title: Mechanical and in vitro investigation of a porous PEEK foam for medical device implants.
abstract: OBJECTIVE
  Implantable-grade polyetheretherketone (PEEK-OPTIMA®) is a high-performance thermoplastic that has been used in implant devices such as spinal-fusion cages since its introduction in 1999. Here, a new porous PEEK version was investigated.
  
  
  METHODS
  Porous PEEK was fabricated using industrial scale relevant methods of compounding with porogen filler, extrusion, and subsequent extraction with water at supercritical temperatures and pressures. Mechanical properties were assessed according to ISO standards. Marrow stromal cells were cultured on porous PEEK samples and in vitro cytocompatibility was assessed by total DNA, alkaline phosphatase activity, osteopontin, calcium, and cell morphology to indicate stages of proliferation, differentiation, and mineralization. Compressive strength was assessed statically on 21 day cell cultures and media-soaked samples and dynamically within a medical device application specific context for interbody fusion cages (ASTM F2077).
  
  
  RESULTS
  Manufacturing resulted in a biomaterial with ~50% porosity and a mean pore size of 100 microns. The porous PEEK was found to have: tensile strength (14.5MPa), strain at break (3.5%), impact strength (3.6 kJ/m2), flexural strength (21.6MPa), and flexural modulus (0.8GPa). Production of extracellular mineralized matrix occurred very early in the culture period, indicating a preferred surface for differentiation. SEM images revealed polygonal cell morphology supporting a differentiated osteoblastic-like phenotype. EDS analysis detected levels of carbon, phosphorus, and calcium coinciding with assay results for the proliferation and differentiation stages.
  
  
  CONCLUSIONS
  Previous observations of cytocompatibility and calcification on the PEEK biomaterial could be carried through to this new porous form of the PEEK biomaterial. This helps porous PEEK to potentially offer more design options for implant devices requiring reduced modulus and/or increased tissue ingrowth aspects at the surface.
authors: School of Chemical, Biological and Materials Engineering, University of Oklahoma Bioengineering Center, University of Oklahoma, Norman, OK - USA.
authors: Bonnie C
authors: BC
authors: Landy
authors: Samuel B
authors: SB
authors: Vangordon
authors: Peter S
authors: PS
authors: McFetridge
authors: Vassilios I
authors: VI
authors: Sikavitsas
authors: Marcus
authors: M
authors: Jarman-Smith
mesh_terms: D000818:Animals; D001577:Benzophenones; D001854:Bone Marrow Cells / Q000166:cytology / Q000502:physiology; D002478:Cells, Cultured; D007659:Ketones / Q000737:chemistry*; D008297:Male; D008422:Materials Testing; D055595:Mechanical Phenomena; D011092:Polyethylene Glycols / Q000737:chemistry*; D011108:Polymers; D016062:Porosity; D019736:Prostheses and Implants; D051381:Rats; D017208:Rats, Wistar; D013123:Spinal Fusion / Q000295:instrumentation; D013314:Stress, Mechanical; D017154:Stromal Cells / Q000166:cytology / Q000502:physiology; D013718:Tensile Strength / Q000502:physiology; D054457:Tissue Scaffolds / Q000737:chemistry; D055682:Viscoelastic Substances / Q000737:chemistry
chemical_list: D001577:Benzophenones; D007659:Ketones; D011108:Polymers; D055682:Viscoelastic Substances; C063834:polyetheretherketone; D011092:Polyethylene Glycols