An ultrasensitive competitive label-free electrochemical immunoassay platform based on Cu-based MOF-derived architecture for aflatoxin B1 detection

In this study, we developed an ultrasensitive competitive label-free electrochemical immunoassay for the detection of aflatoxin B1 (AFB1) based on a Cu/Cu 2 O/C nanocomposite platform. The sensing matrix was fabricated by thermal decomposition of a two-dimensional copper-organic framework, inheriting the porous structure and large surface area characteristic of MOFs while exhibiting enhanced electrical conductivity. In this competitive detection scheme, free AFB1 molecules compete with electrode-bound AFB1-BSA conjugates for limited antibody binding sites. The resulting variation in electrochemical signals exhibits an inverse correlation with toxin concentration, facilitating ultra-trace detection with an impressive limit of detection of 1.83 pg/mL. The immunosensor features dual linear detection ranges of 10–100 pg/mL and 150–1000 pg/mL, with high specificity and reproducibility. It responds significantly to AFB1, showing minimal cross-reactivity with AFB2 and AFG1, and negligible responses to unrelated mycotoxins. Reproducibility testing yielded an RSD of less than 0.2 %. The sensor retains over 95 % of its initial response after seven days at 4 °C, indicating stability. Validation with spiked cornstarch samples showed recovery rates of 99.68 % to 104.38 % and an RSD of less than 4 %, confirming its effectiveness in real sample analysis. This study establishes a generalizable approach for constructing high-performance immunosensing platforms that are applicable to various mycotoxins and biological targets.