Biomedical Engineering Reference
In-Depth Information
Figure 11.6
Volumetric motility contrast image of a tumor spheroid that is 800
μ
m in diameter. Red denotes
high motility and blue lower motility.
by applying xenobiotics (pharmaceuticals). For instance, the motility contrast can be
used to measure the effect of anticancer drugs that influence the cytoskeleton and
prevent cell division. A series of motility contrast images were obtained for a tumor that
responded to the antimitotic drug called nocodazole. The motility contrast, 3 min after
the drug was applied, showed increased motion in the proliferating shell as a temporary
response to the drug. However, at subsequent times, the motion in the proliferating shell
is eventually quenched because many types of cellular motion are dependent on the
cytoskeleton. Nocodazole causes the microtubules to depolymerize, and hence reduces
the amount of microtubule-dependent motion. Time traces of the motility for increasing
drug doses averaged over the proliferating shell are shown in
Figure 11.7
. The drug
response is faster and stronger for high doses. Note that each curve in
Figure 11.7
is
from a different tumor spheroid. The monotonic dependence on drug dose demonstrates
the high repeatability that is achievable with the controlled growth of tumor spheroids in
a bioreactor.
11.4 Dynamic Light Scattering (DLS) Spectroscopy
The physical origin of dynamic speckle is from DLS. Although live tissues are far
from being dilute, relationships can be established between the types of motion and the
frequency dependence of the fluctuating light. DLS is caused by a change in the
optical phase of scattered light as a particle moves
[1]
. The light scattered from a
single moving particle is
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