62
G. Murtaza et al.
membrane, the barrel was opened to release Fab antibody fragments that bind to
human CD 33 and CDw328 to inhibit growth of leukemia cells. The logic-gated
locks with specific recognition were designed to enhance targeting specificity [55].
Koirala et al. used 2D and 3D DNA origami nanostructures to expand single
molecule platforms in a new mechanochemical sensing strategy. As a proof of
concept, six sensing probes were added to a 7-tile DNA origami nanoassembly,
where the binding of a target molecule to any of these probes led to mechanochemical rearrangement of the origami, which was monitored in real time by optical
tweezers. Using these platforms, 10 pM platelet-derived growth factor (PDGF) was
detected within 10 min, showing the multiplex sensing of the PDGF and a target
DNA in the same solution [56]. With a 24-helix bundle, a DNA origami structure
was designed with two times 11 protruding arms on opposite sides to attach to
the gold surface and to arrange thrombin-specific aptamers with specific density and
distance (27 nm) from the SPR surface. The origami-based technology demonstrated
potential to perform reproducible, label-free detection of thrombin within a range of
0–248 nM, and also showed important novel features. First, a better performance was
observed for both DNA structures. Second, the functionalization of DNA origami
on the surface of the SPR sensing chip resulted in a wider linear detection range
compared with functionalization with tetrahedrons [57].
A fluorescent aptasensor was presented for the determination of Carcinoembryonic antigen (CEA) as a tumor marker associated with breast, gastric and
colorectal cancers. In this regard, a fluorescent aptasensor was used for determination
of CEA, using three-way junction pocket and 5, 6, 7-trimethyl-1, 8-naphthyridin2-amine (ATMND) as a fluorescent probe. Upon trapping of ATMND within the
three-way junction structures especially with GC nucleotides repeats, ATMND fluorescence is quenched. In the absence of CEA, three-way junction structure consisting
of Apt, CS1 and CS2 is formed and ATMND is trapped in this structure. Therefore,
a weak fluorescence response is detected. With the target, the Apt-CEA complex is
formed, leading to the absence of three way junction construction. So, following the
addition of ATMND, a powerful fluorescence signal can be recorded. The fluorescent
aptasensor demonstrated LOD of 1.5 pg.mL
−1 with a broad linear range from 4.5
pg.mL
−1 to 30 ng.mL
−1 of CEA [58].
Sun et al. designed a competitive and label-free electrochemical aptasensor
for determination of HepG2 tumor cells by using DNA origami technology. In
the first step, the DNA nanotetrahedron (NTH) containing the TLS11a aptamer
probe with a high affinity for liver cancer HepG2 cells is fixed on the surface
of a screen-printed gold electrode (SPGE). Then, nanoprobes (nanoprobe1 and
nanoprobe2) are constructed by Pd–Pt nanocages labeled with horseradish peroxidase(HRP), hemin/G-quadruplex DNAzyme, and two complementary DNA(cDNA1
and cDNA2).
Nanoprobes are immobilized with self-assembled nanoprobes on the SPGE
surface through DNA hybridization and form dendritic structure (DS). The high
amount of HRP, Gquadruplex/hemin DNAzyme, and nanocages of the generated
DS nanoprobes will strengthen the electrochemical response and increase the sensor
sensitivity. Once target cells are subjected to the designed system, they bind to the
G. Murtaza et al.
membrane, the barrel was opened to release Fab antibody fragments that bind to
human CD 33 and CDw328 to inhibit growth of leukemia cells. The logic-gated
locks with specific recognition were designed to enhance targeting specificity [55].
Koirala et al. used 2D and 3D DNA origami nanostructures to expand single
molecule platforms in a new mechanochemical sensing strategy. As a proof of
concept, six sensing probes were added to a 7-tile DNA origami nanoassembly,
where the binding of a target molecule to any of these probes led to mechanochemical rearrangement of the origami, which was monitored in real time by optical
tweezers. Using these platforms, 10 pM platelet-derived growth factor (PDGF) was
detected within 10 min, showing the multiplex sensing of the PDGF and a target
DNA in the same solution [56]. With a 24-helix bundle, a DNA origami structure
was designed with two times 11 protruding arms on opposite sides to attach to
the gold surface and to arrange thrombin-specific aptamers with specific density and
distance (27 nm) from the SPR surface. The origami-based technology demonstrated
potential to perform reproducible, label-free detection of thrombin within a range of
0–248 nM, and also showed important novel features. First, a better performance was
observed for both DNA structures. Second, the functionalization of DNA origami
on the surface of the SPR sensing chip resulted in a wider linear detection range
compared with functionalization with tetrahedrons [57].
A fluorescent aptasensor was presented for the determination of Carcinoembryonic antigen (CEA) as a tumor marker associated with breast, gastric and
colorectal cancers. In this regard, a fluorescent aptasensor was used for determination
of CEA, using three-way junction pocket and 5, 6, 7-trimethyl-1, 8-naphthyridin2-amine (ATMND) as a fluorescent probe. Upon trapping of ATMND within the
three-way junction structures especially with GC nucleotides repeats, ATMND fluorescence is quenched. In the absence of CEA, three-way junction structure consisting
of Apt, CS1 and CS2 is formed and ATMND is trapped in this structure. Therefore,
a weak fluorescence response is detected. With the target, the Apt-CEA complex is
formed, leading to the absence of three way junction construction. So, following the
addition of ATMND, a powerful fluorescence signal can be recorded. The fluorescent
aptasensor demonstrated LOD of 1.5 pg.mL
−1 with a broad linear range from 4.5
pg.mL
−1 to 30 ng.mL
−1 of CEA [58].
Sun et al. designed a competitive and label-free electrochemical aptasensor
for determination of HepG2 tumor cells by using DNA origami technology. In
the first step, the DNA nanotetrahedron (NTH) containing the TLS11a aptamer
probe with a high affinity for liver cancer HepG2 cells is fixed on the surface
of a screen-printed gold electrode (SPGE). Then, nanoprobes (nanoprobe1 and
nanoprobe2) are constructed by Pd–Pt nanocages labeled with horseradish peroxidase(HRP), hemin/G-quadruplex DNAzyme, and two complementary DNA(cDNA1
and cDNA2).
Nanoprobes are immobilized with self-assembled nanoprobes on the SPGE
surface through DNA hybridization and form dendritic structure (DS). The high
amount of HRP, Gquadruplex/hemin DNAzyme, and nanocages of the generated
DS nanoprobes will strengthen the electrochemical response and increase the sensor
sensitivity. Once target cells are subjected to the designed system, they bind to the