An electrochemical-fluorescence dual-mode biosensor enabled by a self-protected circular DNAzyme walker for kanamycin...

Sensitive and reliable detection of kanamycin (KAN) in complex matrices remains a significant challenge. Herein, we report an electrochemical-fluorescence dual-mode biosensor that synergistically integrates the high-specificity recognition capability of an aptamer with the robust signal amplification performance of a gold nanoparticle-based three-dimensional self-protected circular DNAzyme walker. KAN can be converted into a single-stranded DNA signal (R) via the KAN recognition probe (Apt/R). Then, the strand R hybridizes with the circular shielding domain containing the catalytic strand of the DNAzyme and activates the DNAzyme walker, thus cleaving methylene blue (MB)-embedded G-quadruplex substrates, leading to simultaneous fluorescence recovery and electrochemical signal amplification. The proposed dual-mode biosensor demonstrates high sensitivity with detection limits of 0.018 fM in the electrochemical mode and 0.327 pM in the fluorescence mode. Moreover, the excellent selectivity and biostability enable the proposed biosensor to specifically discriminate KAN in complex real samples, and the fluorescence mode further allows in situ imaging of KAN in living cells.