Enhancing PEEK surface bioactivity: Investigating the effects of combining sulfonation with sub-millimeter laser machining
Slila Chayanun, Theerapat Chanamuangkon, Budsaraporn Boonsuth, Aldo R. Boccaccini, Boonrat Lohwongwatana
Abstract
Due to its superior mechanical properties and chemical stability, Polyetheretherketone (PEEK) has emerged as an alternative to conventional metal implants. However, the bio-inertness of PEEK's surface has limited its applications. Ambient sulfonation has been adopted to enhance bioactivity, but its nanoscale topographic changes are insufficient for implant-bone interlock. To further improve bone-implant interlock, this study employs CO2 laser machining to create sub-millimeter (0.5 mm) grooves on PEEK's surface, aiming to encourage bone ingrowth and strengthen the implant-bone interface. This research investigated the physical and chemical properties and bio-interaction of PEEK surface modified by sulfonation (SPEEK), laser machining (L-PEEK), and combination of both technique (L-SPEEK). X-ray photoelectron spectroscopy (XPS) spectra revealed that sulfonation compensates for the surface chemical shift instigated by laser ablation, aligning the surface chemistry of L-SPEEK with that of SPEEK. Furthermore, L-PEEK surfaces presented pores with sizes ranging from 1 to 600 μm, while SPEEK surfaces exhibited pores between 5 and 700 nm. All tested samples demonstrated non-cytotoxicity, with L-SPEEK exhibiting the highest mineralization and ALP activity as 2 and 2.1 times that of intrinsic PEEK, after 21 days of incubation. Microscopic imaging reveals a notably higher extracellular content on L-SPEEK compared to the other groups. This study underscores the potential of combining sub-millimeter laser machining with sulfonation in enhancing early osteogenic markers, providing a promising pathway for future PEEK-based orthopedic applications.