Surface Biofunctionalization of Additively Manufactured Medical-Grade PEEK by GelMA Grafting for Maxillofacial Reconstruction

Polyetheretherketone (PEEK) is increasingly attractive for patient-specific maxillofacial reconstruction because its elastic modulus approximates cortical bone, it is fully radiolucent, and it is compatible with additive manufacturing; its principal limitation is bioinertness, as the hydrophobic surface does not support protein adsorption or direct bone apposition. This study aimed to render the surface of fused-deposition-modelling (FDM)-printed, medical-grade PEEK bioactive while preserving these bulk advantages. To this aim, 3D printed specimens of implant-grade PEEK were activated by CO₂ plasma and coated with gelatin methacryloyl (GelMA) via EDC/NHS coupling followed by UV photocrosslinking. Surfaces were characterized by attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy, sessile-drop water contact angle measurement, gravimetric analysis, and scanning electron microscopy (SEM). Plasma treatment introduced oxygen-containing functional groups and reduced the water contact angle from 78.3° to 6.6°. Covalent GelMA grafting was confirmed by characteristic amide bands, was most pronounced for the 50 mg/mL formulation, and corresponded to a deposited mass of 11.81 ± 0.47 µg/mm²; SEM revealed a relatively uniform protein film along the printed filaments. These results establish a reproducible route toward bioactive, patient-specific PEEK maxillofacial implants.