Simultaneous Determination of Pesticides Using a Four-Band Disposable Optical Capillary Immunosensor

Abstract

The development of a four-band capillary optical immunosensor for the simultaneous determination of mesotrione, hexaconazole, paraquat, and diquat is described. Four distinct bands (each corresponding to a different analyte) are created in the internal walls of a plastic capillary by immobilizing protein conjugates of the analytes. To perform the assay, the capillary is filled with a mixture of anti-analyte-specific antibodies together with a standard or sample containing the analyte(s). After a short incubation, a mixture of the appropriate second antibodies labeled with fluorescein is introduced into the capillary. To measure the fluorescence intensity bound onto each band, the capillary was scanned, perpendicularly to its axis, by a laser light beam. Part of the emitted photons were trapped into the capillary walls and waveguided to a photomultiplier placed at the one end of the capillary. The analytical characteristics of the assays of mesotrione, paraquat, diquat, and hexaconazole were as follows: detection limits of 0.04, 0.06, 0.09, and 0.10 ng/mL, respectively; dynamic ranges up to 9, 6, 12, and 15 ng/ mL, respectively, intra- and interassay CVs less than 10%. The analytical characteristics of the assays were comparable with those of the corresponding single-analyte fluoroimmunoassays performed in microtitration wells, proving the ability of the proposed immunosensor for reliable multianalyte determinations. Moreover, the combination of low-cost disposable plastic capillary tubes with the low consumption of reagents, the short assay time, and the multianalyte feature of the proposed immunosensor indicates its potential for environmental analysis.

Bulk fluorescence light blockers to improve homogeneous detection in capillary-waveguide fluoroimmunosensors

“…Homogeneous signal monitoring of the binding reactions with the proposed immunosensor can be useful for the determination of antibodyantigen binding kinetics. Moreover, combining this feature with the multi-analyte potential of capillary fluoroimmunosensors (Petrou et al, 2002;Mastichiadis et al, 2002) can lead to fast, reliable and cost effective determinations of analyte panels with a single device.…”

“…As it has been reported, capillary sensors allow for the implementation of various set-up configurations concerning illumination and collection of emitted light O'Neil et al, 2006;Dhadwal et al, 2007). Amongst these, excitation of bound fluorescent molecules vertically to capillary axis and collection of the fluorescence waveguided through the capillary wall can lead to very sensitive Zhu et al, 2005;Bratcher et al, 2008) and multi-analyte assays (Petrou et al, 2002;Mastichiadis et al, 2002). In this case, performance of measurements in homogeneous detection mode (i.e., in presence of unreacted fluorescent molecules) has been also demonstrated (Badley et al, 1987;Misiakos and Kakabakos, 1998).…”

“…To evaluate the proposed approach, we employed a previously described capillary waveguide fluoroimmunosensor set-up (Petrou et al, 2002;Mastichiadis et al, 2002) schematically depicted in Fig. 1A.…”

Biosensors for environmental applications: Future development trends

“…Other studies aimed at the development of multianalyte immunosensors, such as that described by Gonzalez-Martínez et al [3], which developed a competitive capture assay for carbaryl, atrazine, and irgarol 1051 as target compounds. Mastichiadis et al [155] have applied recently an optical capillary immunosensor to the simultaneous determination of the pesticides mesotrione, hexaconazole, paraquat, and diquat, by preparing an ordered array capillary of four distinct analyte bands. After the optimal characterization of analytical conditions in deionized water, further experimentation is required in order to apply the biosensor to natural water sample analysis.…”

Screening methodologies for the determination of water contaminant residues by compact disk technology

“…Many fluorescence ELISAs have been developed for pesticide detection, such as for quantification of atrazine, 153 diuron, 154 and in multiplexed formats. 155 Chemiluminescent methods have been applied in routine clinical analysis as well as in clinical and biomedical researches due to the relatively simple instrumentation and high sensitivity. 156 In general, two chemiluminescent analytical reagents are used: (1) luminol or acridinium ester; (2) horseradish peroxidase or alkaline phosphatase, both as label for enzyme immunoassay.…”