A highly sensitive electrochemical aptasensor for detection of microcystin-LR based on a dual signal amplification strategy

Abstract

In this work, a sensitive and selective electrochemical aptasensor for determination of microcystin-LR (MC-LR) was developed based on a dual signal amplification system consisting of a novel ternary composite and horseradish peroxidase (HRP). The ternary composite was prepared by depositing gold nanoparticles (AuNPs) on molybdenum disulfide (MoS₂) covered TiO₂ nanobeads (TiONBs). MoS₂ nanosheet modified TiONBs provided a large surface area for immobilization of AuNPs and biomolecules. The ternary composite also possesses an improved electron transfer and catalytic capability. To construct the aptasensor, thiolated MC-LR aptamers were immobilized on the AuNP@MoS₂-TiONB modified electrode through a gold–sulfur bond. Then, biotin–cDNA with a sequence complementary to the MC-LR aptamer competed with MC-LR for binding to the immobilized aptamer. The current signal catalyzed by avidin–HRP decreased with the increase of MC-LR, based on which a linear range of 0.005–30 nM and a detection limit of 0.002 nM were obtained.