Selection of azaspiracid-1 aptamers for potentiometric aptasensing

Azaspiracids (AZAs) are polyether marine toxins from shellfish that cause risks to human health. The bioreceptors for biosensing of AZAs are limited to antibodies. The selection of aptamers that specifically bind to AZAs with high affinities is highly required. In this work, aptamers with high affinities and specificities towards AZA1, which is the most abundant toxin in the AZAs group, have been selected via the magnetic reduced graphene oxide-based systematic evolution of ligands by exponential enrichment (MRGO-SELEX). A truncated aptamer (Apt-23b48) with a dissociation constant (K_d) of 29.8 ± 8.3 nM has been chosen as a bioreceptor for fabricating DNA self-assembled nanostructure-based magnetic beads via a hybridization chain reaction. A polycation-sensitive thin-membrane electrode using protamine as an indicator has been employed to detect the surface charge change of the DNA self-assembled nanostructure-based magnetic beads induced by the binding interaction between the selected aptamer and AZA1. The proposed potentiometric aptasensing platform shows a linear range of 10-250 pM with a detection limit of 8.5 pM, and has been successfully applied to the detection of AZA1 in spike seawater samples.