In this study, a simple electrochemical aptasensor for saxitoxin (STX) detection was developed based on a short anti-STX aptamer with a methylene blue (MB) incorporated at the 3'-end. The aptamer was immobilized on the surface of gold electrode and served as the recognition element. The aptasensor was successfully used as a highly selective and sensitive biosensor for STX detection because of the selection of aptamer along with the excellent electrocatalytical properties of MB. With the increase of the dynamic concentration of STX from 1 nM to 1 μM, the aptasensor exhibited a sensitivity with a peak current change of 2.92 μA per decade and a low detection limit of 1 nM. In addition, the aptasensor demonstrated excellent selectivity to STX, which prevented the interferences from neo-STX, okadaic acid and common metal ions. Using the proposed principle, several other aptasensors with improved performance can be constructed via the modification of the electrochemical sensor with appropriate aptamers.
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