Fig. 2. Fluorescence spectral response of the DTNSs (37.5 nM) to varied targets miRNA-21 (A), miRNA-122 (B) and miRNA-194 (C) at different concentrations in a homogeneous solution, respectively. Black (0 nM), red (0.15 nM), blue (0.3 nM), darkcyan (0.6 nM), magenta (1.2 nM), dark yellow (2.3 nM), navy (4.7 nM), wine (9.4 nM), pink (18.8 nM), olive (37.5 nM), and royal (75 nM). In each case, the quenched fluorescence was recovered upon addition of target miRNAs in a concentration-dependent manner (D–F). Error bars show the standard deviation of three experiments. (G) Simultaneous detection of multiple miRNAs in solution. A mixed solution consisting of different components of miRNA targets (75 nM) was treated with DTNSs (37.5 nM). The fluorescence responses under three excitation/emission wavelengths (488 nm/520 nm for miRNA-21, 552 nm/580 nm for miRNA-122, 643 nm/660 nm for miRNA-194) were collected. The fluorescence emission spectra of FAM, TAMRA or Cy5 were obtained only in response to miRNA-21, miRNA-122 or miRNA-194 targets and had no notable cross-reactivity with each other.