A high-sensitivity magnetic-controlled separable visuable aptasensor based on neutral pH SOD-like dual-metal based...

Aflatoxin B1 (AFB1), a highly toxic and stable mycotoxin, endangers food safety and public health. Current aptamer-nanozyme detection systems often require acidic conditions (pH 3.0-5.5), impairing aptamer-target binding. Here, we developed a neutral-pH colorimetric aptasensor using a biomimetic superoxide dismutase (SOD)-like nanozyme. A bimetallic Mn/Cu-MOF was synthesized via a MOF-on-MOF strategy, combining a Cu-MOF core with a hydroxyl-rich Mn-MOF shell to mimic natural SOD's catalytic centers and hydrogen-bonding microenvironment. The aptasensor employs AFB1-specific aptamers immobilized on magnetic nanoparticles (Apt@Fe₃O₄) and cDNA-conjugated Mn/Cu-MOF (cDNA@Mn/Cu-MOF). Target binding displaces cDNA@Mn/Cu-MOF, enabling its SOD-like catalytic reduction of nitro blue tetrazolium (NBT) under neutral pH. The absorbance at 560 nm correlates linearly with AFB1 concentration (0.1-3000 ng/mL), achieving a 0.07 ng/mL detection limit. Recoveries in spiked peanut samples ranged from 91.80 % to 109.08 %. This strategy offers sensitive AFB1 detection and a novel neutral-pH biosensor design paradigm.