Subnanomolar detection of ochratoxin A using aptamer-attached silver nanoparticles and surface-enhanced Raman scattering

We report a new approach for the detection of ochratoxin A (OTA) by introducing surface-enhanced Raman scattering (SERS). This method is based on different adsorption propensities of Raman reporter Cy5-tagged OTA aptamer. The OTA aptamer could be easily adsorbed onto the surface of silver nanoparticles (AgNPs) to give fairly strong SERS signals, whereas such bindings would be hampered in the presence of OTA. On the addition of OTA in the concentration range of 0.1-10 nM, the SERS signals appeared to decrease by similar to 40%, since OTA's aptamer could not adsorb onto the surface of AgNPs due to binding with OTA. We verified our results against a control experiment with warfarin, which did not affect the SERS signals. A nanomolar detection limit of OTA was achieved using the current SERS-based method.