8 Aptamers for the Diagnosis of Infectious Diseases
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for typical infectious diseases, such as cholera, tuberculosis, anthrax, malaria, viral
hepatitis and AIDS. We also present the roles of aptamers serving as field-deployable
assays for diseases profiling, as well as imaging probes for cellular monitoring.
We have drawn on key examples on aptamer-based diagnosis for typical infectious
diseases, providing perspectives on the aptamer-based diagnosis.
8.2 Bacterial Infectious Diseases
8.2.1 Cholera
Cholera, originating from South Asia in 1961, is a clinical-epidemiologic syndrome
caused by Vibrio cholera (V. cholera) [22]. Clinical disease characters are hypovolemic shock, acidosis, diarrhea and even death if treatment is not initiated in a timely
manner. Cholera can be transmitted to humans via ingestion of contaminated water
or food, as well as from person to person contact via the fecal-oral route [23]. In
2019, the World Health Organization (WHO) reported that each year there were 1.3
million to 4.0 million cases, and 21,000 to 143,000 deaths of cholera worldwide.
V. cholera serogroups of epidemic cholera are recognized as O1 and O139,
of which serogroup O139 Bengal has emerged as a human pathogen since 1992
[24]. Humans are known as the only natural vertebrate host for V. cholera. The
pathogenicity of the strain is not to invade cells, but to secrete cholera toxin (CT)
which is a protein comprising one A subunit and five B subunits. Each B subunit
is related to gene edition, so cholera toxin B (CT-B) is the main target in cholera
diagnosis [25].
The Centers for Disease Control (CDC) recommends the gold standard for the
laboratory diagnosis of cholera which is the isolation and identification of V. cholerae
serogroup O1 or O139 by the culture of a stool specimen. Culture and PCR are
powerful tools for V. cholerae identification.
The Crystal
® VC dipstick is another choice for rapid cholera test. Most of the
methods, however, require specialized and expensive equipment. Recently, the developed aptamers are proposed against CT, and the frequently used DNA aptamer for CT
detection is named CT916. The secondary structure of CT916 is showed in Fig. 8.1a.
In 2002, Kiel et al. [27] pioneered to use SELEX to develop aptamers for cholera
whole toxin identification. Aptamer affinity was sifted by conjugating the biotoxins
to tosyl-activated magnetic beads. Two assays of aptamer-based CT detection—an
electrochemiluminescence method using an aptamer-magnetic bead toxin capture
technique involving Ru(bpy)
32+ -labeled toxins and a colorimetric enzyme-linked
microplate method were compared. To improve the sensitivity of the method, Fischer
et al. [28] proposed a direct enzyme-linked aptamer assay (ELAA) to detect CT in
buffer and tap water. Biotin-modified CT916 was coupled to magnetic beads to
serve as the capture element. The test could be completed within 0.5 h. The limits
of detection (LOD) were 2.1 ng/mL in buffer and 2.4 ng/mL in tap water, with a
209
for typical infectious diseases, such as cholera, tuberculosis, anthrax, malaria, viral
hepatitis and AIDS. We also present the roles of aptamers serving as field-deployable
assays for diseases profiling, as well as imaging probes for cellular monitoring.
We have drawn on key examples on aptamer-based diagnosis for typical infectious
diseases, providing perspectives on the aptamer-based diagnosis.
8.2 Bacterial Infectious Diseases
8.2.1 Cholera
Cholera, originating from South Asia in 1961, is a clinical-epidemiologic syndrome
caused by Vibrio cholera (V. cholera) [22]. Clinical disease characters are hypovolemic shock, acidosis, diarrhea and even death if treatment is not initiated in a timely
manner. Cholera can be transmitted to humans via ingestion of contaminated water
or food, as well as from person to person contact via the fecal-oral route [23]. In
2019, the World Health Organization (WHO) reported that each year there were 1.3
million to 4.0 million cases, and 21,000 to 143,000 deaths of cholera worldwide.
V. cholera serogroups of epidemic cholera are recognized as O1 and O139,
of which serogroup O139 Bengal has emerged as a human pathogen since 1992
[24]. Humans are known as the only natural vertebrate host for V. cholera. The
pathogenicity of the strain is not to invade cells, but to secrete cholera toxin (CT)
which is a protein comprising one A subunit and five B subunits. Each B subunit
is related to gene edition, so cholera toxin B (CT-B) is the main target in cholera
diagnosis [25].
The Centers for Disease Control (CDC) recommends the gold standard for the
laboratory diagnosis of cholera which is the isolation and identification of V. cholerae
serogroup O1 or O139 by the culture of a stool specimen. Culture and PCR are
powerful tools for V. cholerae identification.
The Crystal
® VC dipstick is another choice for rapid cholera test. Most of the
methods, however, require specialized and expensive equipment. Recently, the developed aptamers are proposed against CT, and the frequently used DNA aptamer for CT
detection is named CT916. The secondary structure of CT916 is showed in Fig. 8.1a.
In 2002, Kiel et al. [27] pioneered to use SELEX to develop aptamers for cholera
whole toxin identification. Aptamer affinity was sifted by conjugating the biotoxins
to tosyl-activated magnetic beads. Two assays of aptamer-based CT detection—an
electrochemiluminescence method using an aptamer-magnetic bead toxin capture
technique involving Ru(bpy)
32+ -labeled toxins and a colorimetric enzyme-linked
microplate method were compared. To improve the sensitivity of the method, Fischer
et al. [28] proposed a direct enzyme-linked aptamer assay (ELAA) to detect CT in
buffer and tap water. Biotin-modified CT916 was coupled to magnetic beads to
serve as the capture element. The test could be completed within 0.5 h. The limits
of detection (LOD) were 2.1 ng/mL in buffer and 2.4 ng/mL in tap water, with a