Fiber-Optic Immunosensors for Detection of Pesticides

Abstract

A reusable fiber optic enzyme biosensor provided rapid detection of acetylcholinesterase (AChE) inhibitors and fast regeneration of the sensor for reuse. However, while highly sensitive in detection of oxyphosphate AChE inhibitors, it was insensitive in detection of the less active thiophosphates. It was generic in its identification and did not identify the chemical structure of the analyte. A fiber optic immunosensor, using polyclonal antiparathion antibodies (Abs) was very selective (could differentiate between parathion and paraoxon) and more sensitive, but too slow and nonreusable. A new strategy was developed, using fluorescent pesticide derivatives and polyclonal or monoclonal Abs to construct reusable biosensors with faster turn around time. An immunosensor was developed to assay for imazethapyr herbicide, that was highly sensitive and selective for imidazolinone compounds, unaffected by soil extract matrix and capable of repeated usage. Advantages of biosensors over ELISA are simplicity, speed and reduced need for sample pretreatment.Immunoassays have been used for years to detect pesticide residues in soil, water and plants. However, the ELISA type assays used are usually time consuming and many of the antibody (Ab) types utilized are either polyclonal or are not highly selective. There is a growing need for assays that are rapid, cost effective and highly sensitive, without giving false negative or false positive results. Two major technological developments are making these objectives within reach. One is in the biosensor field, with advances in a variety of transducers and biological sensing elements, which makes it technically feasible to detect almost any analyte. The other is in the field of molecular immunology, which allows the engineering of an Ab with the exact affinity needed for each pesticide or metabolite of interest, that would provide sensitivity, selectivity and reversibility, and guarantees a stable continuous supply by transfecting the whole or fragments of the Ab gene(s) in E. coli (Ward, 1992).

Environmental applications of analytical biosensors

“…Changes in the absorbance, luminescence, polarization or refractive index are then detected. For more information on fibre optic biosensor design, advantages, limitations and other technical aspects see [2,[52][53][54]. As an example, benzopyrene bound to antibodies immobilized on the distal part of a fibre optic has been detected due to its intrinsic fluorescence when excited by laser radiation (He-Cd) transmitted inside the fibre [55,56].…”

Evanescent Wave Long-Period Fiber Bragg Grating as an Immobilized Antibody Biosensor

“…Detection and quantification of biomolecular interactions have benefited greatly from the incorporation of fiber-optic technology . A variety of optical sensing strategies have been developed, which are capable of detecting a broad range of biologicals including, but not limited to antibodies, , nucleic acids, , toxins, pesticides, , explosives, and numerous other small molecules.…”