All-DNA self-assembled G-Quadruplex/hemin DNAzyme nanosphere for ultrasensitive electrochemical detection of kanamycin residue

Herein, we propose an all-DNA self-assembled G-quadruplex/hemin DNAzyme nanosphere (GHN) and apply it to construct an electrochemical biosensor for sensitive detection of kanamycin (KAN). Unlike conventional metal-core-dependent biosensors, the GHN eliminates inorganic components, offering superior biocompatibility, simplified synthesis, and reduced environmental hazards. High loading of G-rich sequences was achieved by performing multiple branches of the hybridization chain reaction on self-assembled DNA spherical core. In addition to exhibiting excellent catalytic performance, the GHN inherently provides a strong current response, facilitating highly sensitive detection of target analytes. Through a one-step displacement reaction triggered by the target, the GHN is captured on the electrode surface, generating a measurable current signal. Under optimal experimental conditions, the electrochemical signal of the proposed sensor showed a good linear relationship with the logarithm of the KAN concentration over the range of 0.1 pM to 1   μM, with a detection limit of 71 fM (S/N = 3). For practical applications, the sensor achieved 93.98% to 102.0% recovery in spiked milk samples, demonstrating its reliability in complex matrices. The target-independent synthesis of GHN allows facile reconfiguration by altering aptamer sequences, enabling universal detection of environmental pollutants and biomarkers. This platform offers a new approach for early monitoring of antibiotic residues, which is expected to provide valuable references for the formulation of relevant environmental protection policies and the safeguarding of human health.