13 Some Frontier Technologies for Aptamers in Medical Applications
389
As shown in Fig. 13.8, SOMAmer is the aptamer which includes a biotinylated photocleavable linker and fluorescent label at the 5
end and can bind protein or biomarker
molecules specifically (a). Bound protein-SOMAmer complexes can be captured
thereafter onto the streptavidin-coated beads while unbound proteins are washed
away (b). Bound proteins are tagged with biotin for successive experiments (c). The
linker is cleaved by UV light and protein-SOMAmer complexes are liberated into the
solution (d). protein-SOMAmer complexes are captured onto the streptavidin-coated
beads (e). The complexes are subjected to denaturation with the release of SOMAmer
from associated protein (f). Hybridization of SOMAmers with their complementary
probes immobilized onto the microarray biochip, fluorescence intensity is measured
and normalized, and is proportional to the quantity of specific protein or biomarker
in the original sample (g). Based on SomaScan
TM platform, the utility of aptamer
microarray biochip in profiling the protein repertoire of cancer exosomes was well
demonstrated [13].
As shown in Fig. 13.5b, c, d, f, we developed as well an aptamer microarray
biochip for affinity characterization of 16 aptamer candidates incubating with SynOP
on an aldehyde-coated glass slide substrate, and normalized fluorescence intensity
difference values (FIDs) were measured to find practical aptamers toward SynOP for
class-specific binding traits successfully.
13.3.2 Aptamer Microfluidic Biochip
Largely different from that of aptamer microarray biochip, the principle of aptamer
microfluidic biochip as a miniaturized analytical device or point-of-care facility was
based on a “Micro Total Analysis System” (µTAS) or “Lab on a Chip” (LOC)
scheme merging analytical merits of both microfluidics and aptamers in the field of
medical science and research. Compared with aptamer microarray biochip, aptamer
microfluidic biochip is more integrative and capable of fulfilling various medical
assignments.
To fabricate an aptamer microfluidic biochip, target-specific aptamer needs to
be firstly immobilized by non-covalent assembling or chemical covalent conjugation onto the surface of the microchannels or microspheres in polydimethylsiloxane
(PDMS) or glass microchips. As shown in Fig. 13.9, a “Y” type aptamer microfluidic biochip was developed in the author’s lab for the determination of some tetracycline antibiotics in human serum (unpublished data). Polystyrene microspheres
injected and checked at the fluidic slit d with extra microspheres flushed out through
outlet b were firstly incubated and coated with highly selective tetracycline aptamer
via the well-known carbodiimide crosslink chemistry, then tetracycline antibiotics
in human serum and horseradish peroxidase (HRP) labeled tetracycline antibiotics
were injected simultaneously through inlet a into the microchannel to compete for
the limited aptamer immobilized onto the surface of the microspheres, quantitative
measurement could be facilely done with high sensitivity at parts-per-billion level
389
As shown in Fig. 13.8, SOMAmer is the aptamer which includes a biotinylated photocleavable linker and fluorescent label at the 5
end and can bind protein or biomarker
molecules specifically (a). Bound protein-SOMAmer complexes can be captured
thereafter onto the streptavidin-coated beads while unbound proteins are washed
away (b). Bound proteins are tagged with biotin for successive experiments (c). The
linker is cleaved by UV light and protein-SOMAmer complexes are liberated into the
solution (d). protein-SOMAmer complexes are captured onto the streptavidin-coated
beads (e). The complexes are subjected to denaturation with the release of SOMAmer
from associated protein (f). Hybridization of SOMAmers with their complementary
probes immobilized onto the microarray biochip, fluorescence intensity is measured
and normalized, and is proportional to the quantity of specific protein or biomarker
in the original sample (g). Based on SomaScan
TM platform, the utility of aptamer
microarray biochip in profiling the protein repertoire of cancer exosomes was well
demonstrated [13].
As shown in Fig. 13.5b, c, d, f, we developed as well an aptamer microarray
biochip for affinity characterization of 16 aptamer candidates incubating with SynOP
on an aldehyde-coated glass slide substrate, and normalized fluorescence intensity
difference values (FIDs) were measured to find practical aptamers toward SynOP for
class-specific binding traits successfully.
13.3.2 Aptamer Microfluidic Biochip
Largely different from that of aptamer microarray biochip, the principle of aptamer
microfluidic biochip as a miniaturized analytical device or point-of-care facility was
based on a “Micro Total Analysis System” (µTAS) or “Lab on a Chip” (LOC)
scheme merging analytical merits of both microfluidics and aptamers in the field of
medical science and research. Compared with aptamer microarray biochip, aptamer
microfluidic biochip is more integrative and capable of fulfilling various medical
assignments.
To fabricate an aptamer microfluidic biochip, target-specific aptamer needs to
be firstly immobilized by non-covalent assembling or chemical covalent conjugation onto the surface of the microchannels or microspheres in polydimethylsiloxane
(PDMS) or glass microchips. As shown in Fig. 13.9, a “Y” type aptamer microfluidic biochip was developed in the author’s lab for the determination of some tetracycline antibiotics in human serum (unpublished data). Polystyrene microspheres
injected and checked at the fluidic slit d with extra microspheres flushed out through
outlet b were firstly incubated and coated with highly selective tetracycline aptamer
via the well-known carbodiimide crosslink chemistry, then tetracycline antibiotics
in human serum and horseradish peroxidase (HRP) labeled tetracycline antibiotics
were injected simultaneously through inlet a into the microchannel to compete for
the limited aptamer immobilized onto the surface of the microspheres, quantitative
measurement could be facilely done with high sensitivity at parts-per-billion level