Highly sensitive electrochemical assay for Nosema bombycis gene DNA PTP1 via conformational switch of DNA nanostructures regulated by H+ from LAMP

The portable and rapid detection of biomolecules via pH meters to monitor the concentration of hydrogen ions (H+) from biological reactions (e.g. loop-mediated isothermal amplification, LAMP) has attracted research interest. However, this assay strategy suffered from inherent drawback of low sensitivity, resulting in great limitations in practical applications. Herein, a novel electrochemical biosensor was constructed for highly sensitive detection of Nosema bombycis gene DNA (PTP1) through transducing chemical stimuli H+ from PTP1-based LAMP into electrochemical output signal of electroactive ferrocene (Fc). With use of target PTP1 as the template, the H+ from LAMP induced the conformational switch of pH-responsive DNA nanostructures (DNA NSs, Fc-Sp@Ts) that was assembled by the hybridization of Fc-labeled signal probe (Fc-Sp) with DNA-based receptor (Ts). Due to the folding of Ts into stable triplex structure at decreased pH, the configuration change of Fc-Sp@Ts led to the releasing of Fc-Sp, which was subsequently immobilized in the electrode interface through the hybridization with the capture probe modified with -SH (SH-Cp), generating amplified electrochemical signal from Fc. The developed biosensor for PTP1 exhibited a reliable linear range of 1 fg µL−1 to 50 ng µL−1 with the limit of detection of 0.31 fg µL−1. Thus, by the regulation of H+ from LAMP reaction on DNA NSs allostery, this novel and simple transduction scheme would be interesting and promising to open up a novel analytical route for sensitive monitoring of different target DNAs in related disease diagnosis.