DNA aptamer selection and detection of marine biotoxin 20 Methyl Spirolide G

•DNA aptamers were generated against 20 Methyl Spirolide G (SPX G) using SELEX.•All selected aptamers showed affinity for SPX G with appreciable binding affinity.•Aptamer SPX7 had binding affinity in the nanomolar range against the toxin.•A MST-based label-free aptasensor using SPX7 was developed for SPX G detection.•The aptasensor showed a LOD of 0.39 pg/mL and LOQ of 1.17 pg/mL. This study reports the selection of DNA aptamer for the detection of 20 Methyl Spirolide G (SPXG). After 10 rounds of selection, theenriched pool of aptamers specific to SPXGwas cloned, sequenced and clustered into seven families based onsimilarity. Three sequences SPX1, SPX2 and SPX7, each belonging to different clades were further evaluated for their binding affinity. Surface plasmonresonancestudies determined the highest affinity KDof 0.0345x10-8 M for aptamer SPX7. A label-free microscale thermophoresis-based aptasensing using SPX7 with highest affinity, indicated a linear detection range from 1.9 to 125000 pg/mL (LOD = 0.39 pg/mL; LOQ = 1.17 pg/mL). Spiking studies in simulated contaminated samples of mussel and scallop indicated recoveries in the range of 86 to 108%. Results of this study indicate the successful development of an aptamer for detection of SPXG at picogram levels. It also opens up avenues to develop other sensing platforms for detection of SPXG using the reported aptamer.