A Fiber-Optic Immunosensor for Detecting Parathion

Casein-parathion conjugates, immobilized by adsorption on quartz fibers, selectively adsorbed antiparathion rabbit antibodies raised against bovine serum albumin (BSA)-parathion conjugates from polyclonal immune sera. The presence of free parathion interfered with binding of the rabbit's antiparathion Abs. Fluorescein isothiocyanate(FITC) goat antirabbit IgG were used to generate an optical signal, which was measured by a signal transducer based on total internal reflection fluorescence. Inhibition of binding of rabbit Abs by free parathion, reduced the optical signal and provided the basis for detection of parathion with this optical immununosensor. It could detect 0.3 ppb parathion and was highly specific since its detection of the oxygen analog paraoxon was possible at 100-fold higher concentration.