An ultrasensitive electrochemical aptasensor for microcystin-LR detection using core-satellite gold nanoparticle/silver nanocluster nanoassemblies as labels for signal amplification

Abstract

In this work, an ultrasensitive electrochemical aptasensor for microcystin-LR (MC-LR) detection had been developed using core-satellite gold nanopaticle/silver nanocluster nanoassemblies (sDNA-AuNP@AgNC) as electrochemical labels. sDNA-AuNP@AgNC was characterized by transmission electron microscopy, and X-ray diffraction and ultraviolet-visible absorption spectroscopies. Functional cytosine-rich single-stranded DNA (sDNA) integrating both template sequence and recognition sequence for hybridization was immobilized on AuNP surface through Au-S bond to prepare AuNP conjugations (sDNA-AuNP). After hybridization of sDNA-AuNP and incubation of AgNO3 solution, generous Ag+ ions were encapsulated into sDNA-AuNP at electrode by the strong C-Ag+-C structure. AgNC was in situ synthesized on sDNA-AuNP to form core-satellite sDNA-AuNP@AgNC nanoassemblies, which showed enhanced electrocatalytic performance toward H2O2 reduction and produced a detection signal on aptasensor surface. In the presence of MC-LR, MC-LR aptamer preferentially bound to MC-LR, and the electrochemical signal decreased. A competitive aptasensing assay was used in our work, and the efficient signal amplification of sDNA-AuNP@AgNC made the MC-LR aptasensor have a low detection limit of 0.06 pM (S/N = 3) and a wide linear range from 0.2 pM to 200 nM. This designed aptasensor showed excellent selectivity, reproducibility and stability, and had been applied to detect MC-LR concentration in real samples.