Biomedical Engineering Reference
In-Depth Information
(a)
(b)
Figure 2.5
(a) An advantage of magnetic
labels is that, subsequent to interrogating a
large sample volume, they can be
concentrated onto a small sensing surface;
(b) By moving the applied magnetic fi eld from
site to site in the direction of the colored
arrows, the magnetic labels can also be
concentrated on each individual sensing spot
in series, but the time required for binding at
each site makes this impractical for
multiplexed detection.
used to focus magnetically labeled nucleic acid sequences onto spin valve sensors
for hybridization with the corresponding probe sequence [23]. One problem with
this approach is that, for maximum sensitivity, it would be necessary to concen-
trate all magnetic labels on one sensing site before moving on to the next, as shown
in Figure 2.5b. In multiplexed detection, where there would be multiple sensing
sites, the total time required would be equal to the number of sensing sites, mul-
tiplied by the time taken to complete the process of concentration and hybridiza-
tion at each individual sensing site. Given that the latter takes at least 30 min, it
can easily be understood that the concentration at individual sensor sites would
not be practical for multiplexed detection.
