Method of manufacturing antimicrobial implants of polyetheretherketone
Inventors
Crudden, Joseph J. • HAFIZ, JAMI • Deaton, James E. • Pepper, John R. • Johns, Derrick
Assignees
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Publication Number
US-8821912-B2
Publication Date
2014-09-02
Expiration Date
Abstract
Methods of fabricating implantable medical devices, preferably with PEEK, having antimicrobial properties, are disclosed. The antimicrobial effect is produced by incorporating ceramic particles containing antimicrobial metal cations into molten PEEK resin, which is subsequently allowed to cool and set in its final shape achieved by injection molding, cutting and machining or other techniques.
Core Innovation
The invention relates to fabricating a load-bearing spinal antimicrobial implant using polyetheretherketone (PEEK) in combination with a metal zeolite. The method includes drying polyetheretherketone resin to a residual moisture content of less than 0.1% moisture by weight, heating the dried resin to a temperature effective to melt the resin, blending in a metal zeolite that is also dried to a residual moisture content of less than 0.1% moisture by weight, cooling the blend, and forming the blend into the spinal implant.
The invention addresses moisture and oxidation control during processing, emphasizing drying of both the PEEK resin and the metal zeolite to prevent voids and metal oxidation. The disclosed approach uses blending into molten PEEK followed by cooling and forming, with the moisture-controlled melt blending of a dried metal zeolite intended to preserve antimicrobial metal cations within the implant.
In the described implementations, the antimicrobial metal zeolite includes antimicrobial metal cations, such as silver zeolite, with additional disclosed selectable metals including silver, copper, zinc, mercury, tin, lead, gold, bismuth, cadmium, chromium, or thallium. The resulting antimicrobial implant is described as exhibiting antimicrobial performance against E. coli and S. aureus, with additional described properties including radiopacity, improved cell attachment via negatively charged silicates, and additional options such as optional porosity and optional carbon-fiber reinforcement.
Claims Coverage
The independent claim set covers a method for making a load-bearing spinal antimicrobial implant, centered on moisture-controlled PEEK and dried metal zeolite blending, cooling, and forming. Inventive features focus on drying to <0.1% residual moisture, melting and blending dried metal zeolite into molten PEEK, cooling, and forming into a spinal implant; dependent claim refinements add specific temperature ranges, selectable metal-zeolite compositions, blending equipment, and material porosity options.
Moisture-controlled drying of PEEK resin and metal zeolite
Drying polyetheretherketone resin to a residual moisture content of less than 0.1% moisture by weight and drying a metal zeolite to a residual moisture content of less than 0.1% moisture by weight.
Melting and blending dried metal zeolite into molten PEEK
Heating the dried polyetheretherketone resin to a temperature effective to melt the resin and blending into the molten resin a metal zeolite.
Cooling and forming into a load-bearing spinal implant
Cooling the blend and forming the blend into the spinal implant.
Load-bearing spinal implant fabrication with specified melt temperature range
Heating said dried polyetheretherketone resin to a temperature effective to melt said resin in a range of about 360 to about 400°C.
Load-bearing spinal implant fabrication with specified PEEK drying temperature range
Drying the resin by heating it to a temperature between about 120°C and 130°C.
Metal component selection for the metal zeolite
Selecting the metal component of the metal zeolite from silver, copper, zinc, mercury, tin, lead, gold, bismuth, cadmium, chromium, or thallium.
Twin-screw extruder blending of the molten resin and metal zeolite
Performing the blending step in a twin screw extruder.
Porosity range for porous polyetheretherketone used in the method
Using polyetheretherketone having a porosity between 50% and 85% by volume.
Across the independent claim (and its dependent refinements), the claim coverage concentrates on making a load-bearing spinal antimicrobial implant by drying PEEK resin and a dried metal zeolite to <0.1% residual moisture, melting PEEK, blending in the dried metal zeolite, cooling, and forming. Refinements specify processing temperature ranges, selectable metal-zeolite metals, twin-screw extruder blending, and a quantitative porous PEEK porosity range.
Stated Advantages
Provides antimicrobial performance with up to approximately six-log reduction against E. coli and S. aureus (as described).
Provides radiopacity at low silver-zeolite loading (as described).
Improves cell attachment via negatively charged silicates (as described).
Improves or supports antimicrobial and surface-related performance, including surface roughness and silver-elution optimization (as described).
Allows optional porosity (50–85% by volume) in the implant (as described).
Allows optional carbon-fiber reinforcement (as described).
Documented Applications
A load-bearing spinal antimicrobial implant.
Antimicrobial testing against E. coli and Staphylococcus aureus (as described).
Osteoblast cell attachment assessment related to negatively charged silicates (as described).
Radiopacity assessment, including comparison to barium sulfate (as described).
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