Nanostructured Calcium Phosphate Scaffolds Trigger Osteoinduction and Osteogenesis

Objectives: To evaluate the effect of nanostructure and macropore architecture on the intrinsic osteoinduction of a new family of biomimetic CaP materials in an ectopic site, and to correlate it with the osteogenic potential when implanted in bone.
Methods: Four types of implants resulted from combining two different architectures and nanostructures were compared: 1) Fine-Foams (FF) 2) Fine-robocasted (FR) 3) Coarse-Foams (CF) 4) Coarse-robocasted (CR). Intramuscular (epaxial muscles) and intraosseous (5 mm Ø monocortical femur defect) implantation was performed in beagle dog (n=6 per implant/ 2 time points). Newly formed bone was assessed by backscattered scanning electron microscopy and quantified through microscopic computed tomography as a % of the total implant volume for intramuscular samples and as a % of the total cortical bone defect volume for the intraosseous samples.
Results: In the intramuscular study, new ectopic lamellar bone formation was observed only in FF group (4/6 animals, % of bone volume = 2.06 ± 1.84) at 6 weeks and in FF (6/6 animals, 14.64 ± 6.15%) and CF (2/6 animals, 0.58 ± 1.32%) groups at 12 weeks. Table 1 show the osteogenesis obtained.
Conclusions: The in vivo performance of biomimetic CaP scaffolds with identical chemical composition (CDHA) was highly dependent on macropore geometry (Concave/Prismatic) and nanoscale surface topography (Needle/Plate-like crystals). A concave geometry of macropores combined with high SSA (needle-like crystals) stimulates the intrinsic osteoinduction, this resulting in an enhancement of the osteogenic potential when implanted in bone.