A carbazole-based fluorescent probe for ultra-fast detection of ClO− and its application to live cell imaging

Ex Tenebris Lux: Illuminating Reactive Oxygen and Nitrogen Species with Small Molecule Probes

Reactive oxygen and nitrogen species are small reactive molecules derived from elements in the air─oxygen and nitrogen. They are produced in biological systems to mediate fundamental aspects of cellular signaling but must be very tightly balanced to prevent indiscriminate damage to biological molecules. Small molecule probes can transmute the specific nature of each reactive oxygen and nitrogen species into an observable luminescent signal (or even an acoustic wave) to offer sensitive and selective imaging in living cells and whole animals. This review focuses specifically on small molecule probes for superoxide, hydrogen peroxide, hypochlorite, nitric oxide, and peroxynitrite that provide a luminescent or photoacoustic signal. Important background information on general photophysical phenomena, common probe designs, mechanisms, and imaging modalities will be provided, and then, probes for each analyte will be thoroughly evaluated. A discussion of the successes of the field will be presented, followed by recommendations for improvement and a future outlook of emerging trends. Our objectives are to provide an informative, useful, and thorough field guide to small molecule probes for reactive oxygen and nitrogen species as well as important context to compare the ecosystem of chemistries and molecular scaffolds that has manifested within the field.

Lipid droplets-specific fluorescent probe for wash-free imaging and in vivo diagnosis of non-alcoholic fatty liver disease

Lipid droplets (LDs) dysfunction is closely associated with a multitude of diseases, including nonalcoholic fatty liver disease (NAFLD). Therefore, it is imperative to develop fluorescent probes that specifically target LDs for the early detection and diagnosis of NAFLD. In this study, a series of lipophilic fluorophores CZ1-CZ4 that feature a D-π-A configuration were designed and synthesized based on the carbazole and tricocyanofuran derivatives. The photophysical data revealed that all four probes exhibited large Stokes shifts (~ 120 nm) in high-polarity solvents (e.g., DMSO) and demonstrated enhanced fluorescence in solvents ranging from low-polarity (e.g., 1,4-Dioxane) to high-polarity. Notably, by utilizing probe CZ1, we could specifically visualize LDs and captured high-quality images, even eliminating the need for a time-consuming wash procedure. Moreover, CZ1 enabled monitoring of LDs dynamic changes in-real time within live cells, and importantly, it could be used to effectively distinguish normal and NAFLD tissues at both the organ and in vivo level. This exceptional property of probe CZ1 provides a practical tool for the diagnosis and intervention of NAFLD.

A Carbazole-based Fluorescent Turn-off Chemosensor for Iron (II/III) Detection in a Dimethyl Sulfoxide

We designed a novel carbazole-based chemosensor from 2-(N-hexylcarbazol-3'-yl)-pyridine-5-carbaldehyde which was named probe 7b. The main purpose of this study is to investigate whether metal ions in liquid media can be detected with probe 7b. The details were presented in this paper. First, the molecular absorption and fluorescence properties of probe 7b were characterized by spectrophotometers. Then, several methods were applied to check its sensing properties. The results showed that probe 7b has a sense towards Fe3+ ion than other interfering metal ions. The selectivity and sensitivity of probe 7b towards Fe3+ were very satisfactory to use in applications. Also, it was observed that when aqueous Fe3+ ion solutions were added to probe 7b in dimethyl sulfoxide (DMSO), the fluorescence intensity of probe 7b decreased. This situation (turn-off of emission) is due to the paramagnetic effect between probe 7b and Fe3+ ions. The limit of detection (LOD) value was found as 1.38 nM for probe 7b. This value is very small to compete with its counterparts in the literature. A real sample experiment indicated that probe 7b can detect Fe3+ ions more than other ions in real media, too. As a result, it was deduced that probe 7b is a very strong candidate to use in sensor technology.

A dicyanoisophorone-based fluorescent probe for hypochlorite with a fast response and its applications in bioimaging

One kind of phenolic substituted dicyanoisophorone derivative (Is-OL) has been designed and successfully synthesized for the detection of hypochlorite in water samples, test strips and living HeLa cells. The probe Is-OL showed high sensitivity and selectivity to hypochlorite over other competitive ROS and metal ions. Moreover, Is-OL can react instantaneously with hypochlorite (<5 s) while exhibiting a significant color change from yellow to colorless, which makes "naked-eye" detection possible with a low detection limit (0.095 μM). The results based on water tests and living HeLa cell experiments showed that Is-OL could be applied as a potential candidate for the detection of hypochlorite.

A novel ratiometric fluorescent probe based on thienocoumarin and its application for the selective detection of hypochlorite in real water samples and in vivo

A novel ratiometric fluorescent probe based on thieno[3,2-c]coumarin has been prepared for sensing hypochlorite, which could exhibit a large emission shift and a 338-fold emission ratio (I₄₇₀/I₆₄₀).