Development of a colorimetric aptasensor fabricated with a group-specific aptamer and AuNPs@Fe2+ nanozyme for simultaneous detection of multiple diarrheic shellfish poisons

Okadaic acid (OA), dinophysistoxin-1 (DTX-1), and dinophysistoxin-2 (DTX-2) are the main diarrheic shellfish poisons (DSPs). Detection methods to achieve simultaneous detection of the three toxins are urgently needed. In this paper, a terminal fixation design proposed in our previous study was further explored to engineer an aptamer with group-specific recognition ability from an original aptamer binding to one target. Both molecular docking assay and biolayer interferometry assay were applied to reveal the binding mechanisms between three DSPs and the engineered aptamer. Then, a label-free colorimetric aptasensor by fabricating the aptamer with AuNPs@Fe2+ nanozyme was constructed, which provided a wide linear detection range (0.4688-7.5 nM), a very low limit of detection (LOD, 86.28 pM), and good recoveries (96.02-104.9%) when analyzing DSPs in seawater and scallop samples, indicating the engineered aptamer and the developed aptasensor had great potential in recognizing and detecting multiple DSPs in real world.