3.6.5 Pesticide Residues
Various kinds of nanoparticles, such as quantum dots (QDs) and AuNPs, have been
used for the development of electrochemical enzyme biosensors. An enzyme biosensor was developed for the amperometric detection of trichlorfon using poly
(N-vinyl-2-pyrrolidone) (PVP)-capped CdS QDs (Li et al. 2006). The formation of
PVP-QD nanostructures on the electrode surface provided a favorable microenvironment and led to a highly sensitive and stable electrochemical detection of the
enzymatically generated thiocholine product. The detection limit was 4.8 Â 10–8 M.
Another kind of nanoparticles is AuNPs. Their unique property to provide a suitable
microenvironment for immobilization of biomolecules retaining their bioactivity is a
major advantage for the preparation of biosensors. Moreover, AuNPs facilitate direct
electron transfer between immobilized redox proteins and the electrode surface
(Pingarron et al. 2008). An electrochemical biosensor based on the colloidal
AuNP-modified sol–gel interface was developed for the detection of
monocrotophos, carbaryl, and methyl parathion (Du et al. 2008a). The assembled
AuNPs on a sol–gel-derived silicate network provided a conductive pathway to
electron transfer and favored the interface enzymatic hydrolysis reaction, increasing
the sensitivity of the amperometric response. This biosensor presented good stability, retaining 90% of its initial current response after a 30-day storage period.
Recently, an efficient biosensor for the detection of monocrotophos was developed
by combining the unique properties of AuNPs with those of QDs. This new
electrochemical system based on CdTe QD-AuNP electrode was more sensitive
than those based on QDs or AuNPs alone (Du et al. 2008b).
Recently, an electrochemical immune sensor was developed for rapid screening
of diuron, a substituted phenyl urea herbicide (Sharma et al. 2011). Low-cost ablated
electrodes fabricated on polystyrene substrate were modified with Prussian Blue
(PB)-AuNP film. The electrodeposition of PBAuNP film enhanced electron transfer
in the vicinity of the gold electrode increasing the sensitivity of the system as
compared to unmodified gold electrodes. A conductometric immune sensor for the
detection of atrazine was also developed using antibodies labeled with nanoparticles
(Valera et al. 2008). The authors showed that AuNPs amplify the conductive signal
and hence allow the detection of atrazine by means of DC measurements.
Nanoparticles have also been used for the development of efficient optical biosensors (Lin et al. 2006). QDs are candidates to replace conventional fluorescent
markers. These semiconductor particles are more photostable than an organic
fluorophore. Moreover, QDs exhibit higher fluorescence quantum yields than conventional organic fluorophores, allowing higher sensitivity. Recently, an optical
biosensor was developed for the detection of monocrotophos using CdTe as fluorescence probe (Sun et al. 2011). Using positively charged chitosan, CdTe and
acetylcholinesterase were assembled onto a quartz surface by a layer-by-layer
technique. In the absence of pesticide, acetylcholine was bio-catalytically
hydrolyzed inducing the production of choline and acetic acid. The released acid
resulted in pH decrease that was sensed by the immobilized pH indicator (CdTe).
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H. V. Raghu et al.
Various kinds of nanoparticles, such as quantum dots (QDs) and AuNPs, have been
used for the development of electrochemical enzyme biosensors. An enzyme biosensor was developed for the amperometric detection of trichlorfon using poly
(N-vinyl-2-pyrrolidone) (PVP)-capped CdS QDs (Li et al. 2006). The formation of
PVP-QD nanostructures on the electrode surface provided a favorable microenvironment and led to a highly sensitive and stable electrochemical detection of the
enzymatically generated thiocholine product. The detection limit was 4.8 Â 10–8 M.
Another kind of nanoparticles is AuNPs. Their unique property to provide a suitable
microenvironment for immobilization of biomolecules retaining their bioactivity is a
major advantage for the preparation of biosensors. Moreover, AuNPs facilitate direct
electron transfer between immobilized redox proteins and the electrode surface
(Pingarron et al. 2008). An electrochemical biosensor based on the colloidal
AuNP-modified sol–gel interface was developed for the detection of
monocrotophos, carbaryl, and methyl parathion (Du et al. 2008a). The assembled
AuNPs on a sol–gel-derived silicate network provided a conductive pathway to
electron transfer and favored the interface enzymatic hydrolysis reaction, increasing
the sensitivity of the amperometric response. This biosensor presented good stability, retaining 90% of its initial current response after a 30-day storage period.
Recently, an efficient biosensor for the detection of monocrotophos was developed
by combining the unique properties of AuNPs with those of QDs. This new
electrochemical system based on CdTe QD-AuNP electrode was more sensitive
than those based on QDs or AuNPs alone (Du et al. 2008b).
Recently, an electrochemical immune sensor was developed for rapid screening
of diuron, a substituted phenyl urea herbicide (Sharma et al. 2011). Low-cost ablated
electrodes fabricated on polystyrene substrate were modified with Prussian Blue
(PB)-AuNP film. The electrodeposition of PBAuNP film enhanced electron transfer
in the vicinity of the gold electrode increasing the sensitivity of the system as
compared to unmodified gold electrodes. A conductometric immune sensor for the
detection of atrazine was also developed using antibodies labeled with nanoparticles
(Valera et al. 2008). The authors showed that AuNPs amplify the conductive signal
and hence allow the detection of atrazine by means of DC measurements.
Nanoparticles have also been used for the development of efficient optical biosensors (Lin et al. 2006). QDs are candidates to replace conventional fluorescent
markers. These semiconductor particles are more photostable than an organic
fluorophore. Moreover, QDs exhibit higher fluorescence quantum yields than conventional organic fluorophores, allowing higher sensitivity. Recently, an optical
biosensor was developed for the detection of monocrotophos using CdTe as fluorescence probe (Sun et al. 2011). Using positively charged chitosan, CdTe and
acetylcholinesterase were assembled onto a quartz surface by a layer-by-layer
technique. In the absence of pesticide, acetylcholine was bio-catalytically
hydrolyzed inducing the production of choline and acetic acid. The released acid
resulted in pH decrease that was sensed by the immobilized pH indicator (CdTe).
112
H. V. Raghu et al.