Bacteriostatic behavior of surface modulated silicon nitride in comparison to polyetheretherketone and titanium

Abstract

Perioperative and latent infections are leading causes of revision surgery for orthopaedic devices resulting in significant increased patient care, comorbidities, and attendant costs. Identifying biomaterial surfaces that inherently resist biofilm adhesion and bacterial expression is an important emerging strategy in addressing implant-related infections. This in vitro study was designed to compare biofilm formation on three biomaterials commonly employed in spinal fusion surgery-silicon nitride (Si N ), polyetheretherketone (PEEK), and a titanium alloy (Ti6Al4V-ELI) -using one gram-positive and one gram-negative bacterial species. Disc samples from various surface treated Si N , PEEK, and Ti6Al4V were inoculated with 10 CFU/mm Staphylococcus epidermidis (ATCC®14990™) or Escherichia coli (ATCC 25922™) and cultured in PBS, 7% glucose, and 10% human plasma for 24 and 48 h, followed by retrieval and rinsing. Vortexed solutions were diluted, plated, and incubated at 37 °C for 24 to 48 h. Colony forming units (CFU/mm ) were determined using applicable dilution factors and surface areas. A two-tailed, heteroscedastic Student's t-test (95% confidence) was used to determine statistical significance. The various Si N samples showed the most favorable bacterial resistance for both bacilli tested. The mechanisms for the bacteriostatic behavior of Si N are likely due to multivariate surface effects including submicron-topography, negative charging, and chemical interactions which form peroxynitrite (an oxidative agent). Si N is a new biomaterial with the apparent potential to inhibit biofilm formation. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1521-1534, 2017.

Incorporating Si3N4 into PEEK to Produce Antibacterial, Osteocondutive, and Radiolucent Spinal Implants

“…In substance, the current FTIR results support the data shown in Figure and suggest that the antibacterial effect previously reported for bulk Si 3 N 4 can be translated to PEEK by the addition of a dispersion of Si 3 N 4 particles.…”

“…Note that this study has only confirmed antibacterial effect versus a gram‐positive bacterium, while the effectiveness versus gram‐negative bacteria remains yet to be confirmed for the PEEK/β‐Si 3 N 4 composite. However, ammonia elution has proved effective also versus gram‐negative bacteria in experiments on bulk β‐Si 3 N 4 …”

“…However, the biological inertness of PEEK comes with several disadvantages. It has low bioactivity and it is prone to bacterial colonization, biofilm formation, and periprosthetic infections . These shortcomings are an unfortunate consequence of a combination of its hydrophobic character and specific molecular interactions between the bacterial proteins and PEEK's surface molecular structure in the biological environment .…”

“…With this twofold purpose in mind, a minor fraction of Si 3 N 4 particles was incorporated into a PEEK matrix. Si 3 N 4 was selected because the surface chemistry of this nonoxide bioceramic has previously demonstrated both bacterial lysis and enhanced bone formation . These properties resulted from its biologically friendly silicon/nitrogen surface chemistry and its slow elution rate which was suitable for implant applications.…”

Silicon nitride enhances osteoprogenitor cell growth and differentiation via increased surface energy and formation of amide and nanocrystalline HA for craniofacial reconstruction

“…These traits make it a material of interest for craniofacial and dental applications (Bal & Rahaman, ; Mazzocchi, Bellosi, & On, ). Studies have also shown that Si 3 N 4 is anti‐infective and enhances osteogenic differentiation of mesenchymal and osteoblast cells when compared to Ti and PEEK (Bal & Rahaman, ; Bock et al, ; Gorth et al, ; Pezzotti, McEntire, Bock, Zhu, et al, ; Webster et al, ). Chemical modifications to the surface of Si 3 N 4 enhanced its biomineralization relative to HA and other competitive biomaterials (Bock, ).…”