correlates to the synthesis of its corresponding receptor interleukin 17RA [24] and
therefore is a promising target. Jo et al. presented a simple impedimetric aptasensor
which is based on the coupling of thiol-modified aptamers on the gold electrode with
deposited gold nanoparticles that are supposed to increase the surface for enhanced
sensitivity. The approach enabled selective target recognition with regard to other
interleukin proteins and a linear range of approx. 10–40 fM [1].
The pro-inflammatory Interleukin 6 is thought to play a role in the occurrence of
major depression as it influences the neurotransmitter metabolism and neural plasticity [25]. Tertiş et al. applied a screen-printed carbon electrode with a film of
polypyrrole and gold nanoparticles. A detection limit of 14 fM and a linear range
from 42 fM to 633 nM cover the essential range [25].
Troponin I gained due to its high specificity for heart damages high relevance as a
biomarker for early detection of, e.g., acute myocardial infarction. Antibody-based
tests, usually ELISA and radioimmunoassay, generally lack thermal stability, require
a complex sample preparation, and are cost-inefficient, albeit being sufficiently
specific and sensitive [26]. Troponin I concentrations below 24.9 pM represent
normal level while high concentrations above 70 pM are indicative for cardiac tissue
damage [27].
In 2015, Jo et al. presented an electrochemical aptasensor that is able to quantify
Troponin I with a linear range of 2 nM to 2 μM in human serum [26]. Wang et al.
introduced a 13-mer peptide aptamer, immobilizing Troponin I on deposited gold
nanoparticles by using the thiol-functionality of the terminal cysteine [28]. This
approach achieved a linear range of 0.7–700 pM. Troponin I detection from clinical
samples showed fair recoveries of 91–105%.
Higher sensitivity was achieved by Akter et al. in 2017 by an antibody-based EIS
sensor [29]. Dendrimers between the electrode and the aptamer enhanced the
performance resulting in even lower detection limits of 11.7 fM and a linear range
of 46 fM to 46 nM. The lowest concentration measured in spiked serum was 460 fM.
Malaria results from an infection caused by parasites belonging to the Plasmodium family. P. falciparum and P. vivax are the main species which are transferred
by the Anopheles mosquito. In 2016, 216 million individuals were affected by
malaria and 445,000 died from it (see WHO malaria report 2017). Recommended
by the WHO as state-of-the-art blood diagnostics are microscopy and rapid diagnostic testing (RDTs) [30]. However, both methods show significant disadvantages:
While microscopy requires time and well-trained experts, RDTs based on antibodies
against Plasmodium lactate dehydrogenase (LDH) show limitations with regard to
costs, sensitivity at low concentrations, specificity, and thermal stability [31]. Nonetheless, since Plasmodium LDH is expressed in the sexual as well as the asexual
stage of the parasite, it is a reliable target for affinity-based sensors.
Lee et al. and Figueroa-Miranda et al. presented impedimetric aptasensors for
Plasmodium LDH determination from patient’s blood and diluted human serum
[31, 32]. In this way, they were able to distinguish between infected and uninfected
blood. A simple design based on co-immobilization of 6-mercapto-1-hexanol and
thiolated aptamer on a gold electrode resulted in a linear detection range of 1–1,000
pM [31]. Figueroa-Miranda et al. reported a linear range of 1 pM to 10 nM of the
50
J.-A. Preuß et al.
therefore is a promising target. Jo et al. presented a simple impedimetric aptasensor
which is based on the coupling of thiol-modified aptamers on the gold electrode with
deposited gold nanoparticles that are supposed to increase the surface for enhanced
sensitivity. The approach enabled selective target recognition with regard to other
interleukin proteins and a linear range of approx. 10–40 fM [1].
The pro-inflammatory Interleukin 6 is thought to play a role in the occurrence of
major depression as it influences the neurotransmitter metabolism and neural plasticity [25]. Tertiş et al. applied a screen-printed carbon electrode with a film of
polypyrrole and gold nanoparticles. A detection limit of 14 fM and a linear range
from 42 fM to 633 nM cover the essential range [25].
Troponin I gained due to its high specificity for heart damages high relevance as a
biomarker for early detection of, e.g., acute myocardial infarction. Antibody-based
tests, usually ELISA and radioimmunoassay, generally lack thermal stability, require
a complex sample preparation, and are cost-inefficient, albeit being sufficiently
specific and sensitive [26]. Troponin I concentrations below 24.9 pM represent
normal level while high concentrations above 70 pM are indicative for cardiac tissue
damage [27].
In 2015, Jo et al. presented an electrochemical aptasensor that is able to quantify
Troponin I with a linear range of 2 nM to 2 μM in human serum [26]. Wang et al.
introduced a 13-mer peptide aptamer, immobilizing Troponin I on deposited gold
nanoparticles by using the thiol-functionality of the terminal cysteine [28]. This
approach achieved a linear range of 0.7–700 pM. Troponin I detection from clinical
samples showed fair recoveries of 91–105%.
Higher sensitivity was achieved by Akter et al. in 2017 by an antibody-based EIS
sensor [29]. Dendrimers between the electrode and the aptamer enhanced the
performance resulting in even lower detection limits of 11.7 fM and a linear range
of 46 fM to 46 nM. The lowest concentration measured in spiked serum was 460 fM.
Malaria results from an infection caused by parasites belonging to the Plasmodium family. P. falciparum and P. vivax are the main species which are transferred
by the Anopheles mosquito. In 2016, 216 million individuals were affected by
malaria and 445,000 died from it (see WHO malaria report 2017). Recommended
by the WHO as state-of-the-art blood diagnostics are microscopy and rapid diagnostic testing (RDTs) [30]. However, both methods show significant disadvantages:
While microscopy requires time and well-trained experts, RDTs based on antibodies
against Plasmodium lactate dehydrogenase (LDH) show limitations with regard to
costs, sensitivity at low concentrations, specificity, and thermal stability [31]. Nonetheless, since Plasmodium LDH is expressed in the sexual as well as the asexual
stage of the parasite, it is a reliable target for affinity-based sensors.
Lee et al. and Figueroa-Miranda et al. presented impedimetric aptasensors for
Plasmodium LDH determination from patient’s blood and diluted human serum
[31, 32]. In this way, they were able to distinguish between infected and uninfected
blood. A simple design based on co-immobilization of 6-mercapto-1-hexanol and
thiolated aptamer on a gold electrode resulted in a linear detection range of 1–1,000
pM [31]. Figueroa-Miranda et al. reported a linear range of 1 pM to 10 nM of the
50
J.-A. Preuß et al.