Programmed Dual-Functional DNA Tweezer for Simultaneous and Recognizable Fluorescence Detection of microRNA and Protein.

A programmed dual-functional DNA tweezer (DFDT) as a signaling molecule is reported for the simultaneous and recognizable fluorescence detection of microRNA 21 (miRNA 21) and mucin 1 (MUC1). This unique DFDT is assembled from two Au-NP-attached central strands (C1 and C2) and an arm strand (A) dually ended by fluorophores Cy3 and Cy5, which are spatially separated from Au NP in the originally opened state. Through the competitive affinity interaction between targets and their complementary and aptamer sequences tethered in two recognition strands (R1 and R2), miRNA 21 and MUC1 are respectively converted into two dependently displaced fuel strands (F1 and F2). The next hybridization with two pairs of unpaired segments overhung in open DFDT leads to its conformational closure, resulting in the approach of Cy3 and Cy5 to Au NP. On the basis of the nanometal surface energy transfer scheme, the fluorescence emission of Cy3 or Cy5 is cooperatively quenched by Au NPs attached in C1 and C2. The significant variation of fluorescence intensity enables one-step, cost-effective, and specific quantization of miRNA 21 and MUC1 with high sensitivity down to 32 fM and 2.6 fg·mL (8.5 pM), respectively. The novel DFDT-based assay route of multiplex analytes is promising and has the potential for rapid and reliable diagnosis and treatment of cancer-related diseases.