Tissue-engineered implants for bone regeneration require consideration regarding their osteogenic and vascularization potential. Different geometries, such as biomimetic designs and lattices, can influence the mechanical properties and the vascularization capacity of bone-mimicking implants. To test vascularisation the chick chorioallantoic membrane assay is a cost effective and time-efficient alternative to small animal models. The assay can be used within boundaries to ensure less discomfort and suffering compared to fully mature animals such as mice, rats, or rabbits [1].
Sacrificial printing is a versatile technique which enables the production of bone-mimicking scaffolds in design complexities that are unable to be directly extrusion printed with a basic 3D printer [2]. In this study, different scaffold motifs (logpile, Voronoi, and trabecular bone) were fabricated via sacrificial printing in polycaprolactone to determine the effect of geometrical design on stiffness and vascularization potential. The same designs, in a polycaprolactone scaffold only, or combined with gelatin methacryloyl, were then assessed for their ability to allow the infiltration of blood vessels in a chick chorioallantoic membrane assay.
The trabecular bone design was significantly stiffer then the logpile and Voronoi when dimensions and porosity were matched (25.93 ± 4.16, 10.44 ± 6.71, 12.61 ± 5.71 MPa, respectively). Interestingly, the gelatin methacrylolyl alone did not allow new chorioallantoic membrane tissue or blood vessels to infiltrate within its structure. Only polycaprolactone on its own or when combined with gelatin methacrylolyl allowed tissue and vessel infiltration in all scaffold designs. Of the three designs, the trabecular bone design showed the greatest mineralized matrix production, collagen type I and osteocalcin expression.
This study reinforces the hypothesis that both biomaterial choice and scaffold motifs are crucial components when designing a scaffold for bone regeneration and that the chick chorioallantoic membrane assay is suitable for multi-material scaffolds.