     
     
         56 . The process of  claim 49 , wherein the composite body is a component of a larger body. 
     
     
         57 . The process of  claim 49 , wherein the selected polymer comprises a polyurethane. 
     
     
         58 . The process of  claim 57 , wherein the first solvent comprises at least one solvent selected from the group comprising dimethyl acetimide, n-methyl pyrrolidinone and tetrahydrofuran. 
     
     
         59 . The process of  claim 57 , wherein the first solvent comprises tetrahydrofuran, and the gelling agent comprises at least one of benzene, p-dioxane, dimethyl sulfoxide and xylene. 
     
     
         60 . The process of  claim 37 , wherein the biocompatible and implantable polymer comprises at least one polymer selected from the group consisting of polyureas, polyethylenes, polyesters and fluoropolymers. 
     
     
         61 . The method of  claim 37 , wherein said first solvent comprises an organic solvent selected from the group consisting of acetone, chloroform, p-dioxane, methylene chloride, n,n-dimethyl acetimide, dimethyl sulfoxide, 1-methyl-2-pyrrolidone, tetrahydrofuran, toluene, m-xylene, o-xylene, and methyl-ethyl-ketone. 
     
     
         62 . The method of  claim 37 , wherein said gelling agent comprises an organic solvent selected from the group consisting of acetone, chloroform, p-dioxane, methylene chloride, n,n-dimethyl acetimide, dimethyl sulfoxide, 1-methyl-2-pyrrolidone, tetrahydrofuran, toluene, m-xylene, o-xylene, and methyl-ethyl-ketone, and benzene. 
     
     
         63 . A process for creating a porous polyurethane body, comprising the steps of:
 a. dissolving a biocompatible solid polyurethane polymer in a suitable first solvent to create a solvent/polyurethane solution;   b. adding a suitable gelling agent to the solution, thereby causing an entire volume of the solution to thicken into a gel;   c. forming the gel into a desired shape; and   d. removing the first solvent and gelling agent from the gel, thereby leaving behind a shaped, porous biocompatible polyurethane body suitable for implantation.