Biomedical Engineering Reference
In-Depth Information
(a)
(b)
Figure 2.7
(a) A lateral fl ow device. The liquid
sample (drops) releases magnetic labels from
the conjugate pad, after which the analyte
molecules bind to the labels as they migrate
(in the direction of the arrow) towards the
test line (TL). At the TL, the labels bind to
capture molecules in proportion to the
amount of analyte in the sample. The device
is then inserted into a reader; (b) A plan-view
showing part of lateral fl ow device located
above an array of coils (impedance bridge) in
the reader developed by Magnasense.
Magnetic labels bound to the test line
unbalance the impedance bridge, leading to a
change in the output voltage (V). The reader
developed by MagnaBioSciences is based on
a different approach, in which the lateral fl ow
device is located in a uniform magnetic fi eld
above an array of coils.
porated into a lateral fl ow device reader based on electromagnetic induction, but
it also has the potential to improve the sensitivity of Hall, GMR, and other sensors.
Diagnostic Biosensors (Minneapolis, USA; www.diagnosticbiosensors.com) is cur-
rently developing arrays of GMR sensors for use with lateral fl ow and microfl uidic
devices. One problem with GMR as a means of interrogating lateral fl ow strips is
that the sensitivity to the presence of magnetic particles decreases according to
