Topics in Current Chemistry (2020) 378:12
1 3
a platform for the immobilization of a capture antibody, which was conjugated
onto a composite made of ferrocene and doped polypyrrole-AuNPs. The fabricated immunosensor showed a linear range from 1.0 × 10
1
to 1.0 × 10
7
colony
forming unit (CFU) mL
−1
and a low detection limit of 10 CFU mL
−1
.
Hoo et al. [216] recently reported the construction of an electrochemical glucose biosensor based on a nanocomposite of zinc oxide nanorods (ZnONRs) and
AuNps. In another example, AuNPs were then drop-casted on ZnONR/ITO substrates, while the GOx enzyme was immobilized with a matrix of Nafion onto the
modified electrode. The results suggest direct electron transfer from GOx enzymes
to the modified electrode. Moreover, the use of AuNPs can provide an additional
pathway that facilitates electron transfer. The optimized conditions for this bioelectrode were Nafion/60 µL GOx/80 µL 30 nm AuNP/ZnONR/ITO, exhibiting high
sensitivity of 14.53 and 2.54 µA mM
−1
cm
−2
for a wide working range of 0.05–1.0
and 1.0–20 mM and a low limit of detection (LOD) of 0.18 mM [216].
Buk and co-workers [217] reported a nanohybrid system based on carbon quantum dots (CQDs) and AuNPs for the design of enzymatic electrochemical biosensors using the CQDs/AuNPs as an immobilization matrix for a large surface area
microfabricated gold electrode. As a proof of concept, the GOx enzyme was chosen
as a model system, and immobilized onto the microfabricated gold electrode surface. GOx was conjugated a CQDs/AuNPs nanohybrid by cross-linking with glutaraldehyde. The biosensor exhibited high electrocatalytic activity, a good sensitivity
of 47.24 µA mM
−1
cm
−2
, reproducibility (5.4% relative standard deviation, RSD,
n = 5) and selectivity toward glucose, even in the presence of possible interfering
species. In continuation with the previous work, Buk et al. [218] developed an electrochemical biosensor from the system CDQs/AuNPs and gold microdisk array electrodes. The biosensor presented an improved analytical performance and a sensitivity of 626.06 mA mM
−1
cm
−2
with a linear range from 0.16 mM to 4.32 mM.
AuNPs coated with horseradish peroxidase (HRP) have been used to obtain
an electrochemical aptasensor for the detection of kanamycin, based on streptavidin–biotin supramolecular interactions (see Fig. 7). After a biotinylated aptamer of
kanamycin interacts with its complementary oligonucleotide strand modifying the
electrode, NPs coated with HRP and streptavidin are added to probe the formation
of the double-stranded DNA. Methylene blue is intercalated in the helical structure
obtained as electron mediator [219].
Another attractive application of AuNPs is their compatibility to conjugate antigenic carbohydrates [220]. Zhang et al. [221] described the design of a thioninebridged multiwalled carbon nanotube (MWCNT)/AuNP composite to detect a glycan on living cancer cells using enzyme catalysis. In such work, thionine allowed
negatively charged AuNPs to bind to the MWCNT surface. This biosensing platform
was used to quantify the amount of mannose at the surface of the cells, which corresponded to 3.39 × 10
10
molecules per human liver cancer cells, and 1.84 × 10
10
molecules for prostate cancer cells. Compared to other reported methods, this biosensor
provided a useful protocol for the glycan assay, facilitating early medical diagnosis.
In this regard, the field of biosensors has achieved remarkable advances in the
detection of cancer biomarkers [222]. Recently, Nguyen et al. [223] demonstrated
a simple microfluidic device for the capture of A549 human lung adenocarcinoma
114
Reprinted from the journal
1 3
a platform for the immobilization of a capture antibody, which was conjugated
onto a composite made of ferrocene and doped polypyrrole-AuNPs. The fabricated immunosensor showed a linear range from 1.0 × 10
1
to 1.0 × 10
7
colony
forming unit (CFU) mL
−1
and a low detection limit of 10 CFU mL
−1
.
Hoo et al. [216] recently reported the construction of an electrochemical glucose biosensor based on a nanocomposite of zinc oxide nanorods (ZnONRs) and
AuNps. In another example, AuNPs were then drop-casted on ZnONR/ITO substrates, while the GOx enzyme was immobilized with a matrix of Nafion onto the
modified electrode. The results suggest direct electron transfer from GOx enzymes
to the modified electrode. Moreover, the use of AuNPs can provide an additional
pathway that facilitates electron transfer. The optimized conditions for this bioelectrode were Nafion/60 µL GOx/80 µL 30 nm AuNP/ZnONR/ITO, exhibiting high
sensitivity of 14.53 and 2.54 µA mM
−1
cm
−2
for a wide working range of 0.05–1.0
and 1.0–20 mM and a low limit of detection (LOD) of 0.18 mM [216].
Buk and co-workers [217] reported a nanohybrid system based on carbon quantum dots (CQDs) and AuNPs for the design of enzymatic electrochemical biosensors using the CQDs/AuNPs as an immobilization matrix for a large surface area
microfabricated gold electrode. As a proof of concept, the GOx enzyme was chosen
as a model system, and immobilized onto the microfabricated gold electrode surface. GOx was conjugated a CQDs/AuNPs nanohybrid by cross-linking with glutaraldehyde. The biosensor exhibited high electrocatalytic activity, a good sensitivity
of 47.24 µA mM
−1
cm
−2
, reproducibility (5.4% relative standard deviation, RSD,
n = 5) and selectivity toward glucose, even in the presence of possible interfering
species. In continuation with the previous work, Buk et al. [218] developed an electrochemical biosensor from the system CDQs/AuNPs and gold microdisk array electrodes. The biosensor presented an improved analytical performance and a sensitivity of 626.06 mA mM
−1
cm
−2
with a linear range from 0.16 mM to 4.32 mM.
AuNPs coated with horseradish peroxidase (HRP) have been used to obtain
an electrochemical aptasensor for the detection of kanamycin, based on streptavidin–biotin supramolecular interactions (see Fig. 7). After a biotinylated aptamer of
kanamycin interacts with its complementary oligonucleotide strand modifying the
electrode, NPs coated with HRP and streptavidin are added to probe the formation
of the double-stranded DNA. Methylene blue is intercalated in the helical structure
obtained as electron mediator [219].
Another attractive application of AuNPs is their compatibility to conjugate antigenic carbohydrates [220]. Zhang et al. [221] described the design of a thioninebridged multiwalled carbon nanotube (MWCNT)/AuNP composite to detect a glycan on living cancer cells using enzyme catalysis. In such work, thionine allowed
negatively charged AuNPs to bind to the MWCNT surface. This biosensing platform
was used to quantify the amount of mannose at the surface of the cells, which corresponded to 3.39 × 10
10
molecules per human liver cancer cells, and 1.84 × 10
10
molecules for prostate cancer cells. Compared to other reported methods, this biosensor
provided a useful protocol for the glycan assay, facilitating early medical diagnosis.
In this regard, the field of biosensors has achieved remarkable advances in the
detection of cancer biomarkers [222]. Recently, Nguyen et al. [223] demonstrated
a simple microfluidic device for the capture of A549 human lung adenocarcinoma
114
Reprinted from the journal