Nanofiber reinforcement of attached hydrogels

Abstract

Described herein are hydrogels attached to a base with the strength and fatigue comparable to that of cartilage on bone and methods of forming them. The methods and apparatuses described herein may achieve an attachment strength between a hydrogel and a substrate equivalent to the osteochondral junction. In some examples the hydrogel may be a triple-network hydrogel (such as BC-PVA-PAMPS) that is attached to a porous substrate (e.g., a titanium base) with the shear strength and fatigue strength equivalent to that of the osteochondral junction.

What is claimed is: 
     
         1 . A method of attaching a hydrogel to a surface so that the hydrogel is secured to the surface with a shear strength of greater than 1 MPa, the method comprising:
 bonding a dry nanofiber network to the surface; and   infiltrating the bonded nanofiber network with the hydrogel, to form a multi-network hydrogel, wherein the multi-network hydrogel is secured to the surface with a shear strength of greater than 1 MPa.   
     
     
         2 . The method of  claim 1 , wherein bonding comprises cementing. 
     
     
         3 . The method of  claim 1 , further comprising mechanically polishing an outer surface of the hydrogel to a roughness of less than 30 microns. 
     
     
         4 . The method of  claim 1 , wherein infiltrating the nanofiber network with hydrogel comprises molding the hydrogel so that an outer surface of the hydrogel has a roughness of less than 30 microns. 
     
     
         5 . The method of  claim 1 , wherein bonding the dry nanofiber network comprises cementing a freeze-dried nanofiber network. 
     
     
         6 . The method of  claim 1 , wherein the dry nanofiber network comprises a cellulose nanofiber network. 
     
     
         7 . The method of  claim 1 , wherein dry nanofiber network comprises at least one of: electrospun polymer nanofibers, poly(vinyl alcohol) (PVA) nanofibers, aramid nanofibers, Aramid-PVA nanofibers, wet-spun silk protein nanofiber, chemically crosslinked cellulose nanofiber, or polycaprolactone (PCL) fibers. 
     
     
         8 . The method of  claim 1 , further comprising rehydrating the nanofiber network. 
     
     
         9 . The method of  claim 1 , wherein infiltrating comprises infiltrating the nanofiber network with a hydrogel comprising one or more of: polyvinyl alcohol (PVA) and poly(2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt (PAMPS). 
     
     
         10 . The method of  claim 1 , wherein infiltrating comprises infiltrating the nanofiber network with a double-network hydrogel comprising one or more of: poly-(N,N′-dimethyl acrylamide) (PDMAAm), copolymers of 1-vinylimidazole and methacrylic acid, amphiphilic triblock copolymers, polyampholyte hydrogels, a PVA-tannic acid hydrogel, a poly(N-acryloyl) glycinamide hydrogel, polyacrylic acid-acrylamide-C18 hydrogel, Guanine-boric acid reinforced PDMAAm, polyelectrolyte hydrogels, a poly(acrylonitrile-co-1-vinylimidazole) hydrogel (e.g., a mineralized poly(acrylonitrile-co-1-vinylimidazole) hydrogel), a polyacrylic acid-Fe3+-chitosan hydrogel, a poly(methacrylic acid) gel, a Graphene oxide/Xonotlite reinforced polyacrylamide (PAAm) gel, a poly(stearyl methacrylate)-polyacrylic acid gel, an annealed PVA-polyacrylic acid hydrogel, supramolecular hydrogels from multiurea linkage segmented copolymers, polyacrylonitrile-PAAm hydrogel, a microsilica reinforced DMA gel, a Agar-polyhydroxyethylmethacrylate gel, a polyfacryloyloethyltrimethylammonium chloride hydrogel, a poly(-(methylacryloylamino)propyl-trimethylammonium chloride hydrogel, a poly(sodium p-styrenbesulfonate) hydrogel, a polyethylene glycol diacrylate hydrogel, a polyethylene glycol hydrogel, or hydrogels composed of a combination of these polymers. 
     
     
         11 . The method of  claim 2 , wherein cementing comprises extending a cement at least 5 microns into the nanofiber network from the surface. 
     
     
         12 . The method of  claim 2 , wherein cementing comprises bonding the nanofiber network without bonding the hydrogel. 
     
     
         13 . The method of  claim 1 , further comprising mineralizing at least a portion of the nanofiber network adjacent to the surface. 
     
     
         14 . The method of  claim 2 , wherein cementing the dry nanofiber network to the surface comprises cementing the dry nanofiber network to the surface, wherein the surface is greater than 40% porous to a depth of 1 mm or greater. 
     
     
         15 . The method of  claim 2 , wherein cementing comprises applying an α-TCP cement. 
     
     
         16 . The method of  claim 2 , wherein cementing comprises applying a cement comprising one or more of: zinc oxide eugenol, glass ionomer, calcium silicate, polycarboxylate cement, zinc phosphate, and resin-modified glass ionomer cement. 
     
     
         17 . A method of attaching a hydrogel to a surface of an implant so that the hydrogel is secured to the surface with a shear strength of greater than 1 MPa, the method comprising:
 bonding a dry nanofiber network to the surface, wherein the surface is a porous surface of the implant;   rehydrating the nanofiber network;   infiltrating the nanofiber network with a hydrogel to form a multiple-network hydrogel on the surface; and   forming an outer surface of the hydrogel to a roughness of less than 30 microns.   
     
     
         18 . The method of  claim 17 , wherein forming comprises mechanically polishing an outer surface of the hydrogel. 
     
     
         19 . The method of  claim 17 , wherein forming comprises molding an outer surface of the hydrogel. 
     
     
         20 . The method of  claim 17 , wherein bonding comprises cementing. 
     
     
         21 . A method of attaching a hydrogel to a surface of an implant so that the hydrogel is secured to the surface with a shear strength of greater than 1 MPa, the method comprising:
 bonding a freeze-dried cellulose nanofiber network to the surface, wherein the surface is a porous surface of the implant;   rehydrating the freeze-dried cellulose nanofiber network;   infiltrating the freeze-dried cellulose nanofiber network with a hydrogel comprising polyvinyl alcohol (PVA) to form a multiple-network hydrogel with the freeze-dried cellulose nanofiber network on the porous surface; and   forming an outer surface of the hydrogel to a roughness of less than 30 microns.