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 functionalize the surface of fused-deposition-modeling (FDM)-printed, medical-grade PEEK to increase its potential for bioactivity while preserving these bulk advantages. To this end, 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°. GelMA deposition following EDC/NHS coupling, consistent with covalent immobilization, was supported by characteristic amide bands and was most pronounced for the 50 mg/mL formulation, corresponding 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 surface-functionalization route and provide preliminary physicochemical indicators of potential bioactivity for patient-specific PEEK implants, to be confirmed through in vitro and in vivo biological validation.