completely eliminate the color development step, thus simplifying the analysis of
AFM. A linear relationship was observed between the inhibition values and the
concentrations of AFM in both buffer solution (0–1000 ngÁL
–1 ) and spiked milk
samples (0–400 ngÁL
–1 ). The limit of detection was found to be 37.7 ngÁL
–1 for AFM
in buffer solution and 27.5 ngÁL
–1 in milk samples.
An ultrasensitive electro-chemiluminescent immunoassay (ECLIA) for aflatoxins
M1 (AFM1) in milk using magnetic Fe 3 O 4 -graphene oxides (Fe-GO) as the absorbent and antibody-labeled cadmium telluride quantum dots (CdTe QDs) as the signal
tag (Gan et al. 2013). Firstly, Fe 3 O 4 nanoparticles are immobilized on graphene
oxides to fabricate the magnetic nanocomposites, which are used as absorbent to
AFM1. Secondly, aflatoxin M1 antibody (primary antibody, AFM1 Ab1) is attached
to the surface of the CdTe QDs-carbon nanotubes nanocomposite to form the signal
tag (AFM1 Ab1/CdTe-CNT). Thirdly, Fe-GO was employed for extraction of
AFM1 in milk wherein it can adsorb AFM1 efficiently and selectively within a
large extent of pH from 3.0 to 8.0. Adsorption processes reached 95% of the
equilibrium within 10 min (Gan et al. 2016). Lastly, the AFM1 with a serial of
concentrations absorbed on Fe-GO was conjugated with AFM1 Ab1/CdTe-CNT
signal tag based on sandwich immunoassay. The immuno-complex can emit a strong
ECL signal whose intensity depended linearly on the logarithm of AFM1 concentration from 1.0 to 1.0 Â 10
5 pg/mL, with the detection limit (LOD) of 0.3 pg/mL
(S/N ¼ 3). The method was more sensitive for AFM1 detection compared to the
ELISA method.
Pal et al. (2015) have developed a multi-platform detection of AFM1 based on
hafnia nanoparticles based on immunochemistry. The fine-grained nanocrystal
ceramic powder samples of HfO 2 NP 2 were prepared, and they are highly specific
to the monoclonal antibody immobilized onto HfO 2 surface using chemical modification and cross-linking chemistry. Further, nanobiosensors were evaluated based on
chemiluminescent sandwich enzyme-linked immunosorbent assay followed by photometric measurement of particles with a detection limit of 200–0.5 pg/ml. the multiplatform detection having a good linearity with a limit of detection 6.25 pg/ml,
sensitivity, selectivity, and stability.
An electrochemical immune sensor for the detection of ultra-trace amounts of
aflatoxin M1 (AFM1) in food products has been developed by Paniel et al. (2010).
The sensor was based on a competitive immunoassay using horseradish peroxidase
(HRP) as a tag. Magnetic nanoparticles coated with antibody (anti-AFM1) were used
to separate the bound and unbound fractions. The samples containing AFM1 were
incubated with a fixed amount of antibody and tracer [AFM1 linked to HRP
(conjugate)] until the system reached equilibrium. Competition occurs between the
antigen (AFM1) and the conjugate for the antibody. Then, the mixture was deposited
on the surface of screen-printed carbon electrodes, and the mediator
[5-methylphenazinium methyl sulfate (MPMS)] was added. The enzymatic response
was measured amperometrically. A standard range (0, 0.005, 0.01, 0.025, 0.05, 0.1,
0.25, 0.3, 0.4 and 0.5 ppb) of AFM1-contaminated milk from the ELISA kit was
used to obtain a standard curve for AFM1. To test the detection sensitivity of the
sensor, samples of commercial milk were supplemented at 0.01, 0.025, 0.05, or
3 Application of Nanobiosensors for Food Safety Monitoring
109
AFM. A linear relationship was observed between the inhibition values and the
concentrations of AFM in both buffer solution (0–1000 ngÁL
–1 ) and spiked milk
samples (0–400 ngÁL
–1 ). The limit of detection was found to be 37.7 ngÁL
–1 for AFM
in buffer solution and 27.5 ngÁL
–1 in milk samples.
An ultrasensitive electro-chemiluminescent immunoassay (ECLIA) for aflatoxins
M1 (AFM1) in milk using magnetic Fe 3 O 4 -graphene oxides (Fe-GO) as the absorbent and antibody-labeled cadmium telluride quantum dots (CdTe QDs) as the signal
tag (Gan et al. 2013). Firstly, Fe 3 O 4 nanoparticles are immobilized on graphene
oxides to fabricate the magnetic nanocomposites, which are used as absorbent to
AFM1. Secondly, aflatoxin M1 antibody (primary antibody, AFM1 Ab1) is attached
to the surface of the CdTe QDs-carbon nanotubes nanocomposite to form the signal
tag (AFM1 Ab1/CdTe-CNT). Thirdly, Fe-GO was employed for extraction of
AFM1 in milk wherein it can adsorb AFM1 efficiently and selectively within a
large extent of pH from 3.0 to 8.0. Adsorption processes reached 95% of the
equilibrium within 10 min (Gan et al. 2016). Lastly, the AFM1 with a serial of
concentrations absorbed on Fe-GO was conjugated with AFM1 Ab1/CdTe-CNT
signal tag based on sandwich immunoassay. The immuno-complex can emit a strong
ECL signal whose intensity depended linearly on the logarithm of AFM1 concentration from 1.0 to 1.0 Â 10
5 pg/mL, with the detection limit (LOD) of 0.3 pg/mL
(S/N ¼ 3). The method was more sensitive for AFM1 detection compared to the
ELISA method.
Pal et al. (2015) have developed a multi-platform detection of AFM1 based on
hafnia nanoparticles based on immunochemistry. The fine-grained nanocrystal
ceramic powder samples of HfO 2 NP 2 were prepared, and they are highly specific
to the monoclonal antibody immobilized onto HfO 2 surface using chemical modification and cross-linking chemistry. Further, nanobiosensors were evaluated based on
chemiluminescent sandwich enzyme-linked immunosorbent assay followed by photometric measurement of particles with a detection limit of 200–0.5 pg/ml. the multiplatform detection having a good linearity with a limit of detection 6.25 pg/ml,
sensitivity, selectivity, and stability.
An electrochemical immune sensor for the detection of ultra-trace amounts of
aflatoxin M1 (AFM1) in food products has been developed by Paniel et al. (2010).
The sensor was based on a competitive immunoassay using horseradish peroxidase
(HRP) as a tag. Magnetic nanoparticles coated with antibody (anti-AFM1) were used
to separate the bound and unbound fractions. The samples containing AFM1 were
incubated with a fixed amount of antibody and tracer [AFM1 linked to HRP
(conjugate)] until the system reached equilibrium. Competition occurs between the
antigen (AFM1) and the conjugate for the antibody. Then, the mixture was deposited
on the surface of screen-printed carbon electrodes, and the mediator
[5-methylphenazinium methyl sulfate (MPMS)] was added. The enzymatic response
was measured amperometrically. A standard range (0, 0.005, 0.01, 0.025, 0.05, 0.1,
0.25, 0.3, 0.4 and 0.5 ppb) of AFM1-contaminated milk from the ELISA kit was
used to obtain a standard curve for AFM1. To test the detection sensitivity of the
sensor, samples of commercial milk were supplemented at 0.01, 0.025, 0.05, or
3 Application of Nanobiosensors for Food Safety Monitoring
109