A fluorescence and surface-enhanced Raman scattering dual-mode aptasensor for rapid and sensitive detection of ochratoxin A.

A fluorescence and surface-enhanced Raman scattering (FL-SERS) dual-mode aptasensor was established for sensitive and rapid detection of Ochratoxin A (OTA). This aptasensor was assembled by the hybridization of OTA aptamer (OTA Apt) modified gold nanostars (Apt-AuNSs) and Cy3 modified complementary DNA functionalized gold nanospheres (cDNA-AuNPs). The aptasensor displays a low FL signal due to the proximity of Cy3 to AuNSs, and a high SERS signal due to the "hot spot" effect generated by the nano-gap between AuNSs and AuNPs. In the presence of OTA, the preferential combination of OTA Apt and OTA results in a low SERS signal. Meanwhile, cDNA-AuNPs are released from the hybrid complex, leading to the recovery of the FL signal. The aptasensor has a low detection limit of 0.17 ng/mL (the detection range is 1-100 ng/mL) in FL mode and 1.03 pg/mL (the detection range is 5-250 pg/mL) in SERS mode. Furthermore, this aptasensor exhibits high specificity and good interferent resistance, which can discriminate OTA from other mycotoxins. Moreover, this aptasensor can be used for OTA detection in coffee and wine samples with good recovery rates. Unlike single-signal aptasensors, this dual-mode aptasensor holds exquisite properties such as high reliability, great detection flexibility and good anti-interference ability.