Affinity Sensing Strategies for the Detection of Pesticides in Food

Abstract

This is a review of recent affinity-based approaches that detect pesticides in food. The importance of the quantification and monitoring of pesticides is firstly discussed, followed by a description of the different approaches reported in the literature. The different sensing approaches are reported according to the different recognition element used: antibodies, aptamers, or molecularly imprinted polymers. Schemes of detection and the main features of the assays are reported and commented upon. The large number of affinity sensors recently developed and tested on real samples demonstrate that this approach is ready to be validated to monitor the amount of pesticides used in food commodities.

Keywords: affinity sensors; aptamers; electrochemical detection; immunosensors; molecularly imprinted polymers; optical detection; pesticides.

Figure 1

Schematic representation of electrochemical and optical non-competitive detection strategies by the use of immunosensors: label free assay (A) and labeled assay (B).

Figure 1

Schematic representation of electrochemical and optical non-competitive detection strategies by the use of immunosensors: label free assay (A) and labeled assay (B).

Figure 2

Schematic representation of electrochemical and optical labeled competitive detection strategies by the use of immunosensors: competition for the antibody among the analyte and the labeled antigen (A); competition for the labeled antibody among the analyte and the antigen (B); competition for the antibody among the analyte and the antigen and detection by the use of a labeled secondary antibody (C).

Figure 3

Schematic representation of detection strategies for an electrochemical aptasensor: label free non-competitive detection by the use of a redox probe (A); labeled competitive detection exploiting the signal generated by the electroactive product of the reaction catalyzed by an enzyme (B). The competition for the aptamer is among the analyte and the labeled complementary oligonucleotide; with the increase of the analyte concentration there is a decrease of the labeled complementary oligonucleotide bound to the aptamer and thus of enzyme and consequently a decrease in the electroactive product signal.

Figure 4

Schematic representation of colorimetric detection strategy employing an aptamer; the strategy is based on the analyte-induced aggregation of AuNPs.

Figure 5

Schematic representation of fluorescence detection strategy employing an aptamer; the strategy is based on the fluorophore fluorescence quenching by the use of a quencher.

Figure 6

Schematic representation of an electrochemical molecular imprinted polymers (MIP) sensor production and detection of the analyte: direct detection and indirect detection by the use of a redox probe.

Figure 7

Schematic representation of optical MIPs production with the main fluorescence-based detection strategies by the use of a fluorophore (A); by the use of a fluorescent functional monomer (B) and exploiting the fluorescence quenching of QDs or CDs (C).