Combination of 3D Printing, Plasma Polymerization, and Bioactive Coatings Towards Fabrication of Eggshell Biowaste/Polycaprolactone Composite Scaffolds for Bone Regeneration

3D printing is a robust technique that can fabricate customized tissue-engineered scaffolds for bone regeneration. Eggshell (ES) contains bone-like compounds, which makes this biowaste an interesting material for bone tissue engineering. Here, we fabricated 3D printed scaffolds using polycaprolactone (PCL) and ES powder and investigated the effect of ES concentration on the printability, mechanical properties, and morphology of the scaffolds. It was found that ES significantly alters the surface topography of the 3D printed PCL/ES structures from smooth at 10 wt.% to irregularly shaped at 30 wt.%. Moreover, although ES agglomeration was observed at higher concentrations, no significant adverse effect on mechanical properties was observed. To enhance the scaffolds' bioactivity, we used plasma polymerization to deposit an oxygen-rich thin film coating to activate the scaffolds' surfaces. Subsequently, gentamicin (Gent), as a model bioactive agent, was grafted on the surface of the scaffolds. The Gent grafting was approved by X-ray photoelectron spectroscopy. Gent-grafted scaffolds showed over 80% and 99.9% bacteria reduction against Pseudomonas aeruginosa after 1 and 24 h, respectively. Biocompatibility assessments using fibroblasts showed both high cell viability (over 90%) and cell proliferation during 23 days of culture. Using mesenchymal stem/stromal cells, successful osteoblast differentiation was observed, as shown by upregulation of Runt-related transcription factor 2 (RUNX2) and osteocalcin genes along with increased mineralization. Overall, our findings demonstrated the great potential of the 3D printed scaffolds with improved bioactivity for bone tissue engineering.