Sustainable 3D printed alginate dialdehyde-gelatin scaffolds reinforced with eggshell particles for enhanced bone regeneration

Three-dimensional (3D) printing offers a powerful route for fabricating patient-specific bone scaffolds; however, the selection of sustainable and bioactive materials remains challenging. In this study, we present a rational, two-stage approach that transforms eggshell biowaste into a mechanically robust reinforcement for alginate dialdehyde-gelatin (ADA-GEL) hydrogels. Mesoporous bioactive glass nanoparticles (MBGNPs) and eggshell particles, with and without their native membranes, were synthesized and compared in a standardized biomineralization assay. Eggshell particles exhibited markedly superior apatite formation due to their carbonate-rich composition and were incorporated into ADA-GEL bioinks to evaluate their performance as fillers for bone scaffolds. The resulting ink displayed non-Newtonian viscoelastic behavior suitable for extrusion-based 3D printing, yielding constructs with stable geometry. The presence of eggshell particles increased the elastic modulus (23 ± 14 MPa and 30 ± 7 MPa for particle-loaded scaffolds compared with 5 ± 1 MPa for the ADA-GEL construct), within the range of cancellous bone. The presence of the eggshell membrane, composed of collagenous and bioactive proteins, contributed to enhanced fluid absorption, and improved matrix hydrophilicity, while tuning the biodegradation rate (< 40% after 18 days). In vitro studies confirmed excellent cytocompatibility, supporting cell survival, adhesion, proliferation, particularly in eggshell-incorporated scaffolds and further enhanced in the presence of the eggshell membrane. All scaffolds exhibited comparable osteogenic differentiation. By establishing a streamlined materials-screening-to-biofabrication pipeline, this work introduces a sustainable and effective strategy for developing bioinspired scaffolds from natural waste for bone regeneration.