Biomedical Engineering Reference
In-Depth Information
of CNE-2 tumor cells (nasopharyngeal carcinoma cells). The results of the
T1-weighted images exhibited significant signal enhancement in the livers from
mice treated with Gd
2
O
3
@SiO
2
NPs from 15 min after injection and the signal
enhancement lasted for >24 h. The tumor xenografts exhibited increased signal
intensity starting at 30 min after injection.
Majority of the NMs undergoing development for applications as contrast
agents are made of IO NMs as shown in Table 7.4. They differ from one another
by composition such as the presence of one or more contrast generating materi-
als (para/superparamagnetic, electron density, or fluorescence), the bioactive
targeting molecules (peptides, antibodies, growth factors, receptors, NAs, etc),
the biocompatibility coating (carbohydrates, polymers, peptides, etc.), and
other surface functionalization. These NMs are generally designed and engi-
neered modularly to allow various desirable properties to be incorporated at the
best ratios. The most common nanoparticle platforms as contrast agents include
IOMNPs, non-magnetic metals such as gold, liposomes, synthetic carbon struc-
tures, polymeric NMs, and emulsions.
3
New classes are emerging with better
biocompatibility, improved targeting efficiency, higher signal, and lower levels
of toxicity.
7.7 MAGNETIC IO NP-MEDIATED CIRCULATING TUMOR
CELL ISOLATION
Cancer causes 1 in 4 deaths in the US with a total of 1,529,560 new cancer cases
annually.
282
In 2010, the 3 most commonly diagnosed types of cancer among
women in 2010 were cancer of the breast, lung, and bronchus, and colon/rec-
tum; accounting for 52% of estimated cancer cases in women. Breast cancer
was expected to account for 28% (207,090) of all new cancer cases in women
and it is the second leading cause of cancer death in women in the US.
282
Reports have indicated that circulating tumor cells (CTCs) can be found
in patients before the primary tumor is detected.
283,284
In the presence of bil-
lions of normal white blood cells (WBCs) and red blood cells (RBCs), a few
CTCs may be present in the peripheral blood during the early stage when
the primary tumor is not detectable by currently available methods.
285
Early
detection of CTCs can be sued to guide therapeutic strategies for treatment at
the early stages of cancer. But, the biggest hurdle in the detection of CTCs
is their extremely low concentration and the difficulty of separation. Human
blood consists of WBCs (3-10 × 10
6
mL
−1
), RBCs (3-9 × 10
9
mL
−1
), and plate-
lets (2.5-4 × 10
8
mL
−1
) while the number of CTCs in blood from a cancer
patient may range from 0 to 50 mL
−1
of blood
286
which means 0-50 CTCs
in 10B blood cells.
285
Because of the low levels of CTCs in blood, exist-
ing immunomagnetic cell separation techniques lack the ability to separate
the CTCs from untreated whole blood.
285
Hence, the group of Xu
285
inves-
tigated the use of IOMNPs at 30 nm diameter (
Figure 7.9
) as substitute for
the currently used micron sized magnetic beads (microbead). The IOMNPs
