Disaggregation-driven far-red BODPIY dye for selective G4 DNA structures detection

Push-pull solvatochromic dyes undergoing intramolecular charge transfer (ICT) have emerged as useful tools for imaging target biomolecules directly in living cells and monitoring interactions of biomolecules by changing the signal of their fluorescence. However, the currently reported solvatochromic fluorescent dyes frequently suffer from the problem of inherit background noise, and cause unspecific fluorescence that masks the specific signal from biomolecules. Herein, based on the combined the effect of aggregation-caused quenching (ACQ), a D-π-A structural far-red BODIPY dye BSK was designed and developed as a G-quadruplex (G4) DNA structures probe. In organic solvents, the spectra results underlined the excellent characteristics of BSK, such as high polarity sensitivity and strong solvatochromic effect due to the electron donor–acceptor system. In aqueous solution, BSK underwent aggregation to form nonfluorescent amorphous aggregates in which the dye kept low background fluorescence in a solution. Upon binding of BSK with c-MYC G4 DNA, an intense fluorescence was trigged by the synergistic properties of disaggregation-induced emission and inhibited twisted intramolecular charge transfer, with a low detection limit of 16 nM. In addition, BSK exhibited a selective ability to target G4 DNA structures and effectively differentiated from duplex and single-strand DNAs. Moreover, BSK has the potential to be used in visualizing the cellular nucleus in cells.