Tailoring polyetherketoneketone implant surfaces through natural crosslinker–assisted collagen grafting for enhancing bone regeneration while inhibiting osteoclastic activity

Abstract

Polyetherketoneketone (PEKK) is a promising implant material owing to its bone-matched elastic modulus and satisfactory mechanical performance; however, its inherent surface bioinertness limits early cell–material interactions and osseointegration, especially for the elderly with poor bone quality. Moreover, some existing surface modification strategies emphasize single osteogenic outcomes while neglecting interfacial stability and coordinated regulation of multiple cell types. In this study, a hierarchical surface engineering strategy combining physical modification with biomimetic chemical functionalization was developed to enhance PEKK bioactivity. A superhydrophilic three-dimensional porous architecture was first generated via sulfonation and atmospheric plasma treatment. Type I collagen was subsequently grafted and stabilized using natural crosslinker—procyanidin, epigallocatechin gallate (EGCG), or genipin—to construct a bioactive PEKK surface. Surface analyses demonstrated that type I collagen grafting and crosslinking preserved the porous structure while maintaining superhydrophilicity and moderate microscale roughness. Sirius Red staining and X-ray photoelectron spectroscopy confirmed enhanced type I collagen retention, with procyanidin- and genipin-crosslinked collagen coatings exhibiting superior stability compared to EGCG. Biological evaluations revealed that type I collagen-functionalized PEKK surfaces simultaneously modulated multiple bone-remodeling-related cellular responses, including enhanced migration and tube formation of human umbilical vein endothelial cells, improved adhesion, proliferation, and mineralization of human bone marrow mesenchymal stem cells, and suppression of osteoclast differentiation and activity of RAW 264.7 macrophage cells. Notably, crosslinker selection enabled functional specificity: procyanidin promoted osteogenic mineralization, whereas EGCG inhibited osteoclastic activity. Overall, this work advances PEKK surface engineering toward an integrated strategy that highlights its strong potential for orthopedic and dental implant applications requiring durable and efficient osseointegration, especially in older adults with poor bone quality.