Base mismatching-fueled highly efficient catalytic hairpin assembly to regulate Ag nanoclusters brightness for amplifiable fluorescence biosensor

Exploring base mismatching-fueled catalytic hairpin assembly (mfCHA) is intriguing to regulate the fluorescence of DNA-scaffolded red Ag nanoclusters (rAgNC) for rapid and amplifiable biosensing of miRNA-155 (miR-155). Herein, we report the first design of a miR-155-responsive mfCHA route with rapid reaction kinetics and high conversion efficiency to light-up the fluorescence of rAgNC. The mfCHA was operated by a signaling hairpin (SH) programmed with the rAgNC template sequence and miR-155-discernible segment, and a G-rich (G12) enhancing hairpin (EH*). To implement faster and more efficient mfCHA amplification as a big challenge in traditional CHA, the locked stem of SH and the loop of EH* were encoded with single mismatched base in different sites, endowing mfCHA with more negative reaction standard free energy as driving force. Note that the originally synthesized rAgNC in SH was non-emissive. However, the presence of miR-155 initiated hairpin assembly between SH and EH* , leading to the displacement of miR-155 for repeated recycling and progressive mfCHA. Rationally, the red fluorescence of rAgNC was remarkably lighted-up due to the proximity to G12 enhancer in the shared dsDNA duplex products. Thus, this mfCHA-based assay platform displayed good simplicity, cost-effectiveness, rapidness, high sensitivity, and potential application for cell imaging.