LAMP-CRISPR/Cas12a-based impedimetric biosensor powered by Fe₃O₄@Au-(S-polyA-S)-Au for detection of SARS-CoV-2

A low-cost, lab-made polytetrafluoroethylene micro-cell, equipped with three electrodes, wasd eveloped for the impedimetric detection of SARS-CoV-2. The gold working electrode was modified with a double-ended thiolated poly-adenine probe, which was conjugated with magnetic Fe₃O₄@Au nanoparticles (Fe₃O₄@Au-(S-polyA-S)-Au). After the loop-mediated isothermal amplification (LAMP) of viral RNA, the single-guide RNA (sgRNA), specifically bound to the SARS-CoV-2 target sequence, activates Cas12a. Cas12a then cleaved the immobilized probe. As a result, the magnetic Fe₃O₄@Au nanoparticles were released and adsorbed onto the gold electrode surface, using an external magnet. This process increased the physical surface area of the gold electrode, facilitating redox ion ([Fe^III/II(CN)₆]^3−/4−) electron transfer. The decrease in the charge transfer resistance was utilized for SARS-CoV-2 detection. Our LAMP-CRISPR/Cas12a-based impedimetric biosensor, powered by Fe₃O₄@Au-(S-polyA-S)-Au, demonstrated impressive capabilities, including a remarkable detection limit of 0.8 aM (0.48 copies/µL) and a linear range of 0.01 to 36.06 fM.