DNA‐Templated Gold Nanoclusters for miRNA Diagnostics with Branched Hybridization Chain Reaction

In this study, a novel nonlinear branched hybridization chain reaction (BHCR) strategy is developed for accurate biosensing and bioimaging. Four fuel strands are designed. The first two assist the growth of primary long double‐stranded chain. Meanwhile, branched tails are left, which consist the trigger of downstream HCR with the second group of fuel strands. Branched DNA nanostructures are thus formed, which significantly amplify the information of initial target miRNA. Besides, the output fluorescent signal is originated from DNA‐templated gold nanoclusters (AuNCs). Surface ligands of AuNCs always play important roles in the regulation of optical mechanisms. Herein, peptide/DNA‐stabilized AuNCs are prepared. Phosphorothioate‐modified DNA (psDNA) is used as the template for in situ synthesis. The short peptide (Tyr‐Cys‐Tyr, YCY) is introduced as the protecting ligand, which benefits significant Stokes shift via a two‐step Förster resonance energy transfer. Coupling BHCR and AuNCs, this method performs satisfactory for in vitro fluorescent biosensing and intracellular bioimaging. It exhibits potential application for the investigation of miRNA‐related bioprocesses.