Processing and evaluation of bioactive coatings on polymeric implants

Area of Science:

• Biomaterials Science
• Materials Engineering
• Orthopedic Technology

Background:

• Polyetheretherketone (PEEK) offers advantages over metallic implants in spinal surgery.
• Enhancing PEEK bioactivity is crucial for improving implant integration and fusion rates.
• Current methods for hydroxyapatite coating often require high temperatures detrimental to PEEK.

Purpose of the Study:

• To develop bioactive hydroxyapatite (HA) coatings on PEEK substrates for spinal implants.
• To investigate the use of an yttria-stabilized zirconia (YSZ) interlayer for thermal protection.
• To optimize post-deposition heat treatments (microwave and hydrothermal annealing) for crystalline HA formation at lower temperatures.

Main Methods:

• Radio-frequency magnetron sputtering was used to deposit YSZ and HA coatings onto PEEK.
• Plasma activation of PEEK surfaces was performed to enhance adhesion.
• Microwave and hydrothermal annealing were employed for post-deposition heat treatment.
• Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used for microstructural and compositional analysis.

Main Results:

• Plasma activation significantly improved coating adhesion strength.
• The YSZ interlayer provided effective heat shielding, preventing PEEK degradation.
• Microwave annealing resulted in a crystalline HA coating, unlike amorphous as-deposited HA.
• The crystalline YSZ layer appeared to facilitate HA crystallization, potentially acting as nucleation sites.
• Cell culture studies demonstrated significantly increased cell attachment and growth on microwave-annealed HA/YSZ/PEEK coatings.

Conclusions:

• A novel method using YSZ interlayers and microwave annealing effectively produced crystalline HA coatings on PEEK.
• This approach enhances the bioactivity and potential osseointegration of PEEK spinal implants.
• The developed coatings show promise for improving spinal fusion outcomes compared to uncoated PEEK.