11 Hormone Aptamers in Endocrine-Related Diseases
337
such as vancomycin [83], tobramycin [82], doxorubicin [73]. However, there are few
aptasensors to date for real-time monitoring of hormones, and only one aptasensor
aimed at real-time detection of insulin has been developed.
11.3.2.1 Aptasensor for Real-Time Detection of Insulin
In 2017, Hao [84] has made real-time monitoring of insulin possible by using a
graphene field-effect transistor aptameric nanosensor. The sequence of the insulinspecific aptamer IGA3 is 5
-NH2-GGT GGT GGG GGGGGT TGG TAG GGTGTC
TTC-3
.The nanosensor is based on a graphene field-effect transistor (GFET), whose
conducting channel is functionalized with a guanine-rich IGA aptamer. Due to the
high mobility and large surface-to-volume ratio of graphene, the GFET is sensible
to the changes in the charge distribution on and in the immediate vicinity of the
graphene surface. After binding to insulin, the negatively charged aptamer folds into
a tight and stable antiparallel or parallel G-quadrustr and conformation, leading to
a carrier density change of graphene, which changes the conductivity accordingly.
Changes in electrical conductivity are then measured via square wave voltammetry
to enable real-time monitoring of insulin levels, the sensitivity of this aptasensor is
superior to that of other methods, for the LOD is estimated to be 35 pM.
11.3.3 Application of Aptamer in Targeted Therapy
Aptamers are used in treatment similar to monoclonal antibodies. However, unlike
traditional methods of producing monoclonal antibodies, in vitro selection of
oligonucleotides does not require any organism, and the chemistry, selection conditions, and targets are all operated in vitro which may be difficult or impossible
if organic matrices matter is involved. Besides, aptamers as therapeutics are also
different from other oligonucleotide therapeutics. In the case of antisense oligonucleotides or siRNA, therapeutic targets are intracellular, while aptamers can be
developed exclusively for intracellular, extracellular, or cell-surface targets. Targeted
proteins in the latter two classes reduce the need for therapeutic agents to cross cell
membranes. In addition, like monoclonal antibodies, aptamers could theoretically be
used in any disease that requires extracellular blocking of protein-protein interactions.
Most therapeutically utilizable aptamers tend to inhibit protein–protein interactions,
such as receptor-ligand interactions, thus acting as antagonists.
11.3.3.1 Application of Aptamer in Breast Cancer Treatment
As aforementioned, breast cancer is one of the most common malignant tumors in
women. It is associated with genetic and environmental factors. Women between 40
and 60 years old, before and after menopause have a higher risk of getting affected
337
such as vancomycin [83], tobramycin [82], doxorubicin [73]. However, there are few
aptasensors to date for real-time monitoring of hormones, and only one aptasensor
aimed at real-time detection of insulin has been developed.
11.3.2.1 Aptasensor for Real-Time Detection of Insulin
In 2017, Hao [84] has made real-time monitoring of insulin possible by using a
graphene field-effect transistor aptameric nanosensor. The sequence of the insulinspecific aptamer IGA3 is 5
-NH2-GGT GGT GGG GGGGGT TGG TAG GGTGTC
TTC-3
.The nanosensor is based on a graphene field-effect transistor (GFET), whose
conducting channel is functionalized with a guanine-rich IGA aptamer. Due to the
high mobility and large surface-to-volume ratio of graphene, the GFET is sensible
to the changes in the charge distribution on and in the immediate vicinity of the
graphene surface. After binding to insulin, the negatively charged aptamer folds into
a tight and stable antiparallel or parallel G-quadrustr and conformation, leading to
a carrier density change of graphene, which changes the conductivity accordingly.
Changes in electrical conductivity are then measured via square wave voltammetry
to enable real-time monitoring of insulin levels, the sensitivity of this aptasensor is
superior to that of other methods, for the LOD is estimated to be 35 pM.
11.3.3 Application of Aptamer in Targeted Therapy
Aptamers are used in treatment similar to monoclonal antibodies. However, unlike
traditional methods of producing monoclonal antibodies, in vitro selection of
oligonucleotides does not require any organism, and the chemistry, selection conditions, and targets are all operated in vitro which may be difficult or impossible
if organic matrices matter is involved. Besides, aptamers as therapeutics are also
different from other oligonucleotide therapeutics. In the case of antisense oligonucleotides or siRNA, therapeutic targets are intracellular, while aptamers can be
developed exclusively for intracellular, extracellular, or cell-surface targets. Targeted
proteins in the latter two classes reduce the need for therapeutic agents to cross cell
membranes. In addition, like monoclonal antibodies, aptamers could theoretically be
used in any disease that requires extracellular blocking of protein-protein interactions.
Most therapeutically utilizable aptamers tend to inhibit protein–protein interactions,
such as receptor-ligand interactions, thus acting as antagonists.
11.3.3.1 Application of Aptamer in Breast Cancer Treatment
As aforementioned, breast cancer is one of the most common malignant tumors in
women. It is associated with genetic and environmental factors. Women between 40
and 60 years old, before and after menopause have a higher risk of getting affected