8 Aptamers for the Diagnosis of Infectious Diseases
217
8.3.1.1 Hepatitis B Diagnosis
Hepatitis B is an infectious disease caused by the hepatitis B virus (HBV) that
affects the liver. As it is reported, a quarter of HBV-infected children will develop
into primary liver cancer or cirrhosis in adulthood, and chronic hepatitis B virus
infection (CHB) is a major public health issue worldwide. Hepatitis B e antigen
(HBeAg) seroconversion is used as an indicator of virological response to hepatitis
B diagnosis. Huang et al. [58] developed a fluorescence-based aptasensor, which had
high sensitivity and specificity for HBeAg detection, with a LOD of 26.5 nM. Later,
the fluorescence system was applied in HBeAg positive and negative bloodserum
(p < 0.05). Particularly, the assay can be completed in 2 min.
Similar to GO, layered molybdenum disulfide (MoS 2 ) also possesses high fluorescence quenching ability and distinct affinity toward single-stranded DNA (ssDNA)
versus double-stranded (dsDNA) and folded DNA. Based on the properties, Qu et al.
[54] reported an MoS 2 nanosheets-based fluorescent aptasensor for HBV determination (Fig. 8.4a). MoS 2 nanosheets will aggregate in the presence of sodium acetate,
and the quenching effect of MoS 2 on silver nanoclusters (AgNCs) is concomitantly
hidden. However, HBV ssDNA aptamer can be easily adsorbed onto the surface
of MoS 2 , producing the fluorescent quenching of AgNCs. Subsequently, the target,
HBV can specifically bind to its aptamer to form dsDNA or folded state, resulting
in the fluorescence recovery. In the aptasensor, the HBV DNA can be detected in
the linear range of 5–30 nM. This method may act as a universal platform for HBV
detection, but the cost will be relatively high for the usage of AgNCs.
DNA nanostructures are effective intermediates for immobilizing biomolecules
because of their high level of controllability and flexibility. Wang et al. [55] reported
the immobilization of HBsAg-binding aptamers with a DNA tetrahedron structure
on agarose via the interaction between streptavidin and biotin. The formation effect
of immobilization was confirmed by electrophoresis and confocal. HBsAg, hepatitis
B virus surface antigens can be removed by immobilization. The result showed
that the average adsorption efficiencies of antibody, aptamer and DNA tetrahedronlinked immobilization for HBsAg were 1–90%, 40–96% and 50–99%, respectively.
Although the adsorption ratio was dependent on the initial concentration of HBsAg,
there was a markedly higher adsorption in DNA tetrahedron-linked immobilization
when the initial concentration was over 200 U/mL (Fig. 8.4b). The assay may provide
a novel option for HBV therapy.
8.3.1.2 Hepatitis C Diagnosis
Hepatitis C is another typical viral hepatitis infected by hepatitis C virus (HCV),
one of the major causes of progressive liver disease. HCV is a single positive-strand
RNA virus encoding a single long polyprotein which is processed into three structural
proteins (core, E1 and E2), ion channel (p7) and six non-structural proteins (NS2,
NS3, NS4A, NS4B, NS5A and NS5B) by cellular and viral enzymes [59]. Interferon
alpha (IFN-a)-based therapy is the current treatment for HC, but unfortunately, many
217
8.3.1.1 Hepatitis B Diagnosis
Hepatitis B is an infectious disease caused by the hepatitis B virus (HBV) that
affects the liver. As it is reported, a quarter of HBV-infected children will develop
into primary liver cancer or cirrhosis in adulthood, and chronic hepatitis B virus
infection (CHB) is a major public health issue worldwide. Hepatitis B e antigen
(HBeAg) seroconversion is used as an indicator of virological response to hepatitis
B diagnosis. Huang et al. [58] developed a fluorescence-based aptasensor, which had
high sensitivity and specificity for HBeAg detection, with a LOD of 26.5 nM. Later,
the fluorescence system was applied in HBeAg positive and negative bloodserum
(p < 0.05). Particularly, the assay can be completed in 2 min.
Similar to GO, layered molybdenum disulfide (MoS 2 ) also possesses high fluorescence quenching ability and distinct affinity toward single-stranded DNA (ssDNA)
versus double-stranded (dsDNA) and folded DNA. Based on the properties, Qu et al.
[54] reported an MoS 2 nanosheets-based fluorescent aptasensor for HBV determination (Fig. 8.4a). MoS 2 nanosheets will aggregate in the presence of sodium acetate,
and the quenching effect of MoS 2 on silver nanoclusters (AgNCs) is concomitantly
hidden. However, HBV ssDNA aptamer can be easily adsorbed onto the surface
of MoS 2 , producing the fluorescent quenching of AgNCs. Subsequently, the target,
HBV can specifically bind to its aptamer to form dsDNA or folded state, resulting
in the fluorescence recovery. In the aptasensor, the HBV DNA can be detected in
the linear range of 5–30 nM. This method may act as a universal platform for HBV
detection, but the cost will be relatively high for the usage of AgNCs.
DNA nanostructures are effective intermediates for immobilizing biomolecules
because of their high level of controllability and flexibility. Wang et al. [55] reported
the immobilization of HBsAg-binding aptamers with a DNA tetrahedron structure
on agarose via the interaction between streptavidin and biotin. The formation effect
of immobilization was confirmed by electrophoresis and confocal. HBsAg, hepatitis
B virus surface antigens can be removed by immobilization. The result showed
that the average adsorption efficiencies of antibody, aptamer and DNA tetrahedronlinked immobilization for HBsAg were 1–90%, 40–96% and 50–99%, respectively.
Although the adsorption ratio was dependent on the initial concentration of HBsAg,
there was a markedly higher adsorption in DNA tetrahedron-linked immobilization
when the initial concentration was over 200 U/mL (Fig. 8.4b). The assay may provide
a novel option for HBV therapy.
8.3.1.2 Hepatitis C Diagnosis
Hepatitis C is another typical viral hepatitis infected by hepatitis C virus (HCV),
one of the major causes of progressive liver disease. HCV is a single positive-strand
RNA virus encoding a single long polyprotein which is processed into three structural
proteins (core, E1 and E2), ion channel (p7) and six non-structural proteins (NS2,
NS3, NS4A, NS4B, NS5A and NS5B) by cellular and viral enzymes [59]. Interferon
alpha (IFN-a)-based therapy is the current treatment for HC, but unfortunately, many