A novel MB-tagged aptasensor for Aflatoxin B1 detection in food using Fe3O4 nanoparticles substantiated with in silico modelling

Aspergillus fungi species found in wheat, maize, rice, and other agricultural products produce the carcinogenic mycotoxin known as Aflatoxin B1 (AFB1), which can cause cancer in animals and humans. Consequently, recent interest has surged regarding the need for inexpensive, selective, and sensitive sensors to detect AFB1 in food. An ultrasensitive electrochemical aptasensor for AFB1 analysis was constructed using carboxylated multiwalled carbon nanotubes (cMWCNTs) and iron oxide (Fe₃O₄) nanoparticles (NP) on a glassy carbon electrode (GCE). The peptide bond formation by EDC coupling between the aptamer and cMWCNTs-Fe₃O₄ NP composite exhibited a strong anodic redox response from AFB1 using cyclic voltammetry (CV) in this study. Applying differential pulse voltammetry (DPV), the GCE/cMWCNTs-Fe₃O₄ NP aptasensor exhibited very low limits of detection (LOD) and quantification (LOQ) of 0.43 fg mL⁻¹ and 1.44 fg mL⁻¹ respectively over a calibration ranging from 0.50 fg mL⁻¹ to 5.00 fg mL⁻¹. For actual sample analysis, excellent spike recoveries from 95 to 105% were obtained for corn and rice flour. Single particle ICP-MS (spICP-MS) confirmed the average mass-based diameter of the synthesized Fe₃O₄ NPs to be in the nano-range (d $\approx$ 20 nm), the properties of which are essential for the facilitation of strong electron transfer in DPV sensing. Finally, density functional theory and molecular docking studies predicted the sensing mechanism and supported deductions based on the AFB1 capture by the employed aptamer respectively. As part of South Africa’s quality control and regulatory frameworks, this study aims to contribute toward the prevention of AFB1 exposure in foods.