8 Aptamers for the Diagnosis of Infectious Diseases
213
(PEDOT) doped with carbon nanotubes (CNTs). The signal was monitored by differential pulse voltammetry in the presence of [Fe(CN) 6 ]
3-/4- as a redox probe. The
aptasensor presented some novel features, such as long-term stability, reproducibility
and cost-effectiveness, leading to a new prospect for the rapid diagnosis of TB.
Taghdisi et al. [34] developed a GO-ATTO647N-labeled aptamer-based fluorescence assay for M. tuberculosis antigenic protein FbpA detection. In the absence of
target molecule (FbpA), ATTO647N-Apt22 will bind onto the GO, resulting in the
fluorescence quenching of ATTO. While when target (FbpA) is present, the aptamer
interacts with the target and then forms FbpA/Apt 22 complex so that it cannot bind
onto the GO, which holds accountable for a strong fluorescence intensity (Fig. 8.2d).
The assay applies to the rapid target detection with a high signal-to-noise ratio (SNR)
(Table 8.2).
8.2.3 Anthrax
Anthrax is an epizootic disease caused by Bacillus anthraces (B. anthracite), a large,
gram-positive and aerobic spore-forming bacillus. It primarily affects cattle, but it
can also affect humans exposed to infected animals or associated products [39]. B.
anthracite is encoded on two plasmids: pXO1 and pXO2. pXO1 carries the genes
encoding the anthrax toxins: protective antigen (pagA, PA), lethal factor (lef , LF) and
edema factor (cya, EF) [40]. The proteins are non-toxic individually until combining
with PA to form edema toxin (EdTx) and lethal toxin (LeTx), both of which cause cell
death [41]. Toxins secreted by B. anthracis may impair the host immune response,
allowing for fast bacterial proliferation, sepsis and causing host death within hours
of symptom development.
Among the three toxins secreted by B. anthracis, LF has been regarded as a
biomarker for detecting bacterial infection and an effective target to neutralize
toxicity [42]. Kim et al. [43] studied the inhibition effect of ssDNA aptamers on
anthrax LF. In the study, they developed ssDNA aptamers against LF and designed
an aptamer-based ELISA method to visualize the presence of LF. The aptamer with
high affinity to LF was an effective toxin inhibitor with an IC50 value of 15 ± 1.5 µM
and approximately 85% cell viability. The aptamer provided a potential clue for a
sensitive diagnostic device of B. anthraces.
The PA of B. anthracite is the most critical virulence factor in secreted protein,
so PA is often used as a target in detecting bacterial infection [40]. Yoon group
[44] adopted SELEX to select single-strand DNA aptamers binding to PA. After
selection, they attempted to visualize the detection of PA using an aptamer-based
ELISA, and two aptamers, BH-2 and BH-4, were proposed with a low nanomolar
range K d values. To develop ideal aptamer-based platforms for anthrax detection, it
is necessary to identify and select aptamers that can simply bind to the biomarker
of anthrax. In 2012, Bruno et al. [45] tried to identify DNA aptamer beacons from
a sequence library which can simply bind and detect Bacillus pathogens or other
Bacillus spore species. The two aptamers were selected and named BAS-6F and
213
(PEDOT) doped with carbon nanotubes (CNTs). The signal was monitored by differential pulse voltammetry in the presence of [Fe(CN) 6 ]
3-/4- as a redox probe. The
aptasensor presented some novel features, such as long-term stability, reproducibility
and cost-effectiveness, leading to a new prospect for the rapid diagnosis of TB.
Taghdisi et al. [34] developed a GO-ATTO647N-labeled aptamer-based fluorescence assay for M. tuberculosis antigenic protein FbpA detection. In the absence of
target molecule (FbpA), ATTO647N-Apt22 will bind onto the GO, resulting in the
fluorescence quenching of ATTO. While when target (FbpA) is present, the aptamer
interacts with the target and then forms FbpA/Apt 22 complex so that it cannot bind
onto the GO, which holds accountable for a strong fluorescence intensity (Fig. 8.2d).
The assay applies to the rapid target detection with a high signal-to-noise ratio (SNR)
(Table 8.2).
8.2.3 Anthrax
Anthrax is an epizootic disease caused by Bacillus anthraces (B. anthracite), a large,
gram-positive and aerobic spore-forming bacillus. It primarily affects cattle, but it
can also affect humans exposed to infected animals or associated products [39]. B.
anthracite is encoded on two plasmids: pXO1 and pXO2. pXO1 carries the genes
encoding the anthrax toxins: protective antigen (pagA, PA), lethal factor (lef , LF) and
edema factor (cya, EF) [40]. The proteins are non-toxic individually until combining
with PA to form edema toxin (EdTx) and lethal toxin (LeTx), both of which cause cell
death [41]. Toxins secreted by B. anthracis may impair the host immune response,
allowing for fast bacterial proliferation, sepsis and causing host death within hours
of symptom development.
Among the three toxins secreted by B. anthracis, LF has been regarded as a
biomarker for detecting bacterial infection and an effective target to neutralize
toxicity [42]. Kim et al. [43] studied the inhibition effect of ssDNA aptamers on
anthrax LF. In the study, they developed ssDNA aptamers against LF and designed
an aptamer-based ELISA method to visualize the presence of LF. The aptamer with
high affinity to LF was an effective toxin inhibitor with an IC50 value of 15 ± 1.5 µM
and approximately 85% cell viability. The aptamer provided a potential clue for a
sensitive diagnostic device of B. anthraces.
The PA of B. anthracite is the most critical virulence factor in secreted protein,
so PA is often used as a target in detecting bacterial infection [40]. Yoon group
[44] adopted SELEX to select single-strand DNA aptamers binding to PA. After
selection, they attempted to visualize the detection of PA using an aptamer-based
ELISA, and two aptamers, BH-2 and BH-4, were proposed with a low nanomolar
range K d values. To develop ideal aptamer-based platforms for anthrax detection, it
is necessary to identify and select aptamers that can simply bind to the biomarker
of anthrax. In 2012, Bruno et al. [45] tried to identify DNA aptamer beacons from
a sequence library which can simply bind and detect Bacillus pathogens or other
Bacillus spore species. The two aptamers were selected and named BAS-6F and