Momentum - The Magazine for Virginia Tech Mechanical Engineering Vol. 3 No. 3 Fall 2018 | Page 23

Figure 4
Cell invasion in single recoil, chain and collective modes is
regulated by both diameter and spacing of nanofibers.
that’s exactly what cells are doing in our bodies.”
As cells move they pick paths by sending out a protrusion, and if the
cell finds what it needs, the protrusion matures and the cell moves in that
direction. Nain and his collaborators set up a platform to study protrusions
as cells migrate.
“Now we can see the protrusion in the direction of migration as well as
lateral protrusions independent of direction of migration,” Nain said. “Be-
cause our system can elicit lateral protrusions of varying sizes and shapes in
a controlled manner, we can study them individually to see how they form,
how they mature, and what length they extend to. The big question we can
then answer is, are all protrusions across all cell types the same?
“We have pioneered ‘Protutyping’, a new method based upon biophysical
metrics that can distinguish protrusive behavior across disease models and
cell types in a controlled and repeatable manner. Using a human breast can-
cer model, we found that the length of protrusions was longer in cancerous
cells compared to non-cancerous counterparts; and that breast cancer cells
were more sensitive to the diameter of the fiber, than say, a brain cancerous
cell,” Nain said. “You can’t really compare the two types of cells, but the sen-
sitivity was there.” To understand fiber curvature contributions to protru-
sion formation, Behkam group designed flat ribbon fibers that matched the
circumference of round fibers, thus providing a direct comparison between
flat and round geometry. They found that on flat ribbons of varying widths,
cells formed protrusions of a universal size, whereas on round fibers, the
protrusion sizes and lengths varied with diameter. Because the protrusions
are sensitive to diameter, it’s important that they be observed and studied in
vitro with round fibers of diameters found inside the body.
MOMENTUM
FALL 2018
PAGE 23