absence of Salmonella in 25 g of meat, gelatin, collagen, milk products, eggs, and
many kinds of ready-to-eat products including sea food, fruits, and vegetables [142].
Ma et al. developed an aptamer-based faradaic impedance biosensor for the
detection of S. typhimurium by modifying a glassy carbon electrode with a
nanocomposite of graphene oxide and gold nanoparticles [129]. They reached a
detection limit (LoD) of 3 colony forming units (CFU) per ml in buffer and a linear
range from 2.4 to 2.4 Â 10
3 CFU/ml with a sensitivity of 706 Ohm per decade. The
high specificity of the biosensor was shown with a 12 times higher signal for
S. typhimurium compared to L. monocytogenes, B. subtilis, S. aureus, S. pyogenes,
E. coli, and Enterobacter sakazakii. Performance was verified in spiked pork
samples with recovery rates of 97–105%. With an incubation time of 35 min, the
whole measurement can be performed within 40–50 min, which is significantly
faster than a real-time PCR, taking 2 h and reaching a LoD of 78 CFU/ml [132].
An impressing detection limit of 1 CFU/ml was achieved by Ranjibar et al. by
nanoporous gold electrodes modified with thiolated aptamers [130]. The developed
impedimetric aptasensor has a wide dynamic range (6.5 Â 10
2
–6.5 Â 10
8 CFU/ml)
with a sensitivity of 841 Ohm per decade and a high selectivity with a 7 times higher
signal for S. typhimurium compared to S. aureus, E. coli, and Pseudomonas.
Recovery rates from spiked egg samples were 85–110% and the RSD from repeated
Table 10 Impedimetric aptasensors for the detection of microorganisms and their toxins in food
Analyte
Method
LoD in
CFU/ml
Real sample
Incubation time in
min
Reference
S. typhimurium
EIS
600
–
60
[125]
S. typhimurium
EIS
25
Chicken
meat
60
[126]
S. typhimurium
EIS
6
Apple juice
60
[127]
S. typhimurium
EIS
3
Apple juice
45
[128]
S. typhimurium
EIS
3
Pork meat
35
[129]
S. typhimurium
EIS
1
Egg
40
[130]
S. typhimurium
CA
20
Chicken
meat
120
[131]
S. typh. and
E. coli
RTPCR
78
Milk
120
[132]
S. tnteritidis
EIS
600
–
60
[133]
E. coli
EIS
2 Â 10
4
–
60
[134]
E. coli
EIS
4
–
12
[135]
E. coli
EIS
12
Milk
120
[136]
Listeria
EIS
100
–
<180
[137]
L. monocytogenes EIS
5
–
17
[138]
S. aureus
EIS
10
Fish and
water
60
[139]
S. aureus
EIS
10
–
10
[140]
SEB
EIS
6 pM
Milk
100
[141]
74
J.-A. Preuß et al.
many kinds of ready-to-eat products including sea food, fruits, and vegetables [142].
Ma et al. developed an aptamer-based faradaic impedance biosensor for the
detection of S. typhimurium by modifying a glassy carbon electrode with a
nanocomposite of graphene oxide and gold nanoparticles [129]. They reached a
detection limit (LoD) of 3 colony forming units (CFU) per ml in buffer and a linear
range from 2.4 to 2.4 Â 10
3 CFU/ml with a sensitivity of 706 Ohm per decade. The
high specificity of the biosensor was shown with a 12 times higher signal for
S. typhimurium compared to L. monocytogenes, B. subtilis, S. aureus, S. pyogenes,
E. coli, and Enterobacter sakazakii. Performance was verified in spiked pork
samples with recovery rates of 97–105%. With an incubation time of 35 min, the
whole measurement can be performed within 40–50 min, which is significantly
faster than a real-time PCR, taking 2 h and reaching a LoD of 78 CFU/ml [132].
An impressing detection limit of 1 CFU/ml was achieved by Ranjibar et al. by
nanoporous gold electrodes modified with thiolated aptamers [130]. The developed
impedimetric aptasensor has a wide dynamic range (6.5 Â 10
2
–6.5 Â 10
8 CFU/ml)
with a sensitivity of 841 Ohm per decade and a high selectivity with a 7 times higher
signal for S. typhimurium compared to S. aureus, E. coli, and Pseudomonas.
Recovery rates from spiked egg samples were 85–110% and the RSD from repeated
Table 10 Impedimetric aptasensors for the detection of microorganisms and their toxins in food
Analyte
Method
LoD in
CFU/ml
Real sample
Incubation time in
min
Reference
S. typhimurium
EIS
600
–
60
[125]
S. typhimurium
EIS
25
Chicken
meat
60
[126]
S. typhimurium
EIS
6
Apple juice
60
[127]
S. typhimurium
EIS
3
Apple juice
45
[128]
S. typhimurium
EIS
3
Pork meat
35
[129]
S. typhimurium
EIS
1
Egg
40
[130]
S. typhimurium
CA
20
Chicken
meat
120
[131]
S. typh. and
E. coli
RTPCR
78
Milk
120
[132]
S. tnteritidis
EIS
600
–
60
[133]
E. coli
EIS
2 Â 10
4
–
60
[134]
E. coli
EIS
4
–
12
[135]
E. coli
EIS
12
Milk
120
[136]
Listeria
EIS
100
–
<180
[137]
L. monocytogenes EIS
5
–
17
[138]
S. aureus
EIS
10
Fish and
water
60
[139]
S. aureus
EIS
10
–
10
[140]
SEB
EIS
6 pM
Milk
100
[141]
74
J.-A. Preuß et al.