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Orthopaedic Proceedings
Vol. 101-B, Issue SUPP_5 | Pages 116 - 116
1 Apr 2019
COMPOUNDED PEEK-SINTERED SILICON NITRIDE COMPOSITE EXHIBITS ENHANCED OSTEOCONDUCTIVITY AND RESISTANCE TO BIOFILM FORMATION
Bock R Pezzotti G Zhu W Marin E Rondinella A Boschetto F McEntire B Bal BS
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Introduction

Support of appositional bone ingrowth and resistance to bacterial adhesion and biofilm formation are preferred properties for biomaterials used in spinal fusion surgery. Although polyetheretherketone (PEEK) is a widely used interbody spacer material, it exhibits poor osteoconductive and bacteriostatic properties. In contrast, monolithic silicon nitride (Si3N4) has shown enhanced osteogenic and antimicrobial behavior. Therefore, it was hypothesized that incorporation of Si3N4 into a PEEK matrix might improve upon PEEK's inherently poor ability to bond with bone and also impart resistance to biofilm formation.

Methods

A PEEK polymer was melted and compounded with three different silicon nitride powders at 15% (by volume, vol.%), including: (i) α-Si3N4; (ii) a liquid phase sintered (LPS) ß-Si3N4; and (iii) a melt-derived SiYAlON mixture. These three ceramic powders exhibited different solubilities, polymorphic structures, and/or chemical compositions. Osteoconductivity was assessed by seeding specimens with 5 × 105/ml of SaOS-2 osteosarcoma cells within an osteogenic media for 7 days. Antibacterial behavior was determined by inoculating samples with 1 × 107 CFU/ml of Staphylococcus epidermidis (S. epi.) in a 1 × 108/ml brain heart infusion (BHI) agar culture for 24 h. After staining with PureBlu™ Hoechst 33342 or with DAPI and CFDA for SaOS-2 cell adhesion or bacterial presence, respectively, samples were examined with a confocal fluorescence microscope using a 488 nm Krypton/Argon laser source. Images were also acquired using a FEG-SEM in secondary and backscattered modes on gold sputter-coated specimens (∼20–30Å). Hydroxyapatite (HAp) deposition was measured using a laser microscope. Raman spectra were collected for samples in backscattering mode using a triple monochromator using a 532 nm excitation source (Nd:YVO4 diode-pumped solid-state laser).