Biomedical Engineering Reference
In-Depth Information
Fig. 8.13
Avidin detection using biotinylated magnetic particles with the palm system (From Ref.
[
3
])
patients is as a pregnancy indicator, but for male patients it serves as a marker for
certain cancers, such as choriocarcinoma, germ cell tumors, and islet cell tumors.
Magnetic particles (38 nm) coated with mouse monoclonal antibody to hCG are put
into a 5
L water sample placed on the on-chip planar coil. T
2
D
169 ms in
the absence of hCG, and T
2
D
141 ms in its presence, which corresponds to the
detection of hCG. The 1-chip system detects down to 1 hCG molecule in 12 billion
water molecules.
We also detect human bladder cancer cells using the 1-chip system (Fig.
8.15
).
Magnetic particles (40 nm) coated with monoclonal antibody to bladder cancer cell
surface markers are put into a 5
L water sample placed on the on-chip coil. In
the absence of the cancer cells, the magnetic particles are monodispersed (Fig.
8.15
,
top left); in the presence of the cancer cells, magnetic particles bind to the cell
surface (Fig.
8.15
, bottom left). A following centrifugation step [
10
] separates the
cells and unbounded magnetic particles in different layers, and then the unbounded
magnetic particles are washed out. As a result, for the sample without cancer cells,
all magnetic particles are removed in the washout process, leading to a longer T
2
of
506 ms (Fig.
8.15
, top); for the sample with cancer cells, the magnetic particles that
bind to the cell surface remain, leading to a shorter T
2
of 440 ms (Fig.
8.15
, bottom).
