Biomedical Engineering Reference
In-Depth Information
were modified with specific antibodies that targeted the cell surface proteins
that are overexpressed in cancer cells. 287 The IOMNPs offer high surface to
volume ratio causing higher binding capacity and higher efficiency for CTC.
Compared with microbeads, a decrease in the size of the capture particles
from micrometers to nanometers increases the available adsorptive areas by
100-1000 times. While the interaction between microparticles and target cells
is a quasi-heterogeneous reaction, those between the IOMNPs and CTCs is
almost entirely homogeneous because of the small NMs size making cap-
ture faster in suspension. Additionally, magnetic microbeads are not efficient
for the separation of target cells in whole blood because of high viscosity,
high cell density, high protein content, and its generally complex composition
preventing efficient contact with the cell surface antigen. 288 Microbead mag-
netic separation of CTCs is controlled by aggregation when a large number
of microbeads accumulate on the cells causing cell detection to be difficult
especially with flow cytometry, because the size of the aggregated cells that
are captured with the microbeads affect light scattering. 289 To improve the
microbead capture of CTCs, complicated pre-treatment of blood such buffy
coat preparation and lysis of the RBCs, are necessary for success but such
preparation steps can destroy the cells, resulting in decreased number of CTCs
making the diagnosis unreliable. 285 These challenges and issues in magnetic-
microbead based capture of CTCs may be solved with the use of NPs which
are three orders of magnitude smaller in size.
NPs are small providing a higher surface to volume ratio that allows a
more efficient contact with the surface of the cells. 285 The nanoscale size
allows multiple NPs to attach on the cell surface without cell aggregation as
shown in Figure 7.10 . With these concepts, Xu and his group demonstrated
the separation of circulating cancer cells using an antibody conjugated IO
NPs (IO-Ab) under a low magnetic field gradient. 285 Using these demon-
strated the ability of the IO-Ab to capture cancer cells in spiked fresh human
whole blood without a pre-treatment process. Some of the evaluation pro-
cesses during SK-BR3 capture with IO-Ab in fresh whole human blood are
described below.
7.7.1 IO-Ab Separation of Cancer Cells in Spiked Fresh Human
Whole Blood 285
The cells were first grown following the manufacturer's recommendation
or as described in Chapter 4 Section 6.1 . The fresh female whole blood was
purchased from Biological Specialty Corporation (Colmar, PA) certified
with no hepatitis or HIV contamination. IO-Ab conjugation is as described
in Chapter 3 Section 3.1 . The following steps are recommended to per-
form IO-Ab capture of cells that are spiked in fresh human whole blood.
All the experiments involving human blood must be performed in a BSL2
laboratory.
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