Masked stereolithography-based additive manufacturing of radiopaque biocomposites for enhanced imaging in potential bio-implant applications

Many medical conditions require biocompatible and biodegradable implants that are visible under non-invasive imaging. However, the inherent radiotransparency of polymer-based devices limits post-operative monitoring. This study reports a silk powder-reinforced radiopaque composite for orthopaedic and tissue engineering applications, fabricated via masked stereolithography (MSLA) with intrinsic X-ray visibility. Radiopaque ceramic fillers were incorporated at varying concentrations, and silk powder was added as a particulate reinforcement. Printed samples were characterised using X-ray imaging, contact angle goniometry, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, and mechanical testing. The composite containing 25 wt% radiopaque material, 0.5 wt% silk powder, and 0.2 wt% silane coupling agent exhibited an optimal balance of radiopacity and mechanical performance, with a tensile strength of 48.9 ± 4.0 MPa, flexural strength of 86.2 ± 1.5 MPa, and compressive strength of 292.4 ± 8.7 MPa. While high radiopaque filler loading alone reduced mechanical properties, silk compensated for this effect, preserving both structural integrity and radiographic visibility comparable to a metallic reference. Contact angle measurements indicated hydrophilic behaviour favourable for biological integration. These results demonstrate the composite’s strong potential for fabricating patient-specific, load-bearing implants that are both structurally robust and radiographically trackable, addressing a key challenge in post-operative care.