emission of strong fluorescence due to an intramolecular energy transfer from Tc to
Eu3+. The fluorescence intensity of this probe displayed a good linear response to Tc
concentrations in the range of 10 nM to 10 μM with a detection limit of 4 nM and
was applied successfully to determine the levels of Tc in milk with a high selectivity.
3.6.2 Aflatoxin M1
Aflatoxins are secondary metabolites when ingested by animals, and higher vertebrates cause diverse health effects and disease called aflatoxicosis (Adegoke and
Puleng 2013). Aflatoxin-contaminated/aflatoxin-containing agricultural and dairy
products meet great economic losses (Cleveland et al. 2003). Studies by various
researchers have shown that in the storage processes or cultivation of grains showed
different levels of contamination, especially with aflatoxin B1 (AFB1) (Caldas et al.
2002). AFB1 is a powerful genotoxic carcinogen for humans and many animal
species, including rodents, nonhuman primates, and fish (EC 2012). The main target
of this carcinogen is the liver, although tumors may also develop in other organs,
such as the lungs, kidney, and colon (Gelderblom et al. 1996). The current maximum
residue levels for aflatoxins set by the European community (EC) are 20 μg/kg for
AFB1 and 40 μg/kg for total aflatoxins in groundnuts, nuts, dried fruits, and cereals
for direct human consumption (EC 2006). Aflatoxin M1 (AFM1), as the hydroxylated metabolite of aflatoxin B1 (AFB1), is usually present in the animal milk
contaminated by AFB1. Because of their stronger toxic effects than AFB1 on public
health, many governments have provided maximum acceptable limits for residual
AFM1 in foodstuffs, especially in milk products (Kadir and Tothill 2010). For
example, according to FSSAI standards, aflatoxin M1 content cannot exceed
0.5 μg/kg in milk, whereas the European–USA has higher regulations of 50 ng/kg.
Thus, the food administration agencies in almost all countries have dedicated much
effort to developing sensitive analytical methods for monitoring ultra-trace levels of
AFM1 (<0.05 μg/kg) in foods (Hansmann et al. 2009). Current strategies for
ultrasensitive detection of AFM1 are based mainly on thin-layer chromatography
(TLC), high-performance liquid chromatography (HPLC), or UV light spectroscopy
after extraction and clean-up procedures (Amine et al. 2003). These methods are
adequately sensitive and accurate; however, they often require sophisticated, expensive, and heavy instruments that may not be available in laboratories with fewer
resources; these methods are especially not fit for mass screening (Gan et al. 2013).
The Zhang group developed a rapid method for detection of aflatoxin M1 by
coupling superparamagnetic beads with gold labels (Zhang et al. 2013). The recent
development of nanobiosensors has roused their application also to aflatoxin analysis. Many examples are reported, like DNA biosensor (Tombelli et al. 2009),
electrochemical immune sensor (Linting et al. 2012), an electrochemical sensor
(Liu et al. 2006), and the fluorometric biosensor (Carlson et al. 2000). Advantages
of nanobiosensors techniques are a reduction of extraction, clean-up analytical steps,
and global time of analysis (1 min or only a few seconds), the possibility of online
3 Application of Nanobiosensors for Food Safety Monitoring
107
Eu3+. The fluorescence intensity of this probe displayed a good linear response to Tc
concentrations in the range of 10 nM to 10 μM with a detection limit of 4 nM and
was applied successfully to determine the levels of Tc in milk with a high selectivity.
3.6.2 Aflatoxin M1
Aflatoxins are secondary metabolites when ingested by animals, and higher vertebrates cause diverse health effects and disease called aflatoxicosis (Adegoke and
Puleng 2013). Aflatoxin-contaminated/aflatoxin-containing agricultural and dairy
products meet great economic losses (Cleveland et al. 2003). Studies by various
researchers have shown that in the storage processes or cultivation of grains showed
different levels of contamination, especially with aflatoxin B1 (AFB1) (Caldas et al.
2002). AFB1 is a powerful genotoxic carcinogen for humans and many animal
species, including rodents, nonhuman primates, and fish (EC 2012). The main target
of this carcinogen is the liver, although tumors may also develop in other organs,
such as the lungs, kidney, and colon (Gelderblom et al. 1996). The current maximum
residue levels for aflatoxins set by the European community (EC) are 20 μg/kg for
AFB1 and 40 μg/kg for total aflatoxins in groundnuts, nuts, dried fruits, and cereals
for direct human consumption (EC 2006). Aflatoxin M1 (AFM1), as the hydroxylated metabolite of aflatoxin B1 (AFB1), is usually present in the animal milk
contaminated by AFB1. Because of their stronger toxic effects than AFB1 on public
health, many governments have provided maximum acceptable limits for residual
AFM1 in foodstuffs, especially in milk products (Kadir and Tothill 2010). For
example, according to FSSAI standards, aflatoxin M1 content cannot exceed
0.5 μg/kg in milk, whereas the European–USA has higher regulations of 50 ng/kg.
Thus, the food administration agencies in almost all countries have dedicated much
effort to developing sensitive analytical methods for monitoring ultra-trace levels of
AFM1 (<0.05 μg/kg) in foods (Hansmann et al. 2009). Current strategies for
ultrasensitive detection of AFM1 are based mainly on thin-layer chromatography
(TLC), high-performance liquid chromatography (HPLC), or UV light spectroscopy
after extraction and clean-up procedures (Amine et al. 2003). These methods are
adequately sensitive and accurate; however, they often require sophisticated, expensive, and heavy instruments that may not be available in laboratories with fewer
resources; these methods are especially not fit for mass screening (Gan et al. 2013).
The Zhang group developed a rapid method for detection of aflatoxin M1 by
coupling superparamagnetic beads with gold labels (Zhang et al. 2013). The recent
development of nanobiosensors has roused their application also to aflatoxin analysis. Many examples are reported, like DNA biosensor (Tombelli et al. 2009),
electrochemical immune sensor (Linting et al. 2012), an electrochemical sensor
(Liu et al. 2006), and the fluorometric biosensor (Carlson et al. 2000). Advantages
of nanobiosensors techniques are a reduction of extraction, clean-up analytical steps,
and global time of analysis (1 min or only a few seconds), the possibility of online
3 Application of Nanobiosensors for Food Safety Monitoring
107