NiCo2S4 nanoparticle-dispersed MoS2 nanosheets for catalytic and sensitive electrochemical aptamer sensing of ochratoxin A via cascaded amplifications

Abstract

Highly sensitive monitoring of mycotoxins is of major importance for food safety and human health. In this work, on the basis of a new catalytic sensing interface of NiCo2S4 nanoparticle-dispersed MoS2 nanosheet (NiCo2S4 @MoS2)-modified electrode and the signal amplifications by 3D DNA walker and hybridization chain reaction (HCR), a sensitive electrochemical aptamer sensor for the detection of ochratoxin A (OTA), one of the most toxic mycotoxin widely distributed in food, is developed. The synthesized NiCo2S4@MoS2 shows enhanced catalytic current responses toward the methylene blue (MB) signal tag. The presence OTA results in the activation of the DNA walker to cyclically cleave the hairpin substrate DNAs to release many triggering sequences for the initiation of HCR between two hairpins, leading to the attachment of numerous MB-labeled strands on the sensor electrode. Subsequent electrocatalytic oxidation of MB thus yields drastically enhanced current responses for highly sensitive sensing of OTA with the detection limit of 0.42 pg mL−1 in the dynamic range of 0.5 pg mL−1-1 ng mL−1. Moreover, this sensing platform exhibits high selectivity and can be applied to monitor OTA spiked in real samples, showing its potential for the development of robust aptamer sensors for various mycotoxins.