Biomedical Engineering Reference
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(a)
Strand-displacement probe
hv
hv
FL signal
Quenched
(b)
Molecular beacon
hv
hv
FL signal
Quenched
(c)
Binary FRET probe
FRET signal
hv
hv
FL signal
(d)
FIT probe
FL signal
hv
hv
(e)
Catalytic binary probes
AQ3
fIgure 13.7
Optical antisense turn-on probes. To circumvent unwanted background signal
from unbound probe, a number of clever systems labeled (a)-(e) have been developed that
result in a large increase in fluorescence signal upon hybridizing to the target RNA.
a bio-orthogonal reaction in water, at pH 7 and at 37°c. Another approach has been
to use the RNA itself as a catalyst to bring together two components that react stoi-
chiometrically by a bio-orthogonal reaction to activate fluorescence as first shown
using a Staudinger reaction [102] and then dissociate, thereby allowing for turnover.
Since then, a number of catalytic Staudinger reaction-based turn-on systems for
detecting nucleic acids have been developed, some of which have been shown to also
work
in vivo
[103-105].
13.4.1
antisense Imaging agent delivery
The problem with the individual antisense imaging probes for
in vivo
applications in
animals is that their pharmacokinetics depend on their structure, with unmodified
nucleic acids being rapidly degraded, while some modified nucleic acids are rapidly
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