Page 236 - Bio Engineering Approaches to Cancer Diagnosis and Treatment

9.3 Microfluidic systems in cancer 235

with low conductivity. Also, CTC isolation using the dielectrophoresis technic is
reported in recent studies [64].
Cancer cell separation using acoustic waves (acoustofluidics) is a new way that
has been reported in the past few years. An ultra-high-throughput acoustophorestic
microdevice, that was able to remove RBCs from human whole blood with 95% effi-
ciency, was described by Adams et al. As well, acoustofluidic technology can be used
to separate prostate cancer cells from WBCs in blood. Yang and Soh have utilized
acoustofluidics in MCF7 breast cancer to sort of viable cells from nonviable [65,66].
Nevertheless, cell separation based on acoustic-wave is still in the early stages of
research and needs more development and optimization [59]. Novel progress tech-
nologies will able the molecular characterization of CTCs and the definition of bio-
markers for therapeutic strategies and knowledge of the process of cancer metastasis.
Thus implementing CTC analyses as a liquid biopsy using microfluidic lab-on-a-
chip medical devices can give new insights into anticancer drug mechanisms.
In recent years, many microfluidic platforms in order to CTC detection and isola-
tion based on size were presented. The performance of a microfluidic device which
enables to capture LNCaP-C4-2 prostate cancer cells with efficiency more than 95%,
in such a way that operates under constant pressure at the inlet for blood samples. It
creates a uniform pressure differential across all the microchannels in the array. Opti-
mization of rows to achieve a capture of more than 95% demonstrated that trapping
chambers with five or six rows of microconstriction is needed. The shape of cancer
cells deformed in the constriction channel. The blood flow temporarily decreased
because of cancer cell deformation [62].
CTC measurement is a cancer screening method with a minimum invasion that
is useful for the early staging of cancer patients and in monitoring recurrent or meta-
static disease. In order to attain decisive results for CTC detection and enrichment,
generally, ∼7.5 mL of blood volume is needed due to rare enumeration of CTCs in
the blood (1–100 cells/mL). A limitation of the current CTC enumeration systems
approved by the US Food and Drug Administration (FDA) namely CellSearchR and
AdnaTestR. According to the result of clinical studies, CTC detection in blood in
cases of breast cancer, colorectal cancer, and prostate cancer patients can be done by
CellSearch [62].
The necessity of having minimal sample preprocessing is ideal for CTC isolation
and enrichment that can avoid loss of CTC and it should have high throughput, high
efficiency, high sensitivity, high purity, and low cost. Because of considering these
criteria and in order to eliminate the limitations associated with surface-marker-
based approaches, the microfluidics has been motivated to develop new CTC tech-
nologies based on the biophysical properties of CTCs. These rely on the assumption
that biophysical attributes such as size, deformability, permittivity, and conductivity
of CTCs are different from blood cell properties. Microchips based on size exclu-
sion, deformability, and dielectrophoresis have been explored and shown promising
results in CTC collection [67,68]. Also, SAWs that are generated by tilted identical
IDTs on microfluidic channels were utilized to CTCs collection of whole blood.
For CTC enrichment, finding of balance between capture efficiency, throughput, and