Figure 5. Model of collagen fibers assembly over time.

As soon the osteoprogenitor cell interacts and decodes the ceramic surface (a). it synthesizes and deposits collagen molecules that resemble rods infiltrating the micropores of the HA foam. Cells are therefore induced to deposit newly formed bone tissue in a polarized fashion (b–c–d). On the other side, the nanofibrous Ha-Col sponge offers to the cells a disordered and isotropic microenvironment (e). where deposit collagen fibers in a random 3D geometry (f–g–h). Model showing collagen fibrils assembly in the extracellular matrix by the cells within a HA regular and ordered scaffold is shown (i).