Computational fluid dynamics of biomaterial inks flowing through extrusion nozzles in bioprinting of substitutes for cartilaginous tissues

Resumo

Computational fluid dynamics (CFD) can be useful to predict the behavior of biomaterials in
bioprinting in order to avoid clogging of extrusion nozzles and, in case of cell embedded biomaterials, to avoid
wasting cells. In bioprinting, cells are exposed to high shear stresses when in contact against the printing needle
walls. If the stresses exceed a limit value, cell membranes may disrupt. Biomaterial inks specially formulated for
bioprinting of substitutes for cartilaginous tissues were characterized for their rheological properties, and the
obtained data were used in fluid dynamics simulations of the flow through extrusion nozzles. Some compositions
contained powdered extracellular matrix derived from devitalized cartilage (DVC), added to give the
biochemical complexity necessary for the bioprinted material, and others contained polycaprolactone (PCL),
added to give greater mechanical resistance. The simulations indicated very high shear stresses (greater than 4
kPa) during extrusion for compositions containing PCL, which could cause cell disruption in high extent. It is
concluded that, for those compositions, the addition of cells to the scaffolds should be done preferably after
bioprinting, instead of using a cell embedded biomaterial, because cell viability after extrusion tends to be low.