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

Exploring base mismatching-fueled catalytic hairpin assembly (mf CHA) is intriguing to regulate the fluorescence of DNA-scaffolded red Ag nanoclusters (r AgNC) for rapid and amplifiable biosensing of miRNA-155 (miR-155). Herein, we report the first design of a miR-155-responsive mf CHA route with rapid reaction kinetics and high conversion efficiency to light-up the fluorescence of r AgNC. The mf CHA was operated by a signaling hairpin (SH) programmed with the r AgNC template sequence and miR-155-discernible segment, and a G-rich (G12) enhancing hairpin (EH*). To implement faster and more efficient mf CHA 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 mf CHA with more negative reaction standard free energy as driving force. Note that the originally synthesized r AgNC 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 mf CHA. Rationally, the red fluorescence of r AgNC was remarkably lighted-up due to the proximity to G12 enhancer in the shared dsDNA duplex products. Thus, this mf CHA-based assay platform displayed good simplicity, cost-effectiveness, rapidness, high sensitivity, and potential application for cell imaging. [Display omitted] • A sensitive fluorescence biosensor is developed by using red AgNC (r AgNC) as signaling reporter. • Base mismatching of reactive hairpin stem is designed to fuel catalytic hairpin assembly (mf CHA). • The mf CHA route owns faster reaction kinetics and higher conversion efficacy than traditional CHA. • The r AgNC fluorescence emission is remarkably lighted-up when placing close to a G12 enhancer. • The targeting input is repeatedly displaced and recycled for amplifiable assay and cell imaging. [ABSTRACT FROM AUTHOR]