Biomedical Engineering Reference
In-Depth Information
molecular profiling of cancer markers (Her2/ neu , EGFR, and EpCAM) on human
cells was demonstrated with CLIO nanoparticles directly conjugated to monoclonal
antibodies. With the development of the second-generation NMR-2 and the
highly magnetic MnFe 2 O 4 nanoparticles, subsequent cellular detection sensitivity
was remarkably improved to approximately single-cell level, far surpassing the
sensitivity of other conventional clinical methods (Fig. 9.10 a). Furthermore, a new
assay protocol was established that reports the expression level of a specific
biomarker and the target cell density.
To independently measure cell numbers by NMR, we exploited a phenomenon
of low-grade phagocytosis of nontargeted MNPs by tumor cells [ 59 ]. When mam-
malian cells were incubated (15 min at 37 ı C) with unmodified MNPs (MNP-ˆ),
linear and cell-number-dependent R 2 changes (R 2 ) were observed (Fig. 9.10 b).
Interestingly, these changes were similar across a wide variety of cell types. The
results were fitted to Eq. 9.2 ; R 2
n C ,wherer 2 is the cellular relaxivity
for MNP-ˆ and n C is the cell concentration (N C =V). The cellular relaxivities (r 2 )
were statistically identical (p > 0:99) among different tumor cell lines, suggesting
that the method may provide a universal measure for estimating n C .
Using Eq. 9.2 and the cell density information (above), the expression level ()
of a select marker was defined as
r 2
R Ab
r Ab
r Ab
r 2
n C
R 2 D
n C D
r 2
where R Ab
2 and r Ab 2 are R 2 changes and the cellular relaxivity, respectively,
with a marker-specific MNP. In this normalized form, now reports the cellular
expression level of a targeted marker, providing a way to molecularly profile target
cells regardless of cell numbers in a sample. The method was extensively verified
by comparing NMR measurements to other standard methods (flow cytometry,
Western blotting) [ 22 , 27 , 28 ]. In one set of experiments, we measured the expres-
sion level of HER2 in breast cancer cell lines (Fig. 9.10 c). The measured HER 2
10 3 cells) showed good agreement
(R 2 >98%) with both flow cytometry (requiring
=R 2 / from NMR (requiring
10 5 cells) and Western blotting
10 7 cells), validating the analytical capability of DMR. Note that DMR
detection was much faster (
15 min) and performed using >10 2 times fewer cells.
Clinical Trial
Through the integration of the complementary DMR and BOND technologies, this
chip-based NMR detection platform has been applied in clinical trials of cancer
cell profiling [ 26 ]. A total of 50 patients with suspected abdominal malignancies
were enrolled. Each patient underwent fine-needle aspiration (FNA) using a 22-G
needle, followed by routine core biopsies (17-G needle) for conventional analysis.
The FNA samples were aliquoted and profiled for 11 predefined cellular markers:
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