Multifunctional PEEK implants: Sulfonation-polydopamine synergy for bioactivity, wear resistance, and antibacterial efficacy

PEEK is a promising biomaterial for orthopedic and dental applications due to its excellent mechanical properties, biocompatibility, and bone-like elastic modulus. However, its bioinert surface limits osseointegration and predisposes it to wear debris-induced inflammation, hindering its use in load-bearing implants. To address these challenges, this study proposes a composite modification strategy combining gradient sulfonation with polydopamine (PDA) coating to enhance the bioactivity, tribological performance, and interfacial stability of PEEK. Surface characterization revealed that sulfonation introduced porous structures and hydrophilic sulfonic acid groups, while PDA further improved wettability and enabled chelation-mediated hydroxyapatite (HA) mineralization. Tribological tests demonstrated that optimal sulfonation reduced the friction coefficient and wear width, whereas excessive sulfonation (60 min) degraded mechanical properties due to adhesive wear. In vitro mineralization confirmed that PDA-coated samples exhibited robust HA deposition, attributed to catechol/amino group-mediated nucleation. Additionally, H₂SO₄/PDA synergistically enhanced antibacterial efficacy by chemically disrupting bacterial membranes. A polyvinyl alcohol (PVA) graft layer was constructed on the surface of PEEK substrate, and its interfacial bonding performance under frictional shear load was evaluated. These results demonstrate that the H₂SO₄/PDA composite modification optimizes PEEK's multifunctional performance, offering a viable route for developing advanced biomimetic joint implants with improved osseointegration, wear resistance, and long-term stability.