Surface Modification of Polyetheretherketone With Calcium Phosphate Using Ultraviolet Functionalization

Polyetheretherketone (PEEK) medical devices have been shown to perform well as permanent implants, but the hydrophobicity of PEEK limits its osseointegration ability. Postprocessing techniques are used to improve osseointegration, with ultraviolet (UV) light-assisted functionalization being one possible method. We hypothesized that UV irradiation of PEEK could be used to graft hydroxyapatite (HAp) to its surface. PEEK samples were created via fused filament fabrication and submerged in 2× simulated body fluid (SBF). Samples were exposed to a 2 W/cm² UV light for 6 h and then placed in a water bath set to 37°C for a total of 72 h. After being washed with deionized water and dried, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was performed on the functionalized samples, control PEEK samples that were not treated, and control samples that were soaked in SBF for 72 h but were not exposed to UV light. Images of the surface of the functionalized samples and controls were obtained using a scanning electron microscope with energy-dispersive spectroscopy. An in vitro cell study using mouse preosteoblasts was performed to verify if functionalization improves osteoconduction. Normalized alkaline phosphatase activity was used as a marker for osteogenic activity. Analysis revealed that UV-assisted functionalization successfully applied a layer of calcium phosphate material to the surface of the PEEK. After culturing functionalized surfaces in vitro, the addition of calcium phosphate was found to significantly improve osteogenic activity when compared to nonfunctionalized PEEK samples after 7 and 14 days.