From Leuco to Blue: Photochemical Redox Amplification for Small-Molecule Immunodetection

-independent pathways; red light is then used to excite nascent MB to drive a secondary photocatalytic reductive cycle that regenerates MB through radical/anionic intermediates, yielding exponential signal growth. We have validated immunoassay integration using ZON-specific monoclonal antibodies in bead-based and plate formats, demonstrating specific, light-triggered fluorescence that reports competitive binding. Its implementation with sequential two-color illumination demonstrates selective system activation and precise control of the signal amplification (300-fold). This photochemical approach provides stable, long-term reagents that can be tailored to the target species and offers a potentially general strategy for developing enzyme-free, high sensitivity immunoassays for small analytes.