Bioinstructive 3D-Printed Magnesium-Baghdadite Bioceramic Scaffolds for Bone Tissue Engineering

Current synthetic bioceramic scaffolds often lack bioinstructive ability for effective bone regeneration. We have selected magnesium-doped baghdadite (Mg-BAG) scaffolds, known for their promising osteoinductive and mechanical properties, as the base material and fabricated them using a liquid crystal display 3D printing technique. Building on this foundation, we have advanced the application of ion-assisted plasma polymerization (IAPP) technology, adapted for 3D structures, to develop homogeneous bioinstructive interfaces on these scaffolds for enhanced osteoinductive properties. The IAPP coatings formed under energetic ion bombardment maintained a strong attachment to the Mg-BAG scaffolds after 1 month of incubation at 37 °C in cell culture media. We provided evidence that such robustness of the interfaces is regulated by the coating's growth mechanism on a nanoscale, transitioning from initial island formation to a stable, smooth structure. The coatings enhanced the release of silicon ions from the scaffolds and significantly slowed the release of bone morphogenetic protein 2 (BMP2) over a period of 45 days. In the presence of lower soluble BMP2 concentrations, the biofunctionalized scaffolds demonstrated superior biocompatibility and osteoinductivity compared to those with physisorbed BMP2, as evidenced by sustained cell proliferation and elevated levels of osteogenic gene expression observed in human osteoblast-like cells (HOBs). This research highlights a key evolution of IAPP from traditional 2D substrates to more complex 3D structures and the excellent potential of IAPP bioceramic scaffolds as a next generation of cell-free constructs for bone regeneration applications and beyond.