Biosensors for pesticides - Electrochemical Sensors, Biosensors and Their Biomedical Applications - page 42

wave transducers [9]. Minunni and Mascini [76] used the commercial SPR apparatus
BIAcore™ from Pharmacia (Uppsala, Sweden) to detect the herbicide atrazine. This
non-labeled competitive device allowed achieving a detection limit of 0.05 ng mL 1 .
Mouvel et al . [77] reported an immunosensor based on waveguide surface plasmon
resonance (WSPR). The analyte derivatives were immobilized on modifi ed gold fi lm;
surface change caused by immunocomplexes was detected by silicon photodetectors.
The detection limit was 0.2 ng mL 1 . A label-free and highly sensitive immunosen-
sor using optical waveguide lightmode spectroscopy (OWLS) has been reported for the
detection of the herbicide trifl uralin [78]. The competitive assay allowed the detection
of trifl uralin in the concentration range of 2 10 5 ng mL 1 . A photo-

metric fl ow injection immunoassay has been reported for the determination of atrazine,
simazine, and 2,4-D by immobilizing the respective antibody on aminopropyl glass
particles by means of avidin/biotin conjugation [79]. Microcantilevers have also been
employed in the detection of pesticides. DDT-BSA conjugate has been immobilized on
a gold coated side of cantilever by using thiol self-assembled monolayers. The canti-
lever defl ection (shift of the resonant frequencies) occurred though indirect competitive
immunoassay was measured for the quantifi cation of DDT without any labeling [80].
In view of the fast detection and possibility of automatization, several fl ow injection
analysis biosensors have been reported. González-Martínez et al. [81] reported an FIA
immunosensor for carbaryl with special attention to assay sensitivity and sensor regen-
eration properties. This immunoassay used mouse monoclonal anti-carbaryl antibod-
ies either in solution (indirect format) or surface (direct format). In both formats, the
same enzyme label (HRP) and fl uorometric detection method was employed. A sensitive
detection (26 ng l 1 ) and fast response (11 min/assay) were obtained using direct immu-
noassay, while in indirect format the detection limit was 284 ng l 1 and the response
time was 17 min/assay. However, the useful life of the sensor was 60-70 cycles and
200 cycles for direct and indirect assays, respectively. During the regeneration steps
the antibody lost activity in direct competitive assay, whereas the pesticide underwent
regeneration in indirect assay, hence the sensor could be reused for longer. An ng mL 1
level detection of isoproturon has been reported using an optical immunosensor based
on solid phase fl uorescence immunoassay [82]. In this approach, analyte derivative was
immobilized on glass slides in agreement with the highest stability of the immobilization
structure. Detection limits for Milli-Q and river water samples were 0.01 and 0.14 ng
mL 1 , respectively. The major degradation product of the insecticides chlorpyrifos is
3,5,6-trichloro-2-pyridinol (TCP). The presence of TCP in human urine is considered as
a biomarker of exposure to chlorpyrifos insecticides. A fl ow injection immunosensor has
been reported for the detection of TCP, based on the immunocomplex formed in solution
by an antibody-binder protein A/G derivatized polymeric gel [83]. An optical immuno-
sensor coupled to an FIA system has been reported to monitor chlorotriazine pesticides
in river water samples [84]. In this study a solid-phase fl uorescence immunoassay was
employed with immobilized analyte derivative and free, fl uorescence-labeled anti-atrazine
or anti-simazine. The limits of detection for atrazine and simazine varied between 0.06
and 0.2 ng mL 1 , depending on Milli-Q water or river water samples used.
Multianalyte immunosensor is highly advantageous for fi eld applications. It allows
several compounds in a single run to be determined, irrespective to the nature of the

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