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G. Murtaza et al.
(TPP2), clinics (TPP3), peripheral laboratories (TPP4), and hospitals (TPP5) [3].
To develop highly sensitive and specific assay, the molecular recognition elements
(MREs) with high affinity and specificity are necessary.
Antibodies are the commonly used MREs. However, single-stranded DNA
(ssDNA) or RNA aptamers have attracted much attention as a type of “chemical antibodies” in the last three decades. They have revealed excellent affinity and selectivity
toward a wider range of targets including ions small molecules, peptides, proteins,
whole cells bacteria and viruses [4–6], have several advantages over antibodies: easy
to prepare and modify, cheaper and stable, no batch variations and non-immunogenic
[7]. They behave actively as sensing probes in biomedicine and bioanalysis in the
last 30 years.
Moreover, generation of different aptamers with higher affinities and specificities
pave the way for the complementation with other molecules, such as monoclonal antibodies and siRNA for diagnostic and inhibition processes, a sequential development
in the drug industry. The combination of aptamers and antibodies has demonstrated
the increasing performance, sensitivity improvements with several folds. An integrated approach based on in vivo capture using antibody cocktail and multicolor
fluorescence imaging using aptamer has been developed for high-efficiency capture
of circulating tumor cells (CTCs) and the precise location of the primary tumor [8].
Aptamers and small-interfering RNAs have been used as chimeras for therapy
of brain cancers. Esposito et al. used aptamers as carriers to specifically direct a
STAT3 siRNA to GBM cells in a receptor-dependent manner [9]. With the versatile
functions, aptamers are entering the biosensing field as the increasingly fledged probe
molecules, and are compatible with numerous sensing platforms or biosensor.
3.2 Aptamers as Sensing Probes in POCT
POCTs rely on different biomolecules as probes, such as antibodies, nucleic acids,
aptamers, and enzymes. Antibodies have been the most popular with different POCT
systems, reported over a period of 10 decades, whereas the application of aptamers has
been demonstrated for less than three decades. Although aptamers were discovered
much later than antibodies, they have several benefits over antibodies such as being
cheaper, small size, easier to modify, nonimmunogenic and stable [7, 10]. While
many antibodies are temperature sensitive, they degrade upon contact with surfaces,
aptamers are highly stable and can be stored and transported at ambient temperatures
and can undergo reversible denaturation [11]. Aptamers’ dissociation constants (Kd)
are comparable to antibodies and range from picomolar to nanomolar. They can
distinguish between closely related molecules, a highly desirable feature that assigns
aptamers high degree of specificity [12].
The conventional nucleic acid probes were based on base paring and hybridization
of complementary strands [13], whereas aptamers can undergo change in conformation upon binding to their targets [14]. Based on these features, aptamers found
their place in enzyme-linked immunosorbent assay (ELISA) as capture probes
G. Murtaza et al.
(TPP2), clinics (TPP3), peripheral laboratories (TPP4), and hospitals (TPP5) [3].
To develop highly sensitive and specific assay, the molecular recognition elements
(MREs) with high affinity and specificity are necessary.
Antibodies are the commonly used MREs. However, single-stranded DNA
(ssDNA) or RNA aptamers have attracted much attention as a type of “chemical antibodies” in the last three decades. They have revealed excellent affinity and selectivity
toward a wider range of targets including ions small molecules, peptides, proteins,
whole cells bacteria and viruses [4–6], have several advantages over antibodies: easy
to prepare and modify, cheaper and stable, no batch variations and non-immunogenic
[7]. They behave actively as sensing probes in biomedicine and bioanalysis in the
last 30 years.
Moreover, generation of different aptamers with higher affinities and specificities
pave the way for the complementation with other molecules, such as monoclonal antibodies and siRNA for diagnostic and inhibition processes, a sequential development
in the drug industry. The combination of aptamers and antibodies has demonstrated
the increasing performance, sensitivity improvements with several folds. An integrated approach based on in vivo capture using antibody cocktail and multicolor
fluorescence imaging using aptamer has been developed for high-efficiency capture
of circulating tumor cells (CTCs) and the precise location of the primary tumor [8].
Aptamers and small-interfering RNAs have been used as chimeras for therapy
of brain cancers. Esposito et al. used aptamers as carriers to specifically direct a
STAT3 siRNA to GBM cells in a receptor-dependent manner [9]. With the versatile
functions, aptamers are entering the biosensing field as the increasingly fledged probe
molecules, and are compatible with numerous sensing platforms or biosensor.
3.2 Aptamers as Sensing Probes in POCT
POCTs rely on different biomolecules as probes, such as antibodies, nucleic acids,
aptamers, and enzymes. Antibodies have been the most popular with different POCT
systems, reported over a period of 10 decades, whereas the application of aptamers has
been demonstrated for less than three decades. Although aptamers were discovered
much later than antibodies, they have several benefits over antibodies such as being
cheaper, small size, easier to modify, nonimmunogenic and stable [7, 10]. While
many antibodies are temperature sensitive, they degrade upon contact with surfaces,
aptamers are highly stable and can be stored and transported at ambient temperatures
and can undergo reversible denaturation [11]. Aptamers’ dissociation constants (Kd)
are comparable to antibodies and range from picomolar to nanomolar. They can
distinguish between closely related molecules, a highly desirable feature that assigns
aptamers high degree of specificity [12].
The conventional nucleic acid probes were based on base paring and hybridization
of complementary strands [13], whereas aptamers can undergo change in conformation upon binding to their targets [14]. Based on these features, aptamers found
their place in enzyme-linked immunosorbent assay (ELISA) as capture probes