An evanescent wave multi-channel immunosensor system for the highly sensitive detection of small analytes in water samples

• An evanescent wave multi-channel immunosensors (EWMI) system is proposed.
• A reusable biosensing surface is established on the optical waveguide chip.
• EWMIs provide a universal platform for other small analytes.
• EWMIs pave the way for the multi-analytes sensing up to eight indicators.

To simultaneously detect multiple analytes in water samples, we propose an integrated evanescent wave multi-channel immunosensor (EWMI) system. This system employs fluorescence-based detection of the binding of fluorophore-tagged antibodies to the surface of a planar optical waveguide chip. Incident light is coupled into the planar optical waveguide chip via a beveled angle to form eight individual reflection spots for multi-analyte biosensing. Fluorescence emissions are collected by eight multi-mode fibers placed in parallel underneath the chip. A reusable biosensing surface is established via the covalent attachment of the analyte derivative onto the optical waveguide chip. With one spot for 2,4-dichlorophenoxyacetic acid (2,4-D) detection taken as an example, the pre-incubation time, antibody concentration, and incubation time of EWMI system are optimized. 2,4-D, microcystin-LR, bisphenol A, and melamine are simultaneously and specifically detected within an analysis time of about 20 min for each assay cycle. The regeneration of the planar optical waveguide chip allows more than 300 assay cycles.

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