A Label-Free Electrochemical Aptamer Sensor Based on PEI-CeO2@Pt and PEI-MCA for Detection of Fumonisin B1

Fumonisin B1 (FB1) is a secondary metabolite generated by Fusarium verticillioides, which can widely contaminate crops. Herein, an electrochemical aptamer sensor with high sensitivity and selectivity was constructed for FB1 detection, leveraging the specific recognition capability of aptamers. Polyethylenimine-functionalized cerium dioxide-supported platinum nanoparticles (PEI-CeO₂@PtNPs) were used for the modification of electrodes. The nanocomposite enhanced electrical conductivity on the electrode, and provided more attachment sites to increase the loading capacity of aptamer chains. Additionally, polyethylenimine-functionalized melamine-cyanuric acid condensation polymers (PEI-MCA) were used as carrier for the signal probe. Because of the unique porous structure and abundant functional groups on the surface of MCA, the loading efficiency of methylene blue (MB) was significantly enhanced, and the complementary DNA (cDNA) strand of aptamers was effectively loaded on PEI-MCA by strong electrostatic interaction to construct signal probes. The cDNA was captured by aptamers through complementary base pairing, and PEI-CeO₂@PtNPs amplified electrical responses cooperatively with PEI-MCA. In the presence of FB1, the aptamers preferentially bound to FB1, and the signal probes were detached from the electrode surface, resulting in a decrease in the electrochemical response. Under optimal conditions, the dynamic range of the constructed aptasensor was 1 × 10⁻¹ to 1 × 10⁴ pg/mL, with a detection limit of 89 fg/mL. Additionally, the sensor had high selectivity, reproducibility, and stability, and could detect FB1 in milk and corn flour samples.