Improved bone regeneration with bone targeted scaffold

The sustained release and bone tissue-specific localization of bone morphogenetic protein 2 (BMP-2) are crucial factors in overcoming the shortcomings in its clinical use. In a previous study, we introduced a bone-targeted, lipoplex-loaded, three-dimensional (3D) bioprinted bilayer scaffold, termed polycaprolactone-bioink-nanoparticle (PBN). We confirmed the bone-specific and sustained release of BMP-2 with PBN in silico and in vitro and demonstrated improved bone formation in vivo. In this study, we evaluated the bone-regenerative effect of PBN combined with bone-inducing drugs in the beagle 3-wall defect model, aiming to facilitate their stable and active application in clinical settings. Surgical defects were created on both sides of the beagle mandible after 4 weeks of teeth extraction (P2, P3, and P4), assigning four groups: (1) control, no scaffold; (2) BMP-2, BMP-2-loaded collagen; (3) PBN/BMP/5-aza-dC, BMP-2, 5-aza-2'-deoxycytidine (5-aza-dC) loaded PBN scaffold; and (4) PBN/5-aza-dC, 5-aza-dC-loaded PBN scaffold. At 4 and 8 weeks postoperatively, the beagles were sacrificed, and radiographic and histological analyses were performed. The micro-computed tomography analysis revealed that the PBN/BMP/5-aza-dC and PBN/5-aza-dC groups showed significant increases in volume density and bone mineral density between 4 and 8 weeks postoperatively (p < 0.05). The BMP-2 and PBN/BMP/5-aza-dC groups showed significantly more mineralized tissue 4 weeks postoperatively, and the largest amount of mineralized tissue was detected after 8 weeks. Based on these results, we suggest that the PBN scaffold would be a good carrier for bone-inducing drugs with bone-tissue specificity and sustained release, especially BMP-2, to reduce clinical side effects.