Manganese-doped nano-hydroxyapatite enhances CF/PEEK osseointegration via immunomodulation-osteogenesis coupling

Abstract Carbon fiber-reinforced polyetheretherketone (CF/PEEK) exhibits great application potential in repairing bone defects, particularly in large segmental defects at load-bearing sites, due to its advantages of bone-matching mechanical properties and radiolucency. However, its inherent bioinertness tends to induce interfacial fibrosis around the implant, leading to implant loosening or even failure. Herein, we employed a liquid-phase nanoparticle self-assembly strategy to deposit a manganese-doped nano-hydroxyapatite (Mn/nHA) coating in situ on the surface of CF/PEEK, aiming to synergistically enhance the immunomodulatory capacity and bioactivity. In vitro co-culture experiments demonstrated that the Mn/nHA coating effectively induced the polarization of macrophages toward the M2 anti-inflammatory phenotype, inhibited the secretion of pro-inflammatory factors and created an immune microenvironment conducive to tissue repair. Meanwhile, it promoted the proliferation and osteogenic differentiation of BMSCs. In vivo femoral condyle defect repair experiments further confirmed that the Mn/nHA functional coating significantly inhibited interfacial fibrosis around the CF/PEEK and accelerated bone tissue regeneration, and interfacial osseointegration through an immunomodulatory-osteogenic coupling effect. This study provides new strategies and references for optimizing the bioactivity of CF/PEEK, addressing interfacial compatibility challenges and designing implant materials for bone defect repair.