Sensitivity enhancement of transducers for total internal reflection fluorescence

We have developed, modeled and optimized optical transducers for total internal reflection fluorescence (TIRF). The transducers are part of a compact and rugged immuno-analytical instrument designed for simultaneous detection of up to six analytes in aquatic samples (e.g. atrazine and 2,4-D). Binding inhibition assays, using Cy5.5 labeled antibodies to detect the target analytes, have been carried out. Calibration curves with mid-points of tests below 1 (mu) g/1 and detection limits below 0.1 (mu) g/1 have been achieved. As transducer either ion exchanged integrated optical channel waveguides or planar multimode slab waveguides have been employed. The transducer performance was significantly enhanced by incorporating thin high index films at the waveguide surface and by applying high refractive index solutions in the superstrate. Peak signal enhancement factors of more than ten have been observed and an increase in signal to noise ratio by a factor of more than four have been achieved. Strong polarization dependent effects on the enhancement by high index films have been found both theoretically and experimentally.