PEEK Into The Future

BIOINTRAFACE® TAKES ‘PEEK’ into the Future:

Antimicrobial Silver Release from Titanium Oxide Polymer Hybrid Coated PEEK

Polyether ether ketone (PEEK) is increasingly finding use in orthopaedic applications like spinal and trauma implants. PEEK has a good combination of formability, mechanical properties, biocompatibility and radio transparency, but lacks some of the bioactive and integrative properties identified with titanium-based implants. Here we explore the use of BI metal-organic derived, hybrid coatings, as a means of creating antimicrobial treated PEEK biomaterials with a titanium oxide surface interface.

PEEK disks were coated with 100 nm thick titanium oxide and siloxane hybrid with two levels of silver oxide doping (designated Ag3072 and Ag307) (BioIntraface®, North Kingston, RI, USA). Samples were characterized and biological properties compared with non-coated PEEK controls using Scanning Electron Microscopy (SEM), water contact angle, Kirby-Bauer antibacterial testing against Staph aureus and the silver release measurements.

SEM analysis of coatings revealed micron-scale spheroids and clusters bonded within a glassy surface matrix (Fig1). ). The contact angle/hydrophobicity increased with the addition of the coating compared to bare PEEK. The water contact angle was 113.2-coating Ag3072, 100.0 for Ag307 and 84.3 for control (Fig 2). The coatings caused a large zone Staph aureus growth inhibition around the coated samples, while the bare PEEK provided no resistance to bacterial growth (Fig 3).  Increasing the coating silver concentration resulted in a similar increase in the delivery rate into the surrounding media (Fig 4).

Hybrid coatings were previously optimized for metallic applications and shown to provide durability during implantation and extraction from bone (shown below). Here we applied this technology to PEEK. Higher concentrations of silver doping introduced a brownish coloration to the PEEK, but the use of 1/10 as much silver doping produced clear coatings that still provided large zones of inhibition of bacterial growth. Hybridization enables the creation of thin-film antimicrobial titanium oxide surfaces on PEEK. This route has the potential for radio transparent implants with osseointegrative surfaces which also reduce infections and overcoming the current limitations with PEEK.

Fig 1. Scanning Electron Microscopy of BI hybrid coated PEEK, Ag 3072 (left), Ag 307 (right).

Fig 2. Large zones of bacterial inhibition were present for coatings Ag3072 (brown, top/bottom) and Ag307 (tan, left/right) compared to non-coated PEEK control (center).

Fig 3. Contact angle and hydrophobicity increased with this version of the coatings compared to bare PEEK.

Fig 4. Silver release profile of coated PEEK disks into surrounding media. Increasing the loading by 10 times, increases release by approximately the same amount.