New ways in bioanalysis - one-way optical sensor chip for environmental analysis

An optical immunosensor system consisting of a disposable low-cost sensor c hip including a fluidic system and a base unit for optical readout was deve loped. Near infrared (NIR)-fluorescence markers (Cy5) were excited by an ev anescent wave generated on the surface of the sensor chip. The combination of both fluorescence measurements and evanescent wave excitation provides e xtremely sensitive detection and avoids any washing or separation steps. To demonstrate the feasibility of the system for environmental control assays for the determination of the herbicide 2,4-dichlorophenoxyacetic acid (2,4 -D) were developed. Two different assay formats were applied to determine 2 ,4-D in the relevant concentration range. Due to the assay formats chosen a direct proportional relationship between analyte concentration and signal intensity was achieved. Within an assay time of 15 min only, the analyte 2, 4-D could be determined in a linear concentration range covering three orde rs of magnitude. (C) 1998 Elsevier Science S.A. All rights reserved.