Lotus root and osteons-inspired channel structural scaffold mediate cell biomineralization and vascularized bone tissue regeneration

The interconnectivity of porous scaffold is vital for cell and tissue infiltration, and vascular networks formation, determining the successful bone regeneration in large bone defects. Here, inspired by the lotus-root and Haversian system of natural bone, a nano-hydroxyapatite/polyurethane (n-HA/PU) lotus root-like scaffold inlaid with micro holes on the wall of the adjacent channel was utilized to mediate cell biomineralization and vascularized bone tissue regeneration. Such a particular lotus-type structure remarkably promoted cells to proliferate and infiltrate into the center of the entire scaffold, serving as a clue to account for regulating cell alignment and differentiation physically. In vitro studies suggested that apatite accumulated dramatically on the channel wall in the lotus-type scaffold, probably promoting specific osteogenic differentiation of cells by the orientated channels, even in the absence of osteogenic factors. In vivo creation of critical bone defects (15-mm segments) was done in the radius of rabbits and implanted with the scaffold of different geometry to assess the structural parameters on the efficacy of new bone regeneration. The more extensive positive staining of BMP-2, more considerable amount of infiltrated capillary, more robust new bone formation, particularly the biomechanical strength of lotus-type scaffold group could reach the level of the control group without surgery, indicating that the lotus-type scaffold was more favorable for new bone tissue formation along tube-like channels. These results highlighted the potential of this biomimetic scaffold for cell and tissue infiltration and thus repair large bony defects.