Dual-mode electrochemical/colorimetric microfluidic sensor integrated tetrahedral DNA nanostructures with Au/Ni-Co LDH NCs nanozyme for ultrasensitive detection of aflatoxin B1

Aflatoxin B1 (AFB1) is one of the most hazardous mycotoxins and lead to a deadly danger to animal and human health. The development of portable, low-cost, and easy to operate analytical tools is essential for AFB1 detection, especially in resource-limited regions. Herein, a dual-mode microfluidic paper-based analytical device (μPAD) with electrochemical and colorimetric readout was constructed for AFB1 detection using Au NPs anchored Ni-Co layered double hydroxides nanocages (Au/Ni-Co LDH NCs) as a signal amplifier. In this design, tetrahedral DNA nanostructures (TDNs) were employed as a scaffold to anchor "bottom-up" aptamers (Apt) for improving capture efficiency of AFB1. Au/Ni-Co LDH NCs with excellent peroxidase (POD)-like activity were bound on the TDNs through hybridization of Apt and complementary DNA (cDNA), a significant electrochemical signal of H2O2 reduction was generated. Meanwhile, the·OH from H2O2 decomposition catalyzed the oxidation of 3,3′,5,5′-tetramethylbenzidine and resulted in a colorimetric signal. The binding of target AFB1 to Apt triggered the dissociation of Apt/cDNA, causing the release of the signal amplifier from the sensing interface and signal decrease. Consequently, a detection range of 0.2 pg/mL-100 ng/mL for electrochemical and 50 pg/mL-100 ng/mL for colorimetric were achieved for AFB1, holding promising application in the fields of food safety.