DNA aptamer immobilized hydroxyapatite for enhancing angiogenesis and bone regeneration.

In this study, we developed aptamer-conjugated hydroxyapatite (Apt-HA) that promotes bone regeneration and angiogenesis. The 3R02 bivalent aptamer specific to vascular endothelial growth factor (VEGF) was grafted to the hydroxyapatite (HA) surface. Apt-HA was tested for its VEGF protein capture ability to determine the optimal aptamer concentration immobilized on the HA. Apt-HA showed higher VEGF protein capture ability, and faster growth of human umbilical vein endothelial cell (HUVEC) compared to a neat HA with no cytotoxic effects on human osteoblasts. To examine in vivo angiogenesis and bone regeneration, Apt-HA and HA were bilaterally implanted into rabbit tibial metaphyseal defects and analyzed after eight weeks using micro-CT, histology, and histomorphometry. Apt-HA showed significantly increased the volume of new bones, the percentage of bone, and the density of bone mineral in cortical bone. Apt-HA also exhibited the enhanced bone formation at the cortical region in a histomorphometric analysis. Finally, Apt-HA showed significantly increased blood vessel number compared to a neat HA. In summary, the engineered Apt-HA has potential as a bone graft material that may simultaneously promote bone regeneration and angiogenesis. STATEMENT OF SIGNIFICANCE: This work presents a functional hydroxyapatite bone graft using a DNA-based aptamer which overcomes the limitations of existing bone graft materials, which use bound signaling peptides. DNA aptamer immobilized hydroxyapatite enhances the in vitro proliferation of human umbilical vascular endothelial cells as well as in vivo angiogenesis and bone regeneration. DNA aptamer immobilized hydroxyapatite shows no cytotoxic effect on human osteoblasts.

Repair of rabbit radial bone defects using bone morphogenetic protein-2 combined with 3D porous silk fibroin/ß-tricalcium phosphate hybrid scaffolds.

Our study aimed to investigate the effect of bone morphogenetic protein-2 (BMP-2) bound to silk fibroin and ß-tricalcium phosphate (SF/ß-TCP) hybrid on the healing of critical-size radial defects in rabbits. A 15-mm critical-size defect was induced at mid-diaphysis in the left radius of 20 New Zealand white rabbits (average age, 3.5 months; weight, 2.5-3.0 kg). The animals were randomized into Group 1 (SF/ß-TCP combined with BMP-2), Group 2 (SF/ß-TCP alone), and Group 3 (nothing implanted). Radiographs were obtained every 2 weeks and euthanasia was performed after 8 weeks for visual, radiological, micro-computed tomography (micro-CT), and histological studies. Eight weeks after implantation (SF/ß-TCP combined with BMP-2), radiographs showed that new bone formed on the surface of the implant and had bridged the defect in Group 1. Micro-CT imaging also confirmed the formation of new bone around the implant, and the newly formed bone was quantified. Histological examination revealed newly formed bone in the implanted area. Meanwhile, there was no formation of new bone in Group 3. Among the groups, most active formation of new bones was found in Group 1, while there was no difference between Group 2 and Group 3. Based on these results, we concluded that BMP-2-SF/ß-TCP showed significant improvement in healing of critical-size defects. Therefore, the combination of BMP-2 and SF/ß-TCP would be useful in the field of bone tissue engineering.