Optical methods based on recording a phase shift of electromagnetic waves offer high sensitivity for detection of bio-reactions. The method of Total Internal Reflection Ellipsometry (TIRE), which records simultaneously two parameters Ψ and ∆ related, respectively, to the amplitudes and phases of p-and s-components of polarized light, was exploited here for detection of mycotoxins (T-2, zearalanone, and aflatoxin). The TIRE direct label-free immunoassay enables detecting the above mycotoxins in sub-ppb concentrations in water as well as in food extracts. Further enhancement of sensitivity can be achieved with the use of SiO 2 /Si 3 N 4 /SiO 2 planar waveguides operating as polarization interferometers (PI).
The method of spectroscopic ellipsometry in total internal reflection mode (TIRE) was utilised for detection of Aflatoxin B1. The method of TIRE with the improved data analysis was capable of detection of aflatoxin molecules in low concentrations (down to 0.04 ng/ml) using a label-free and cost-effective direct immunoassay format. TIRE study of the binding kinetics yielded a large value of the association constant in the range of 10 6 l mol −1 which is typical for highly specific immune reactions. The comparison of the experimental data for three mycotoxins studied (e.g. aflatoxin B1, T-2 mycotoxin, and zearalenone) confirmed a common mechanism of the sensitivity boost due to the aggregation of hydrophobic molecules of mycotoxins in aqueous solutions.
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