Fiber-optic Atrazine immunosensor

Abstract

Fiber-optic sensors based on the excitation of luminescent chromophores by the evanescent field associated with light guiding in an optical fiber can be used for highly sensitive and selective biochemical affinity assays. Due to the small penetration depth of the evanescent field into the medrium, the generation and detection of luminescence are restricted to the close proximity of the fiber core, i.e., fluorophores in solution beyond the evanescent field will not contribute to the emission signal. Evanescent wave sensors allow the binding of fluorophores to the sensor surface to be monitored in real-time mode. These advantages make this approach especially useful for the determination of substances in complex media, such as blood, river water or soil extracts. An evanescent-wave fiber-optic immunosensor for the detection of the herbicide Atrazine has been developed. In the competitive assay format chosen, fluorescein-labeled and nonlabeled Atrazine in solution compete for the binding sites of anti-Atrazine antibodies immobilized on the surface of the optical fiber. A signal reproducibility of better than 5% within the working range of the sensor (0.5–200 nM Atrazine concentration) is achieved. The sensor performance in complex media has been investigated using samples of surface water and soil extracts.