Embedded Files
In vitro and in cells detection of G4 formation, by light-up fluorescent sensing is a hot issue. In fact, it is a fast and sensitive detection method. Naphthalene diimides (NDIs) can be used for this goal, taking advantage of their G4 affinity and tuneable optical properties. Since the NDI core is intrinsically fluorescent, simple chemical modifications are used to suppress their emission and to have it restored upon G4 binding. Herein, we focused on the emission quenching driven by aggregation.
NDI-Groove Binders
NDI-Groove Binders
Fluorescent sensing of G-quadruplex nucleic acids (G4s) is an effective strategy to elucidate their role in vitro and in vivo. Small molecule ligands have often been exploited, producing an emission light up upon binding. Naphthalene diimides (NDIs), although potent G4 binders exhibiting red-NIR fluorophores, have only been marginally exploited, as they are usually quenched upon binding. cex-NDIs aggregate under aqueous solvents and as a result, their fluorescence is mostly quenched under physiological conditions. Upon G4 binding, they disaggregate into binding monomers, producing a fluorescent light-up with anti-parallel and hybrid G4s. Contrary, with parallel G4s a light-off was recorded.
SQUARAINE Dyes
SQUARAINE Dyes
Here, a new amphiphilic dicyanovinyl-substituted squaraine, SQgl, is reported to act as an NIR fluorescent light-up probe discriminating an extensive panel of parallel G4s while it is non-fluorescent in the aggregated state. The squaraine can form an unconventional sandwich p-complex binding two quadruplexes, which leads to a strongly fluorescent (QY=0.61) supramolecular architecture. SQgl is highly selective against non-quadruplex and non-parallel G4 sequences without altering their topology, as desired for applications in selective in vivo high-resolution imaging and theranostics
NDI-Dyads
NDI-Dyads
A non-fluorescent naphthalene diimide (NDI) dimer, conjugating red and blue NDI dyes, becomes red/NIR emitting upon G-quadruplex binding. The fluorescence of the G-quadruplex/dimer and the weakly emitting ds-DNA/dimer is the key feature for the development of new rationally engineered G-quadruplex sensors.
NDI-Coumarine Conjugates
NDI-Coumarine Conjugates
Red fluorescence light up probes for G-quadruplex nucleic acids made by coumarin-naphthalene diimide dyads exhibit selectivity and sensitivity affected by the nature and length of the tethering spacers. Medium length alkyl spacers (≤7 C atoms) proved to be optimal when exciting the emitting naphthalene diimide by energy transfer from the coumarin chromophore, while longer spacers enhance the sensing efficiency by direct excitation of the naphthalene diimide. Moreover, hydrophilic tertiary amines improve the probe efficiency compared to their quarternary ammonium salt analogues and polyethylglycol spacers almost completely erase it.
Report abuse