4.1 Mycotoxins
Mycotoxins are metabolites produced by fungi that are toxic for humans and
animals. Fungi grow best in moisture and warm environments and thus, mycotoxins
are found in products grown in hot climates or stored and shipped for long periods
such as coffee beans or peanuts. The toxins withstand high temperatures and thus
remain active after heat treatment. Furthermore, mycotoxins do not induce an
immune response and thus are bypassing our immune system. To produce antibodies
against a mycotoxin, it needs to be bound to an immunogenic protein carrier which is
cumbersome. Therefore, especially for small molecules like mycotoxins, aptamers
are a perfect alternative recognition element in biosensors. The major groups of
mycotoxins are aflatoxin, ochratoxin, citrinin, ergot alkaloids, patulin, and fusarium
[102]. Vidal et al. published a review discussing electrochemical biosensors for the
detection of mycotoxins in food and they conclude that label-free and direct binding
properties, as impedimetric biosensors have, are beneficial in quality control in food
processing [103]. A list of aptamer-based impedimetric biosensors for the detection
of mycotoxins is presented in Table 9.
Aflatoxins are produced mainly by Aspergillus flavus, A. parasiticus, and
A. nomius, contaminants found in nuts and grains. Not only concentrations of
~10 μg/kg body weight have an acute hepatotoxic effect, but also concentrations
below are carcinogenic [102]. From 20 known types of aflatoxins, aflatoxin B 1
(AFB1) is considered the most prevalent, followed by aflatoxin B 2 , G 1 , and G 2 .
The European Commission set the limit for AFB1 in food products containing nuts
and grains depending on the kind and handling to 2–12 ppb (equivalent to 2–12 ng/g
or 6.4–38.4 nM) and for processed food intended for babies or children to 0.1 ng/g
(equivalent to 0.32 nM) [116].
Castillo et al. developed an aptamer-based impedimetric biosensor for the detection of AFB1 by using PAMAM G4 dendrimers on gold electrodes to increase the
Table 9 Impedimetric aptasensors for the detection of mycotoxins
Toxin Conc. range in g/ml LoD in pg/ml Real sample
Response
time
Reference
OTA
100 p to 25 m
100
–
15 min
[104]
OTA
40 p to 40 n
50
Coffee, flour, wine 30 min
[105]
OTA
120 p to 12 n
20
Beer
30 min
[106]
OTA
1 p to 0.5 n
0.2
Beer
1 h
[107]
OTA
4–40 p
6
White wine
90 min
[108]
OTA
2 p to 6 n
2
Wine
50 min
[109]
OTA
0.01 f to 0.1 n
10
À5
Soybean
9 min
[110]
OTA
0.1–10 p
0.05
Grape juice
5–7 min
[111]
AFB1 31 p to 2 n
100
Peanuts
40 min
[112]
AFB1 1 f to 1 n
0.4 Â 10
À3
Peanuts
3 h
[113]
AFM1 20 p to 1 n
1
Milk
30 min
[114]
FB1
72 p to 72 m
1
Maize
30 min
[115]
Impedimetric Aptamer-Based Biosensors: Applications
69
Mycotoxins are metabolites produced by fungi that are toxic for humans and
animals. Fungi grow best in moisture and warm environments and thus, mycotoxins
are found in products grown in hot climates or stored and shipped for long periods
such as coffee beans or peanuts. The toxins withstand high temperatures and thus
remain active after heat treatment. Furthermore, mycotoxins do not induce an
immune response and thus are bypassing our immune system. To produce antibodies
against a mycotoxin, it needs to be bound to an immunogenic protein carrier which is
cumbersome. Therefore, especially for small molecules like mycotoxins, aptamers
are a perfect alternative recognition element in biosensors. The major groups of
mycotoxins are aflatoxin, ochratoxin, citrinin, ergot alkaloids, patulin, and fusarium
[102]. Vidal et al. published a review discussing electrochemical biosensors for the
detection of mycotoxins in food and they conclude that label-free and direct binding
properties, as impedimetric biosensors have, are beneficial in quality control in food
processing [103]. A list of aptamer-based impedimetric biosensors for the detection
of mycotoxins is presented in Table 9.
Aflatoxins are produced mainly by Aspergillus flavus, A. parasiticus, and
A. nomius, contaminants found in nuts and grains. Not only concentrations of
~10 μg/kg body weight have an acute hepatotoxic effect, but also concentrations
below are carcinogenic [102]. From 20 known types of aflatoxins, aflatoxin B 1
(AFB1) is considered the most prevalent, followed by aflatoxin B 2 , G 1 , and G 2 .
The European Commission set the limit for AFB1 in food products containing nuts
and grains depending on the kind and handling to 2–12 ppb (equivalent to 2–12 ng/g
or 6.4–38.4 nM) and for processed food intended for babies or children to 0.1 ng/g
(equivalent to 0.32 nM) [116].
Castillo et al. developed an aptamer-based impedimetric biosensor for the detection of AFB1 by using PAMAM G4 dendrimers on gold electrodes to increase the
Table 9 Impedimetric aptasensors for the detection of mycotoxins
Toxin Conc. range in g/ml LoD in pg/ml Real sample
Response
time
Reference
OTA
100 p to 25 m
100
–
15 min
[104]
OTA
40 p to 40 n
50
Coffee, flour, wine 30 min
[105]
OTA
120 p to 12 n
20
Beer
30 min
[106]
OTA
1 p to 0.5 n
0.2
Beer
1 h
[107]
OTA
4–40 p
6
White wine
90 min
[108]
OTA
2 p to 6 n
2
Wine
50 min
[109]
OTA
0.01 f to 0.1 n
10
À5
Soybean
9 min
[110]
OTA
0.1–10 p
0.05
Grape juice
5–7 min
[111]
AFB1 31 p to 2 n
100
Peanuts
40 min
[112]
AFB1 1 f to 1 n
0.4 Â 10
À3
Peanuts
3 h
[113]
AFM1 20 p to 1 n
1
Milk
30 min
[114]
FB1
72 p to 72 m
1
Maize
30 min
[115]
Impedimetric Aptamer-Based Biosensors: Applications
69