A commercially available NIR fluorescence probe for the detection of hypochlorite and its application in 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.

A Commercially Available 2-aminoanthracene Fluorescent Probe for Rapid and Sensitive Detection of Hypochlorite in 100% Buffer Solution and its Application in Complex Water Samples

Hypochlorite (ClO-), a crucial chemical in the living organism, engages in various physiological activities. However, high amounts of ClO- result in oxidative damage. In this work, a commercially available 2-aminoanthracene (AA) was used to detect ClO-. AA demonstrated distinct properties such as superior selectivity and rapid response (< 30 s) with a low detection limit (140 nM) towards ClO- in 100% buffer solution. Furthermore, the probe exhibited a notable achievement by effectively identifying the presence of ClO- in complicated water samples. In conclusion, AA offers an easy-to-use and accurate method for quantifying ClO- in complex water samples.

A pyridine modified naphthol hydrazone Schiff base chemosensor for Al3+ via intramolecular charge transfer process

A pyridine modified naphthol hydrazone Schiff base chemosensor, NaPy, was prepared in a two-step process to detect aluminum ion (Al3+) in different samples. The probe shows a turn-off emission response towards Al3+ at a 1:1 binding stoichiometry via intramolecular charge transfer (ICT) mechanism, as validated by density functional theory (DFT) calculations and a series of spectroscopic measurements. The response time is slightly over one minute with a limit of detection (LOD) value of 0.164 µM, demonstrating the great sensitivity of the probe. It is also found that NaPy exhibits high selectivity towards Al3+ and resists interference from seventeen other cations. Application investigations in paper strips, water samples and HeLa cells suggest that NaPy can be used as an efficient probe for sensing Al3+ in real environmental samples and biosystems.

A NIR fluorescent probe for the specific detection of hypochlorite and its application in vitro and in vivo

It is of great necessity to exploit a real-time, highly selective and sensitive method for hypochlorite (ClO^-) detection in both the environment and living systems because of the complex influence of ClO^- on health. In this paper, based on the intramolecular charge transfer (ICT) effect, a NIR fluorescent probe (probe DAB) was designed for the accurate detection of ClO^-, which produced a fluorescence response to ClO^- with high selectivity and rapid response (within 1 min). The probe DAB could determine ClO^- over the linear range of 0-80 μM with a low detection limit of 1.46 μM. And the sensing mechanism between the probe and ClO^- was verified using HPLC and MS. To further prove its practicability, the probe was applied for detecting ClO^- in actual water samples. In addition, owing to its good sensing properties and low cytotoxicity, probe DAB could be expediently applied to visualize ClO^- in living cells and zebrafish, and it is expected to be a useful tool for investigating the detailed functions and mechanisms of ClO^- in living systems.

Synthesis, optical properties, determination and imaging in living cells and bamboo of cinnamaldehyde derivatives

Two Schiff-base fluorescent probes (1 and 2) were directly synthesized from natural cinnamaldehyde, and they were characterized by FT-IR, ¹H and ¹³C NMR, HRMS. Compound 1 had no fluorescence, while compound 2 could emit significant yellow fluorescence in solid and provide green light in solution. Probe 1 could selectively sense ClO^- with a fluorescence enhancement, providing a good linear relationship between the fluoresence intensity and ClO^- concentrations (0-5.5 × 10^-5 mol/L), y = 175.64x-19.399, R² = 0.9937, and the limit of detection (LOD) was 39.4 nM. Probe 2 was sensitive for Cu²⁺ by quenching with two linear relationships at the Cu²⁺ concentrations from 0 to 2.1 × 10^-5 mol/L, LOD = 73.9 nM. Furthermore, live celluar imaging of human astrocytoma U-251 MG cells and human liver cancer cells (Hu-7) had achieved using the 1 + ClO^- and 2, offering clear intracellular fluorescence. Finally, the 1 + ClO^- and 2 could also be used to dye bamboo tissues for a good use. Thus, the cinnamaldehyde derivatives could be further used in the field of celluar and bamboo imaging.

Rational Design of Meso-Phosphino-Substituted BODIPY Probes for Imaging Hypochlorite in Living Cells and Mice

Meso-phosphino-substituted BODIPY probes were developed for concise and rapid detection of hypochlorite (ClO^-). Interestingly, the probe BP gave a turn-on fluorescence response by shutting the photoinduced electron transfer (PET) effect and extending the coplanar conjugated π-system. In contrast, the probe TMBP showed a colorimetric response toward ClO^-. The key role of the steric repulsions was revealed to be for altering the electronic distribution of the BODIPY core, resulting in these obviously different responses. Finally, the probe BP, with high selectivity and sensitivity toward ClO^- (LOD = 1.9 nM; response time, <15 s), was further employed in imaging the variations of exogenous and endogenous hypochlorite (ClO^-) in living RAW 264.7 cells and mouse inflammation models. If wisely utilized, this strategy with meso-phosphino BODIPY dyes may serve as a powerful platform for the preparation of novel chemosensors.