Integrated optical immunosensor for s-triazine determination: regeneration, calibration and limitations

Abstract

Grating couplers, as an example of an integrated optical transducer, were investigated for label-free immunosensing in a flow-through system. The detection of pesticides by a competitive assay format was demonstrated using a triazine (terbutryn) as an example. Long-term stability and reproducibility were achieved by immobilizing the hapten, which in this instance was a derivative of the pesticide to be determined. Hence, the lifetime of the sensor does not depend on the stability of the antibody but is limited only by the quality of the immobilization. Regeneration of the sensor surface was achieved using proteinase supported by acidic washing; it was observed directly and could therefore be optimized. In consequence, calibration, usually critical in immunosensing, was possible. Non-specific binding was determined to be 10% and could be decreased by addition of bovine serum albumin. The detection limit found for terbutryn was 15 µg l^–1 in the arrangement used; strategies for enhancement of sensitivity are discussed.