Design mitochondria-specific fluorescent turn-on probes targeting G-quadruplexes for live cell imaging and mitophagy monitoring study

Parallel G-Quadruplex DNA Structures from Nuclear and Mitochondrial Genomes Trigger Emission Enhancement in a Nonfluorescent Nano-aggregated Fluorine–Boron-Based Dye

“…12,13,27,28,47,16 To validate the ability of 4b to target G4 DNA structures in HeLa cells, we performed a competition assay by using the G4-specific ligand BRACO-19, which has been previously used to identify selective molecular probes for nuclear and mitochondrial DNA G4s. 55 The 4b-associated emission in the extranuclear and nuclear regions decreased significantly in the presence of increasing concentrations of BRACO-19, confirming the specific binding of 4b to mitochondrial and nuclear DNA G4s (Figure 5D). To summarize, G4s are reported to play regulatory roles during mitochondrial transcription; however, unlike nuclear DNA G4s, still very little is known about other roles and functions of mtDNA G4s.…”

“…To test this hypothesis, we fixed and permeabilized HeLa cells before treating them with 4b . We detected the accumulation of 4b at both extranuclear and nuclear levels with clear peaks in the subnuclear compartments whose appearance was compatible with that of nucleoli. ,, Detection of nucleolar localization is typical for many fluorescent G4 ligands as nucleoli accommodate the multicopy G4-rich ribosomal genes. ,,,,, To validate the ability of 4b to target G4 DNA structures in HeLa cells, we performed a competition assay by using the G4-specific ligand BRACO-19, which has been previously used to identify selective molecular probes for nuclear and mitochondrial DNA G4s . The 4b -associated emission in the extranuclear and nuclear regions decreased significantly in the presence of increasing concentrations of BRACO-19, confirming the specific binding of 4b to mitochondrial and nuclear DNA G4s (Figure D).…”

Structurally diverse G-quadruplexes as the noncanonical nucleic acid drug target for live cell imaging and antibacterial study

“…We found that, apart from adopting a planar core molecular fragment to construct G4-ligands, the overall molecular size, 116 symmetry, 117,118 flexibility, 83 and the character of terminal groups 119–122 may affect the in vitro selectivity of the ligand toward G4-structures against RNA, single- and double-stranded DNA. Our study suggests that some small-sized molecular scaffolds including benzothiazole-benzofuroquinolinium, 123,124 benzothiazole-indolium, 125 1-methylquinolinium, 126 thiazole orange 81,84,127 and benzo[ e ]indole 128 are good molecular fragments for the design of fluorescent G4-ligands to achieve high discrimination ability, sensitivity and quantum yield targeting certain types of G4s for in vitro sensing and live cell imaging. In the design of G4-ligands, the molecular symmetry of G4-ligands has been rarely discussed in the literature.…”

“…We have recently developed a mitochondria-specific fluorescent ligand with the use of a planar molecular scaffold of benzo-indole to conjugate with a rotatable p -substituted styrene moiety via an ethylene bridge. 128 The ligand BYM was found to be selectively interacted with mtDNA G4s both in vitro and in cellulo and generated a red emission signal ( λ ex = 530 nm, λ em = 615 nm, Φ f = 0.389). The LOD of BYM targeting mtDNA G4 (mt6363) was determined to be 1.52 nM.…”

Advances in Small-Molecule Fluorescent pH Probes for Monitoring Mitophagy

“…Mitochondria are vital organelles in eukaryotic cells, serving as energy factories for cells and playing a crucial role in cellular energy supply, signal transduction, reactive oxygen species (ROS) production, calcium ion storage, cell differentiation, and cell death. − Mitochondria quantity and quality are maintained through the selective removal of damaged and excess mitochondria, a process known as mitophagy. This process involves the separation of damaged mitochondria into a double-membrane vesicle called an autophagosome, which subsequently binds to lysosomes, in which lysosomal enzymes break down the enclosed material into amino acids or small molecules that can be reused by the cell (Figure A). − Mitophagy alters the microenvironment of the mitochondria, including viscosity, polarity, and pH.…”