Figure Legends:
Figure 1: In vitro multi-modal loading system with 3D bone
mimetic scaffolds. (a) In future experiments, breast cancer cells will
be seeded in bone-mimicking scaffolds fabricated from
poly(lactide-co-glycolide) and bone mineral (hydroxyapatite). (b)
Scaffolds will be loaded in a multi-modal bioreactor system under nine
configurations of dynamic compression and direct perfusion.
Figure 2: 3D reconstruction of scaffold from microCT image and
solid-fluid assembly model. (a) The bone-mimicking scaffold is highly
porous with mean macropore size 432 μm and mean wall thickness 58 μm
(Pathi et al., 2010). (b) A scaffold was scanned using high-resolution
microCT images with voxel size 5.4 μm (Liu et al., 2018). (c) The 3D
voxel model of the scaffold (shown in ivory) as well as the fluid domain
(shown in cyan) was generated using ScanIP. The solid-fluid assembly was
a sub-domain of the whole model, with final dimensions 1.2 mm thick and
2 mm wide.
Figure 3: Multiphysics simulation model. (a) Volumetric meshes
of the fluid and solid domains were directly generated in ScanIP from 3D
voxel models. (b) Fluid and solid surface meshes formed a watertight
assembly along with shared nodes one the interior fluid-solid
interfaces. (c) Boundary conditions were assigned to match the
experimental setup. Interior fluid-solid interface was linked together
in order to transfer coupled data (i.e., solid displacements and fluid
forces).
Figure 4: Heat maps and distributions of surface principle
strain of low and high compression. (a) Surface strain contours of 5%
compression were distributed evenly in the scaffold with 70% values
located in 5,000-20,000 με range. (b) Strains of 10% compression
shifted towards higher range (10,000-40,000 με).
Figure 5: Median WSS versus time during the 1 Hz loading cycle.WSSs induced by compression alone revealed symmetrical waveforms.
However, when scaffolds were loaded with both compression and perfusion,
the waveforms became asymmetric. Peak WSS values occurred at 0.25 sec of
each cycle and increased with higher magnitude loading. WSS = wall shear
stress.
Figure 6: Cyclic compression caused dynamic interstitial fluid
flow. (a) In the C+P- simulation, velocity vectors showed fluid flow
changed direction during scaffold loading (fluid perfused out) and
unloading (fluid resorbed in). (b) In contrast, during combination
loading (shown C+P+), fluid velocity vectors at 0.25 sec showed greater
fluid flow going upward, the same as the direction of applied perfusion.
Fluid flow was much lower at 0.75 sec with some reversed velocity
vectors seen.