Decreased bacteria activity on Si3N4 surfaces compared with PEEK or titanium

Abstract

A significant need exists for orthopedic implants that can intrinsically resist bacterial colonization. In this study, three biomaterials that are used in spinal implants -titanium (Ti), polyether-ether-ketone (PEEK), and silicon nitride (Si 3 N 4 ) -were tested to understand their respective susceptibility to bacterial infection with Staphylococcus epidermidis, Staphlococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Enterococcus. Specifically, the surface chemistry, wettability, and nanostructured topography of respective biomaterials, and the effects on bacterial biofilm formation, colonization, and growth were investigated. Ti and PEEK were received with as-machined surfaces; both materials are hydrophobic, with net negative surface charges. Two surface finishes of Si 3 N 4 were examined: as-fired and polished. In contrast to Ti and PEEK, the surface of Si 3 N 4 is hydrophilic, with a net positive charge. A decreased biofilm formation was found, as well as fewer live bacteria on both the as-fired and polished Si 3 N 4 . These differences may reflect differential surface chemistry and surface nanostructure properties between the biomaterials tested. Because protein adsorption on material surfaces affects bacterial adhesion, the adsorption of fibronectin, vitronectin, and laminin on Ti, PEEK, and Si 3 N 4 were also examined. Significantly greater amounts of these proteins adhered to Si 3 N 4 than to Ti or PEEK. The findings of this study suggest that surface properties of biomaterials lead to differential adsorption of physiologic proteins, and that this phenomenon could explain the observed in-vitro differences in bacterial affinity for the respective biomaterials. Intrinsic biomaterial properties as they relate to resistance to bacterial colonization may reflect a novel strategy toward designing future orthopedic implants.

Silicon Nitride: A Synthetic Mineral for Vertebrate Biology

“…A significant amount of interest has been generated over the past decade in functionalizing biomaterial surfaces to be zwitterionic for anti-fouling purposes 12 . A surface where positive and negative charges are intimately mixed allows for extreme hydrophilicity (as observed on the current surface-treated Si 3 N 4 materials); it also prevents bacterial adhesion (as previously reported for AS Si 3 N 4 samples) 13 . Moreover, zwitterated surfaces have also been observed to induce greater apatite formation on titanium alloys 14 .…”

Strategies to Reduce Biofilm Formation in PEEK Materials Applied to Implant Dentistry—A Comprehensive Review

“…Moreover, the disease has been associated to specific immunological alterations on peri-implant crevicular fluid levels of proinflammatory, anti-inflammatory and osteoclastogenesis-related chemokines [65]. Several studies analyzed in this review [30][31][32][33][34][35] investigated biofilm and antimicrobial properties of pure PEEK, demonstrating that the polymer is susceptible to biofilm colonization. Within a context in which PEEK clinical applications in Implant Dentistry are increasing [28], strategies to modify its surface to enhance its antimicrobial/antibiofilm properties are crucial.…”

“…In vivo (human) studies did not fulfill inclusion criteria of this review. Regarding PEEK modification strategies, 6 studies analyzed pure PEEK compared to other materials [30][31][32][33][34][35] (e.g., titanium, silicon, gold, silver, zinc oxide, zirconia, silicon nitride) and none of them revealed special antibiofilm or antimicrobial properties of PEEK material. A total of 25 studies used strategies to reduce biofilm and bacterial colonization on PEEK, which were able to successfully confer either antibiofilm or antimicrobial properties, or both, to the material.…”

Comparison of anti-fouling surface coatings for applications in bacteremia diagnostics

“…19–23 Materials with different functional groups change bacterial adhesion depending on material hydrophobicity and charge. 24 For example, Chu and Williams studied the effects of physical configurations of suture materials on bacterial adhesion. 25 They showed that polydioxanone sutures exhibited slight affinity towards the adherence of Escherichia coli and Staphylococcus aureus ; however, Dexon sutures had much higher affinity towards the two bacteria.…”