Optic fiber sensors with tunable sensitivities for rapid detection of amatoxins in water and mushroom derived agro-products

Amatoxin is a toxin predominantly found in Amanita phalloides, popularly called 'the death cap mushroom'. An optical fiber-based biosensor has been developed for the detection of amatoxin in water and mushroom derived agro-products. In the first configuration, U-bend optical fibers modified with spherical gold nanoparticles (SGnP) were used for localised surface plasmon resonance (LSPR) based immunosensing of amatoxin in deionised water, and in mushroom based agro-products. The sensor was calibrated for a range of 0.5-200 µg/mL in water, 1-200 µg/mL in mushroom, and 0.1-100 µg/mL in mushroom wine with a detection limit of 0.5,1, and 0.1 µg/mL respectively. To further tune the sensitivities, a gold-on-gold approach was devised where gold nanorods (GnR) were immobilized on SGnP modified fibers to attain higher plasmonic field and penetration depth. These sensors were calibrated for a range of 0.001-10 µg/mL in water, and 0.01-10 µg/mL in mushroom and was able to detect the toxin within 30 min. The sensor performance was validated with real mushroom samples characterized to inherently contain amatoxin by HR-LCMS; and a coherent value of 1.41 ± 0.27 µg/mL was obtained by sensors developed with both approaches. Recovery studies with mushroom tinctures and mushroom samples indicated an overall error of <10 % with respect to the standard calibrations. Thus, a technique to tailor the sensitivities of optic fiber based LSPR immunosensors to achieve sensing in relevant ranges is demonstrated, which will be pertinent in screening of amatoxins in water, and mushroom derived agro-products, to decide on its fitness for consumption.