Pollen-stigma biomimetic framework: a CuCo2O4 nanozyme-based electrochemical aptasensor for ultrasensitive aflatoxin B1 detection.

Inspired by the highly specific recognition and signal amplification of pollen germination on a stigma, we propose a biomimetic electrochemical sensing strategy for ultrasensitive aflatoxin B1 (AFB1) detection. In this pollen-mimetic system, CuCo2O4 nanoflowers serve as "pollen-mimetic grains", with their bimetallic Cu/Co centers functioning as an internal "energy conversion system" for robust signal output. AFB1 acts as the "stigmatic secretion", triggering the release of CuCo2O4 nanoprobes from the aptamer complex via target-induced strand displacement. The released nanoprobes are subsequently captured by a hairpin probe on the electrode, which mimics the "stigmatic receptor", through specific DNA hybridization. Finally, the captured CuCo2O4 nanozyme catalyzes the oxidation of TMB, mimicking "pollen germination and tube growth" to amplify the recognition event into a measurable electrochemical signal. Under optimized conditions, this biomimetic sensor achieves a wide linear range (10-11 to 10-4 mg mL-1) and an ultralow detection limit of 2.59 fg mL-1, with excellent reproducibility, stability, and selectivity. Recovery rates in real food samples range from 97.61% to 101.53%. This pollen-stigma biomimetic framework not only provides a highly sensitive platform for AFB1 detection but also establishes a new paradigm for designing high signal-to-noise ratio biosensors for complex matrices.