14 Perspectives of Aptamers for Medical Applications
417
In order to enhance the detection efficiency of cortisol in a biological fluid, An
immobilization-free electrochemical sensor was developed by Sanghavi et al. [58].
The aptasensor has independent recognition of the aptamer and target signal, and
thus, could be optimized separately for better specificity. Cortisol competes with
triamcinolone, similar congeners of cortisol, which is bound to the cortisol aptamer
conjugated to gold nanoparticles when cortisol is absent. The cortisol level is detected
as per the signal from the displaced triamcinolone using square wave voltammetry
at patterned graphene-modified electrodes in a microfluidic or nanoslit device. The
aptamer assay displayed rapid binding kinetics with cortisol, and the acceptable
signal linearity range is 10 μg/mL–30 pg/mL. It presents a similar sensitivity and
accuracy compared with ELISA and radioimmunoassay. However, it can be fulfilled
with little volume sample (<1 μL) and much shorter assay time (2.5 min for our
assay compared to hours for ELISA or radioimmunoassay).
Zhang and Gopinath [54] established a cortisol aptamer-conjugated gold nanorod
sensor to quantify cortisol levels in pregnant women. The variation of cortisol level
in a pregnant woman may be the warning of the complications of hypoglycemia and
hypertension. This aptasensor can be quantified to detect the cortisol in serum with
a limitation of 0.01 ng/mL, and the linearity ranged from 0.01 to 0.1 ng/mL. Despite
that, this cortisol aptamer presented a super specificity to discriminate against closely
related cortisol analogs, including norepinephrine and progesterone.
14.3.1.4 Cardiovascular Disease
The acute coronary syndrome (ACS) represents the most common cause of emergency hospital admission. Early ACS diagnosis can reduce complications and risk
of recurrence, total enzyme activity of aspartate aminotransferase (AST), lactate
dehydrogenase (LDH), and creatine kinase (CK) with cardiac troponins being the
main accepted biomarkers for diagnosing the myocardial injury and acute myocardial
infarction (AMI).
Cardiac troponin I (cTnI) is regarded as the new “gold standard” for CVDs diagnosis by the European Society of Cardiology (Sheng et al. 2017). The concentration
of cTnI would provide the basis for the doctor to judge the size of the infarction area.
Negahdary et al. [59] designed a troponin I (TnI) aptamer-based biosensor with a
detection range of 0.03–2.0 ng mL
−1 without using any label, pre-concentration, or
amplification steps. The limit of detection was 10 pg mL
−1 with higher specificity.
The further validation in human specimens was also represented 100% and 81%,
diagnostic sensitivity and specificity, respectively.
Qiao et al. [60] constructed a novel label-free electrochemical aptasensor based on
MoS2 nanosheet to detect cTnI, the linear range for cTnI detection was more sensitive
from 10 pM to 1.0 μM with a lower detection limit of 0.95 pM. This aptamer was
also validated its super specificity in human serum.
417
In order to enhance the detection efficiency of cortisol in a biological fluid, An
immobilization-free electrochemical sensor was developed by Sanghavi et al. [58].
The aptasensor has independent recognition of the aptamer and target signal, and
thus, could be optimized separately for better specificity. Cortisol competes with
triamcinolone, similar congeners of cortisol, which is bound to the cortisol aptamer
conjugated to gold nanoparticles when cortisol is absent. The cortisol level is detected
as per the signal from the displaced triamcinolone using square wave voltammetry
at patterned graphene-modified electrodes in a microfluidic or nanoslit device. The
aptamer assay displayed rapid binding kinetics with cortisol, and the acceptable
signal linearity range is 10 μg/mL–30 pg/mL. It presents a similar sensitivity and
accuracy compared with ELISA and radioimmunoassay. However, it can be fulfilled
with little volume sample (<1 μL) and much shorter assay time (2.5 min for our
assay compared to hours for ELISA or radioimmunoassay).
Zhang and Gopinath [54] established a cortisol aptamer-conjugated gold nanorod
sensor to quantify cortisol levels in pregnant women. The variation of cortisol level
in a pregnant woman may be the warning of the complications of hypoglycemia and
hypertension. This aptasensor can be quantified to detect the cortisol in serum with
a limitation of 0.01 ng/mL, and the linearity ranged from 0.01 to 0.1 ng/mL. Despite
that, this cortisol aptamer presented a super specificity to discriminate against closely
related cortisol analogs, including norepinephrine and progesterone.
14.3.1.4 Cardiovascular Disease
The acute coronary syndrome (ACS) represents the most common cause of emergency hospital admission. Early ACS diagnosis can reduce complications and risk
of recurrence, total enzyme activity of aspartate aminotransferase (AST), lactate
dehydrogenase (LDH), and creatine kinase (CK) with cardiac troponins being the
main accepted biomarkers for diagnosing the myocardial injury and acute myocardial
infarction (AMI).
Cardiac troponin I (cTnI) is regarded as the new “gold standard” for CVDs diagnosis by the European Society of Cardiology (Sheng et al. 2017). The concentration
of cTnI would provide the basis for the doctor to judge the size of the infarction area.
Negahdary et al. [59] designed a troponin I (TnI) aptamer-based biosensor with a
detection range of 0.03–2.0 ng mL
−1 without using any label, pre-concentration, or
amplification steps. The limit of detection was 10 pg mL
−1 with higher specificity.
The further validation in human specimens was also represented 100% and 81%,
diagnostic sensitivity and specificity, respectively.
Qiao et al. [60] constructed a novel label-free electrochemical aptasensor based on
MoS2 nanosheet to detect cTnI, the linear range for cTnI detection was more sensitive
from 10 pM to 1.0 μM with a lower detection limit of 0.95 pM. This aptamer was
also validated its super specificity in human serum.