0.1 ppb with AFM1. Results revealed that the immune sensor has a low detection
limit (0.01 ppb), which was under the recommended level of AFM1 [0.05 μg L
–1
(ppb)], and has good reproducibility.
A new DNA-based biosensor for detection of aflatoxin M1 has been developed
by Dinckaya et al. (2011) based on an immobilization of thiol-modified singlestranded DNA (ss-HSDNA) probe that specifically binds to aflatoxin M1, a selfassembled monolayer (SAM) of cysteamine and gold nanoparticles on the SAM on
gold electrodes, layer-by-layer. The assembly processes of cysteamine, gold
nanoparticles, and ss-HSDNA were monitored with the help of electrochemical
impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques using potassium ferrocyanide as a redox probe for electrochemical measurements. The biosensor provided a linear response to aflatoxin M1 over the concentration range of
1–14 ng/mL with a standard deviation of Æ0.36 ng/ml.
3.6.3 Heavy Metals
Heavy metal ions, such as lead, mercury, cadmium, chromium, and arsenic, are
hazardous, contributing to water and soil pollution. Through water and soil, these
metal residues reach daily foods. Heavy metals are known to cause irreversible
changes in protein structures, affecting cell functions. Excessive intake of such
substances can result in adverse health conditions including neurological disorders,
renal degradation, and bone lesions (Kim et al. 2012). The nanobiosensing methods
for the detection of heavy metal ions can be divided into several subcategories
according to biorecognition molecule. Chen has developed an AuNPs-based duallabeling colorimetric method for Hg
2+ detection using a specific thymine–Hg
2+
–
thymine (T-Hg-T) (Tedsana et al. 2015) as a recognition system and dual-labeling
strategy for signal amplification; without using any instruments, they obtained a
LOD of 0.025 nM, competitive to other rapid detection methods (Dheng et al. 2015).
The target ions aid in assembling AuNPs modified with different Raman labels,
leading to different enhancements of Raman signal (Li et al. 2015). Saran and Liu
(2016) have used DNAzyme (recognition group and amplifier) for the development
of label-free catalytic biosensing platform for the detection of Pb
2+ and Ag
+ based on
stabilization of AgNCs (signal reporter) with DNA wherein these metals act as a
cofactor of DNAzyme activity (Gong et al. 2015). A study by Zhou et al. (2016) for
the specific detection of Cd
2+ and Pb
2+ by using amino acids because of the
functional side chain (like cysteine) wherein graphene oxide nanoparticles were
being used based on the change of the electrochemical signal. An approach by Fu
et al. (2015) for the detection of heavy metals (Cd
2+ ) by the use of antibody based on
core–shell AuNPs/AgNPs enhanced Raman scattering.
Sener et al. (2013) have developed a colorimetric assay based on the aggregation
of gold nanoparticles (AuNPs) in the presence of Hg
2+ . The detection limit of this
colorimetric assay is 2.9 nM, which is below the limit value (10 nM) defined by the
US Environmental Protection Agency. The colorimetric response of AuNPs in the
110
H. V. Raghu et al.
limit (0.01 ppb), which was under the recommended level of AFM1 [0.05 μg L
–1
(ppb)], and has good reproducibility.
A new DNA-based biosensor for detection of aflatoxin M1 has been developed
by Dinckaya et al. (2011) based on an immobilization of thiol-modified singlestranded DNA (ss-HSDNA) probe that specifically binds to aflatoxin M1, a selfassembled monolayer (SAM) of cysteamine and gold nanoparticles on the SAM on
gold electrodes, layer-by-layer. The assembly processes of cysteamine, gold
nanoparticles, and ss-HSDNA were monitored with the help of electrochemical
impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques using potassium ferrocyanide as a redox probe for electrochemical measurements. The biosensor provided a linear response to aflatoxin M1 over the concentration range of
1–14 ng/mL with a standard deviation of Æ0.36 ng/ml.
3.6.3 Heavy Metals
Heavy metal ions, such as lead, mercury, cadmium, chromium, and arsenic, are
hazardous, contributing to water and soil pollution. Through water and soil, these
metal residues reach daily foods. Heavy metals are known to cause irreversible
changes in protein structures, affecting cell functions. Excessive intake of such
substances can result in adverse health conditions including neurological disorders,
renal degradation, and bone lesions (Kim et al. 2012). The nanobiosensing methods
for the detection of heavy metal ions can be divided into several subcategories
according to biorecognition molecule. Chen has developed an AuNPs-based duallabeling colorimetric method for Hg
2+ detection using a specific thymine–Hg
2+
–
thymine (T-Hg-T) (Tedsana et al. 2015) as a recognition system and dual-labeling
strategy for signal amplification; without using any instruments, they obtained a
LOD of 0.025 nM, competitive to other rapid detection methods (Dheng et al. 2015).
The target ions aid in assembling AuNPs modified with different Raman labels,
leading to different enhancements of Raman signal (Li et al. 2015). Saran and Liu
(2016) have used DNAzyme (recognition group and amplifier) for the development
of label-free catalytic biosensing platform for the detection of Pb
2+ and Ag
+ based on
stabilization of AgNCs (signal reporter) with DNA wherein these metals act as a
cofactor of DNAzyme activity (Gong et al. 2015). A study by Zhou et al. (2016) for
the specific detection of Cd
2+ and Pb
2+ by using amino acids because of the
functional side chain (like cysteine) wherein graphene oxide nanoparticles were
being used based on the change of the electrochemical signal. An approach by Fu
et al. (2015) for the detection of heavy metals (Cd
2+ ) by the use of antibody based on
core–shell AuNPs/AgNPs enhanced Raman scattering.
Sener et al. (2013) have developed a colorimetric assay based on the aggregation
of gold nanoparticles (AuNPs) in the presence of Hg
2+ . The detection limit of this
colorimetric assay is 2.9 nM, which is below the limit value (10 nM) defined by the
US Environmental Protection Agency. The colorimetric response of AuNPs in the
110
H. V. Raghu et al.