Antibacterial polyetheretherketone implants immobilized with silver ions based on chelate-bonding ability of inositol phosphate: Processing, material characterization, cytotoxicity, and antibacterial properties

We developed a novel antibacterial implant by forming a hydroxyapatite (HAp) film on polyetheretherketone (PEEK) substrate, and then immobilizing silver ions (Ag⁺) on the HAp film based on the chelate-bonding ability of inositol phosphate (IP6). First, the PEEK surface was modified by immersion into concentrated sulfuric acid for 10 min. HAp film was formed on the acid-treated PEEK via the soft-solution process using simulated body fluid (SBF), urea, and urease. After HAp coating, specimens were immersed into IP6 solution, and followed by immersion into silver nitrite solution at concentrations of 0, 0.5, 1, 5 or 10 mM. Ag⁺ ions were immobilized on the resulting HAp film due to the chelate-bonding ability of IP6. On cell-culture tests under indirect conditions by Transwell®, MC3T3-E1 cells on the specimens derived from the 0.5 and 1 mM Ag⁺ solutions showed high relative growth when compared with controls. Furthermore, on evaluation of antibacterial activity in halo test, elution of Ag⁺ ions from Ag⁺-immobilized HAp film inhibited bacterial growth. Therefore, the above-mentioned results demonstrated that specimens had both biocompatibility and strong antibacterial activity. The present coating therefore provides bone bonding ability to the implant surface and prevents the formation of biofilms in the early postoperative period.