Label- and wash-free electrochemical nucleic acid detection via a LAMP platform coupled with silver ion aptamer...

We present a novel electrochemical nucleic acid detection strategy based on loop-mediated isothermal amplification (LAMP) coupled with silver ion (Ag⁺) aptamer probes. The strategy employs specially designed hairpin-shaped probes comprising an Ag⁺-binding aptamer sequence in the stem region and a target-complementary sequence in the loop region. In the presence of the target nucleic acid, the LAMP reaction is initiated, and the resulting amplicons hybridize with the loop region of the probe. This interaction disrupts the hairpin structure, leading to the release of Ag⁺ from the stem region. The liberated Ag⁺ subsequently participates in a redox reaction at the electrode surface, producing an enhanced electrochemical signal proportional to the amount of LAMP amplicons. Using this approach, we achieved highly sensitive detection of the vanA gene from the genomic DNA of Enterococcus faecium, a key marker of vancomycin-resistant Enterococci, with a detection limit of 10 copies in a 50 μL reaction volume within 45 min from amplification to electrochemical detection, while maintaining high specificity. Owing to its label-free, wash-free, and one-step detection capability, this strategy shows strong potential as a practical platform for electrochemical molecular diagnostics in point-of-care settings.