Osteoconductive Enhancement of Polyether Ether Ketone: A Mild Covalent Surface Modification Approach

Polyether ether ketone (PEEK, 1) is an important material for the fabrication of implants employed in spinal fusion surgery. Although its radiolucency and favorable elastic modulus have made PEEK an attractive choice for interbody fusion devices, its poor osseointegrative properties prevent the formation of a strong union between implant and surrounding bone structures and remain a major liability. Recent advancements in PEEK surface technology have resulted in improved osseointegration; however, the identification of an ideal implant material has proven challenging. In this manuscript, we describe our preliminary investigation into the realm of PEEK-based fusion devices that has culminated in the discovery of a mild, solution-based process for the preparation of covalently surface modified PEEK biomaterials that display enhanced osteoconductive properties. Surface modification occurred under mild reaction conditions via the acid-mediated addition of various commercially available hydrophilic oxyamine and hydrazine nucleophiles to the diaryl ketone moiety of PEEK. The resulting modified surfaces have been confirmed by contact angle measurements and X-ray photoelectron spectroscopy (XPS). Subsequent in vitro studies demonstrated the enhanced capability of several modified PEEK variants to promote osteogenic differentiation and mineralized calcium deposition relative to unmodified PEEK surfaces.