Ex Ovo Chorioallantoic Membrane Assay as a Model of Bone Formation by Biomaterials

Biomaterials play an increasingly critical role in bone tissue engineering. However, achieving effective clinical translation requires a careful choice of biomimetic materials and thorough assessment of their efficacy and safety. Existing in vitro and in vivo models have drawbacks including time and cost constraints, invasive procedures, and discordance between animal models and clinical outcomes. Therefore, there is a demand for an alternative model. We hypothesized that the chick embryo chorioallantoic membrane can serve as a bioreactor to evaluate the initial sign of bone formation on scaffolds. In parallel, we investigated the osteogenic potential of a previously fabricated fibrin-alginate-calcium phosphate biomaterial (FACaP). Blood vessels were observed to infiltrate the scaffolds with early signs of bone formation, confirmed via RUNX-2 and alpha smooth muscle actin markers. The scaffolds' chemical composition was evaluated by Fourier-transform infrared spectroscopy, and ion chromatography was used to assess calcium ion release. Finally, the topography was examined by atomic force microscopy. In conclusion, this system offers simple refinement for in vivo models in bone tissue engineering and highlights the great potential of FACaP as an angiogenic and osteogenic biomaterial for non-load-bearing applications.