The Co-Incorporation of Zn/Cu or Zn/Co Ions Improves the Bone Regeneration Potential of PEOT/PBT–βTCP Composite 3D-Printed Scaffolds

Treatment of critical-sized bone defects remains challenging despite bone's regenerative capacity. Herein, a combination of a biodegradable polymer possessing bone-bonding properties with bioactive β-tricalcium phosphate (βTCP) particles coated with osteogenic (Zinc) and angiogenic (copper or cobalt) ions has been proposed. βTCP was coated with zinc and copper (Zn/Cu) or zinc and cobalt (Zn/Co) using 15 mM (low) or 45 mM (high) metallic ion solutions. Composites were obtained by a combination of the βTCP with poly(ethylene oxide terephthalate)/poly(butylene terephthalate) (PEOT/PBT) copolymer in a 50:50 ratio. Composites were additively manufactured into 3D porous scaffolds and their osteogenic and angiogenic properties evaluated using a direct culture with human mesenchymal stromal cells (hMSCs) as well as an indirect coculture with human umbilical vein endothelial cells (HUVECs). We hypothesized that the combination of Zn/Cu or Zn/Co in the form of a coating of the βTCP particles would stimulate both osteogenic and angiogenic properties of PEOT/PBT-βTCP scaffolds. In addition, we investigated whether the resulting biomaterials influenced the paracrine function of hMSCs. Zn/Cu or Zn/Co were successfully co-incorporated into the ceramic without changing its chemistry. Scaffolds containing low concentrations of Zn/Co increased the expression of RUNX2, OCN, and OPN, while scaffolds with low concentrations of Zn/Cu enhanced the expression of ALPL. On the protein level, high Zn/Co concentrations elevated ALP and collagen production. Angiogenic properties improved with increased VEGFA expression by hMSCs and branching of tubules formed by HUVECs, particularly with low concentrations of Zn/Co. Scaffolds with high ion concentrations also increased cytokine and chemokine secretion, suggesting enhanced paracrine effects.