An Electrochemical Aptasensor with Enhanced Electrocatalytic Signal by Electrode Modification Material for Aflatoxin B1 Detection-Based Bipedal DNAzyme Cleavage Effect

Designing an electrochemical aptasensor for detecting Aflatoxin B1 (AFB₁) in food samples is a great challenge. Herein, a catalytic hairpin assembly combined with a bipedal Mg²⁺-dependent deoxyribonuclease (Mg²⁺-DNAzyme) serves as a signal enhancer. Polyethylenimine-Ce-based metal-organic framework@nitrogen-doped multiwalled carbon nanotubes/gold nanoparticles nanocomposites (P-CeMOFs@MWCNTs/AuNPs) were used as electrode modification materials, and MOF-derived Co₃O₄ and AuNP-labeled oligonucleotides (Au@Co₃O₄@S) served as signal probes. An ultrasensitive electrochemical aptasensor for the detection of AFB₁ was developed. During the reaction, AFB₁ displaced the aptamer from the complementary chain (T), enabling formation of the HP1-HP2 complex by opening HP1 and binding to HP2. HP3, containing ribonucleotide (rA), was repeatedly cleaved in the presence of Mg²⁺, thereby vacating the complementary chain to capture the Au@Co₃O₄@S signal probe, ultimately leading to signal amplification. With such a design, the detection range of the sensor was verified to be 1 × 10^-4-1 × 10² ng/mL, and the limit of detection was 6.3 × 10^-5 ng/mL. Under optimal conditions, the aptasensor had excellent specificity, reproducibility, and stability, while the recovery in food samples made it eligible for a wide range of applications.