Scheme 1.

Illustration of the sandwich immunoassay on a functionalized waveguide. A) Waveguides functionalized with a lipid bilayer are prepared by binding of capture antibody using biotin-streptavidin chemistry. B) Addition of the sample containing the antigen results in specific binding. C) Finally, addition of a fluorescently labeled reporter antibody results in a specific signal measured via a spectrometer interface. Schematic not drawn to scale, and represents process for all three biomarkers investigated in this report.