An ultrasensitive electrochemical sensing method for detection of microcystin-LR based on infinity-shaped DNA structure using double aptamer and terminal deoxynucleotidyl transferase.

This study develops a novel electrochemical sensing platform for microcystin-LR (MC-LR) detection. This aptasensor comprises the hybridization of double aptamer to its complementary strand (CS) on the surface of electrode and generation of an Infinity-shaped DNA structure in the absence of target by terminal deoxynucleotidyl transferase (TdT). The formation of Infinity-shaped construction leads to the development of an ultrasensitive aptasensor for MC-LR detection. In the presence of MC-LR, double aptamer is dissociated from its CS because of its high affinity for MC-LR and leaves the surface of electrode. Subsequently, no Infinity-shaped structure is formed following the introduction of TdT and a strong current signal is observed. The proposed method was employed for specific detection of MC-LR in the range from 60 pM to 1000 nM with a detection limit of 15 pM. The credibility of the approach was confirmed by detection of MC-LR in real samples like serum and tap water samples. This study provides a new aptasensor for detection of MC-LR as well as other toxin analysis.