A comparative study for evaluating the binding affinity of MARAS-selected aptamer and a patented aptamer towards aflatoxin B1 by electrochemical impedimetric aptasensing

Magnetic-assisted rapid aptamer selection (MARAS) is a technique that uses magnetic nanoparticles to efficiently separate aptamer-target complexes under an alternating magnetic field, thereby reducing the time and number of selection rounds required. This study investigated the applicability of MARAS in selecting aptamers against a small molecule, aflatoxin B1 (AFB1). Among the six MARAS-selected aptamers, DNA 1 demonstrated the highest binding affinity. Its Kd value, further estimated from aptasensing data, was 43.7 nM, which is comparable to the Kd value of the patented aptamer (55.6 nM). The DNA 1-immobilized aptasensor exhibited good repeatability (RSD < 7%, N = 3), linearity (R2 = 0.9613 from 1 to 100 nM), and a calculated LOD of 0.42 nM. Specificity testing indicated that interferences from ochratoxin A, aflatoxin B2, aflatoxin G1, and aflatoxin G2 were all below 7%. The developed aptasensor was also applied to detect AFB1 content in the peanut sample matrix, achieving a good recovery rate ranging from 94.3% to 112.2%. Overall, this study confirms the potential of MARAS as a promising technique for identifying aptamers with strong binding affinities towards low molecular weight compounds such as AFB1. Additionally, the DNA 1-immobilized aptasensor provided a simple, accurate, and cost-effective alternative for AFB1 monitoring.