Topics in Current Chemistry (2020) 378:12
1 3
selectivity with a detection limit of 0.15 nM. Likewise, Aftab et al. [229] recently
published a sensitive voltammetric nanosensor for the detection of Rilpivirine (RIL)
based on amine group functionalized MWCNT, CQDs and AgNPs (CQDs/NH 2 -
fMWCNT/AgNPs). The nanosensor allowed detection of RIL in biological samples
with LOD of 1.79 × 10
−10
M, 4.47 × 10
−10
M in serum sample and 5.26 × 10
−10
M,
8.23 × 10
−10
M.
There is a significant interest in the early detection of different types of cancer.
Meng et al. [230] developed an electrochemical biosensor for the sensitive analysis
of prostate-specific antigen (PSA) based on a specific peptide as a molecular recognition element. The peptide was immobilized onto a gold electrode surface. In the
absence of PSA, GO is immobilized on the peptide-modified electrode. In turn, it
allows the silver ions to be absorbed onto GO through electrostatic interactions. GO
acts as a reducing and dispersing agent, facilitating the formation of AgNPs, which
contributes to better electronic transport and hence to the analytical signal. In the
presence of PSA, the peptide is specifically recognized and cleaved at the surface of
the electrode. The biosensor displayed high sensitivity, selectivity and a linear range
from 5 to 2 × 10
4
pg/mL, with a LOD of 0.33 pg/mL.
Elhakim et al. [231] designed a novel sensitive electrochemical sensor for microribonucleic acid (microRNA) detection in normal serum samples, hepatocellular carcinoma patients and human liver cancer cells. The biosensor constructed consisted
in a carbon paste (CP) decorated with AgNPs and extracted propolis (bee glue). The
porous structure of propolis allowed the AgNPs to be adsorbed, increasing the surface area of the sensor, facilitating the charge transfer process. The microRNA was
also immobilized on the surface of the electrode through trapping with propoleos.
The biosensor presented high selectivity and sensitivity, and a very low detection
limit of 10
−3
femtomolar.
Chen and co-authors reported the fabrication of inexpensive and flexible electronic and electrochemical sensors for a wide range of biochemical and biomedical applications [232]. The electrochemical biosensor was fabricated by a simple
method involving wax patterning on plastic, hand painting of AgNPs to lay down
a conducting layer, and simple drop casting of carbon nanotubes (CNT) to improve
the electrochemical performance of the sensor. The nanosensor was applied for the
amperometric detection of carcinoembryonic antigen (CEA) by monitoring an electroactive product released from a magnetic-bead based immunoassay. The limit of
detection for CEA found to be 0.46 ng/mL, which is 10 times lower than the clinical
cutoff value. The results of this work show that the improvement in electrochemical
performance can be achieved by simple drop casting of CNT onto working AgNP
electrodes.
6.3 Electrochemical Applications of Bioconjugates Based on IONPs
MNPs are also used widely in the development of biosensors. In this sense, magnetic IONPs have been studied intensively due to their strong magnetic properties,
electrocatalytic activity, biocompatibility with biomolecules, inexpensive synthesis
and low toxicity [108, 130]. For example, electrocatalytic processes on the electrode
116
Reprinted from the journal
1 3
selectivity with a detection limit of 0.15 nM. Likewise, Aftab et al. [229] recently
published a sensitive voltammetric nanosensor for the detection of Rilpivirine (RIL)
based on amine group functionalized MWCNT, CQDs and AgNPs (CQDs/NH 2 -
fMWCNT/AgNPs). The nanosensor allowed detection of RIL in biological samples
with LOD of 1.79 × 10
−10
M, 4.47 × 10
−10
M in serum sample and 5.26 × 10
−10
M,
8.23 × 10
−10
M.
There is a significant interest in the early detection of different types of cancer.
Meng et al. [230] developed an electrochemical biosensor for the sensitive analysis
of prostate-specific antigen (PSA) based on a specific peptide as a molecular recognition element. The peptide was immobilized onto a gold electrode surface. In the
absence of PSA, GO is immobilized on the peptide-modified electrode. In turn, it
allows the silver ions to be absorbed onto GO through electrostatic interactions. GO
acts as a reducing and dispersing agent, facilitating the formation of AgNPs, which
contributes to better electronic transport and hence to the analytical signal. In the
presence of PSA, the peptide is specifically recognized and cleaved at the surface of
the electrode. The biosensor displayed high sensitivity, selectivity and a linear range
from 5 to 2 × 10
4
pg/mL, with a LOD of 0.33 pg/mL.
Elhakim et al. [231] designed a novel sensitive electrochemical sensor for microribonucleic acid (microRNA) detection in normal serum samples, hepatocellular carcinoma patients and human liver cancer cells. The biosensor constructed consisted
in a carbon paste (CP) decorated with AgNPs and extracted propolis (bee glue). The
porous structure of propolis allowed the AgNPs to be adsorbed, increasing the surface area of the sensor, facilitating the charge transfer process. The microRNA was
also immobilized on the surface of the electrode through trapping with propoleos.
The biosensor presented high selectivity and sensitivity, and a very low detection
limit of 10
−3
femtomolar.
Chen and co-authors reported the fabrication of inexpensive and flexible electronic and electrochemical sensors for a wide range of biochemical and biomedical applications [232]. The electrochemical biosensor was fabricated by a simple
method involving wax patterning on plastic, hand painting of AgNPs to lay down
a conducting layer, and simple drop casting of carbon nanotubes (CNT) to improve
the electrochemical performance of the sensor. The nanosensor was applied for the
amperometric detection of carcinoembryonic antigen (CEA) by monitoring an electroactive product released from a magnetic-bead based immunoassay. The limit of
detection for CEA found to be 0.46 ng/mL, which is 10 times lower than the clinical
cutoff value. The results of this work show that the improvement in electrochemical
performance can be achieved by simple drop casting of CNT onto working AgNP
electrodes.
6.3 Electrochemical Applications of Bioconjugates Based on IONPs
MNPs are also used widely in the development of biosensors. In this sense, magnetic IONPs have been studied intensively due to their strong magnetic properties,
electrocatalytic activity, biocompatibility with biomolecules, inexpensive synthesis
and low toxicity [108, 130]. For example, electrocatalytic processes on the electrode
116
Reprinted from the journal