A photothermal aptasensor based on rolling circle amplification-enriched DNAzyme for portable detection of ochratoxin A in grape juice

Aptasensors for detection of ochratoxin A (OTA) have been extensively studied, but the majority of them require costly and large-scale equipment as signal readers. Herein, a photothermal aptasensor capable of portable detection of OTA through a thermometer was developed on basis of aptamer structural switching and rolling circle amplification (RCA)-enriched DNAzyme. Oligonucleotides and alkaline phosphatase (ALP) modified magnetic beads were prepared. The binding of aptamers to OTA led to the release of ALP labeled complementary DNA. After magnetic separation, ALP catalyzed the padlock dephosphorylation, inhibiting the subsequent RCA reaction. This process converted the OTA concentration into the amount of the photothermal reagent oxTMB produced from the catalytic reaction induced by RCA-enriched DNAzyme. Under the optimal conditions, the detection limit (LOD) of this aptasensor was 2.28 nM in a clean buffer, while the LOD reached 2.43 nM in 2 % grape juice. The good performance of the photothermal aptasensor makes it possible to measure OTA pollution in low resource environments.