A dual-functional biodegradable composite coating fabricated on sulfonated PEEK <i>via</i> vacuum cold spraying: immunomodulation-driven osteointegration

Polyetheretherketone (PEEK) is a promising orthopedic implant alternative to metals due to its bone-mimetic modulus and biocompatibility; yet, its bioinert nature often triggers fibrous encapsulation and impedes osteointegration. Here, a biodegradable calcium silicate/β-tricalcium phosphate (CS/TCP) composite coating was fabricated on sulfonated PEEK (SP) <i>via</i> vacuum cold spraying to address these limitations. The CS/TCP coating exhibited robust bonding strength, enhanced hydrophilicity, and sustained release of Ca/Si ions, fostering apatite deposition in simulated body fluid. This bioactive interface promoted an immunomodulatory microenvironment by polarizing macrophages toward the anti-inflammatory M2 phenotype. Synergistically, ionic release and cytokine secretion enhanced MC3T3-E1 cell adhesion, proliferation, and osteogenic differentiation. <i>In vivo</i>, CS/TCP-SP reduced fibrous tissue thickness in a rat air-pouch model and improved bone-implant integration in rabbit cranial defects. The scalable coating strategy transforms inert PEEK into a bioactive, immunoregulatory implant, demonstrating potential to mitigate aseptic loosening and revision surgeries.