Fig. 4

Fluorescence signal amplification in DRET ternary systems targeting osk mRNA. Fluorescence emission spectra of the single-stranded D_P in the absence of target RNA, the ds-construct in absence of acceptor (D_P + osk) and the DRET-operating ternary systems: A. ([D_P + A4_P] + osk), B. ([D_P + A2_P] + osk), C. ([D_P + A0_P] + osk), and their corresponding acceptor cross-excitation. DRET between X and Cy5 led to 13-, 17-, and 20-fold increases in the fluorescence sensing signal. Observables were recorded at 2 μM, in pH 7.4 PBS and excitation was performed at 458 nm corresponding to the blue laser wavelength used in the further imaging experiments. Fluorescence signal amplification was determined according to the following equation: S/N = (F_hybrid—F_buffer)/(F_ss—F_buffer) (Eq. 3)⁶³.