presence of lysine is very selective to the Hg
2+ . Another attempt by Childress et al.
(2012) is by the use of dye-doped polymer nanoparticles that are able to detect
mercury in aqueous solution at parts per billion (ppb) levels via fluorescence
resonance energy transfer (FRET). The polymer NPs are synthesized by
re-precipitation of highly fluorescent conjugated polymers in water followed by
doping with rhodamine spirolactam dyes that are nonfluorescent until they encounter
mercury ions, which promote an irreversible reaction that converts the dyes to
fluorescent rhodamines. The rhodamine dyes act as FRET acceptors for the fluorescent nanoparticles, and the ratio of nanoparticle-to-rhodamine fluorescence intensities functions as a radio/ratiometric fluorescence chemodosimeter for mercury. The
light-harvesting capability of the conjugated polymer nanoparticles enhances the
fluorescence intensity of the rhodamine dyes by a factor of 10, enabling sensitive
detection of mercury ions at levels as low as 0.7 ppb.
3.6.4 Adulterants
Some manufacturers and farms engage in food fraud for increasing profit margin,
and such ill practices often lead to devastating results. Melamine, a chemical
adulterant, is sometimes illegally added to milk powder to improve the apparent
protein content (Niu et al. 2015). A melamine aptamer derived from a basic-sitecontaining triplex molecular beacon (tMB) has been proposed for sensitive recognition of melamine by integrating tMBs and fluorescent AgNCs (Wang et al. 2015).
Nitrite is harmful to humans and is widely used as an additive and preservative in
food service industry. A biosensor toward nitrite was developed based on the direct
electrochemistry of myoglobin on a reduced GOx-multi-walled CNTs-platinum NPs
nanocomposite (Mani et al. 2014). ZnO NPs are frequently considered to design
biosensing strategies for the detection of bisphenol A, a ubiquitous environmental
contaminant found in food products and aquatic ecosystems (Najafi et al. 2014;
Zhang et al. 2014). As H 2 O 2 is a kind of unlawful decolorizer for food, a biosensing
method toward H 2 O 2 was developed based on the H 2 O 2 enlarging AuNPs that
induced significant fluorescence quenching of BSA-AuNCs.
A highly sensitive acetylcholinesterase cyclic voltammetric biosensor based on
zinc oxide nanospheres modified Pt electrode has been successfully developed for
the simultaneous determination of melamine and urea in cow milk sample (Ezhilan
et al. 2017). The fabricated bioelectrode showed 100% permeability to the binary
mixture of melamine and urea, which in turn enhanced selectivity. The developed
Pt/ZnO/AChE/chitosan bioelectrode detected melamine and urea over a range of
1–20 nM with a limit of detection of 3 pM and 1 pM, respectively. The sensor
exhibited good recovery in the range of 99.96–102.22%, thus providing a promising
tool for analysis of melamine and urea in cow milk samples. Gold nanoparticles
functionalized with cyanuric acid compounds selectively bind to melamine, an
adulterant used to enhance the measured proteins content of infant food formulas
(Ai et al. 2009).
3 Application of Nanobiosensors for Food Safety Monitoring
111
2+ . Another attempt by Childress et al.
(2012) is by the use of dye-doped polymer nanoparticles that are able to detect
mercury in aqueous solution at parts per billion (ppb) levels via fluorescence
resonance energy transfer (FRET). The polymer NPs are synthesized by
re-precipitation of highly fluorescent conjugated polymers in water followed by
doping with rhodamine spirolactam dyes that are nonfluorescent until they encounter
mercury ions, which promote an irreversible reaction that converts the dyes to
fluorescent rhodamines. The rhodamine dyes act as FRET acceptors for the fluorescent nanoparticles, and the ratio of nanoparticle-to-rhodamine fluorescence intensities functions as a radio/ratiometric fluorescence chemodosimeter for mercury. The
light-harvesting capability of the conjugated polymer nanoparticles enhances the
fluorescence intensity of the rhodamine dyes by a factor of 10, enabling sensitive
detection of mercury ions at levels as low as 0.7 ppb.
3.6.4 Adulterants
Some manufacturers and farms engage in food fraud for increasing profit margin,
and such ill practices often lead to devastating results. Melamine, a chemical
adulterant, is sometimes illegally added to milk powder to improve the apparent
protein content (Niu et al. 2015). A melamine aptamer derived from a basic-sitecontaining triplex molecular beacon (tMB) has been proposed for sensitive recognition of melamine by integrating tMBs and fluorescent AgNCs (Wang et al. 2015).
Nitrite is harmful to humans and is widely used as an additive and preservative in
food service industry. A biosensor toward nitrite was developed based on the direct
electrochemistry of myoglobin on a reduced GOx-multi-walled CNTs-platinum NPs
nanocomposite (Mani et al. 2014). ZnO NPs are frequently considered to design
biosensing strategies for the detection of bisphenol A, a ubiquitous environmental
contaminant found in food products and aquatic ecosystems (Najafi et al. 2014;
Zhang et al. 2014). As H 2 O 2 is a kind of unlawful decolorizer for food, a biosensing
method toward H 2 O 2 was developed based on the H 2 O 2 enlarging AuNPs that
induced significant fluorescence quenching of BSA-AuNCs.
A highly sensitive acetylcholinesterase cyclic voltammetric biosensor based on
zinc oxide nanospheres modified Pt electrode has been successfully developed for
the simultaneous determination of melamine and urea in cow milk sample (Ezhilan
et al. 2017). The fabricated bioelectrode showed 100% permeability to the binary
mixture of melamine and urea, which in turn enhanced selectivity. The developed
Pt/ZnO/AChE/chitosan bioelectrode detected melamine and urea over a range of
1–20 nM with a limit of detection of 3 pM and 1 pM, respectively. The sensor
exhibited good recovery in the range of 99.96–102.22%, thus providing a promising
tool for analysis of melamine and urea in cow milk samples. Gold nanoparticles
functionalized with cyanuric acid compounds selectively bind to melamine, an
adulterant used to enhance the measured proteins content of infant food formulas
(Ai et al. 2009).
3 Application of Nanobiosensors for Food Safety Monitoring
111