The network in B2B mimics as much as possible the physiological vascular network found in the real tissues, both in the breast and the bone side. One of the strengths and most innovative aspects is the fact that its vessels branch out and change the diameter (see news on mesoscale).
Another feature that brings the device closer to its physiological counterpart is the endothelialisation of the vessels: endothelial cells cover their surfaces making such vessels fully biological. The cells are actually included only after the manufacturing process, once the template is removed (see news on additive manufacturing).
The flow supported by the B2B network will be calibrated as close as possible to the physiological one, with a similar flow rate and shear stress on the covering cell. Otherwise, several problems might arise: turbulence effects and blood clots might cause the formation of micro-thrombi, or a higher flow rate might lead to bulged vessels thus provoking a synthetic-like form of an aneurism. Special care is needed at the level of the bifurcations, as the blood that flows through these regions has a more turbulent flow and the impact on these areas is more vigorous.
Other types of complexity instead fall outside the scope of the B2B project. For the time being in the project, the circulating fluid in the network will be a mix of culture media: the ones typically used in the breast and bone compartments and a classical media that maintains the endothelial cells alive and functional. The resulting media should be able to transport possible metastasis from breast to bone. As a possible future improvement, the cultural media could be substituted with blood, which would increase the physiological biomimicry of the B2B device, but would also bring more challenges related to studying the possible occurring of clotting. For as much as this is an important challenge to tackle in implantable synthetic vascular grafts, it remains of less importance for 3D in vitro models.