A ratiometric fluorescent probe for sensing hypochlorite in physiological saline, bovine serum albumin and fetal bovine/calf serum

Facile synthesis of long-wavelength emission carbon dots for hypochlorite sensing and intracellular pH imaging

Hypochlorite (ClO-), a typical reactive oxygen species, plays an irreplaceable roles in various biological processes. In this work, long-wavelength emission carbon dots (LW-CDs) were fabricated through one-step hydrothermal method by using l-cysteine (cys) and neutral red (NR) as precursors for monitoring of hypochlorite and intracellular pH. Characterizations of as-prepared LW-CDs showed that they had excellent water solubility, high optical stability and sensitive response behavior. Fluorescence intensity of LW-CDs decayed in the presence of ClO- linearly from 10 to 162.5 μM (LOD = 1.021 μM) based on static quenching effect with ideal selectivity. Besides, LW-CDs revealed a pH responsive behavior in the pH range of 2.0 to 10.0, exhibited dual good linear relationships in the pH ranges of 4.2-5.8 and 5.8-7.4. The LW-CDs can also be utilized as imaging reagents in Hela living cells owing excellent biocompatibility and low cytotoxicity. These results demonstrated that the as-mentioned LW-CDs are expected to serve as excellent long wavelength emitting nanomaterials for fluorescence sensing and monitoring of cell fluctuations.

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.

Detection and application of hypochlorous acid in both aqueous environments and living organisms

The scarcity of water resources has raised concerns regarding drinking water safety. Excessive addition of hypochlorous acid (OCl-) as a disinfectant in drinking water can result in severe consequences. Moreover, abnormal levels of OCl- within the human body can lead to various diseases. Employing fluorescence analysis, the design and synthesis of specific fluorescent probes for simultaneous detection of OCl- in water environments and living organisms holds strategic significance in ensuring the safety of drinking water and mitigating potential risks caused by its abnormal concentrations. This article utilizes naphthalimide as a precursor to develop a novel probe enabling highly sensitive detection of OCl- in water environments and at the organelle level within living organisms. This endeavor serves to provide assurance for drinking water safety and offers health alerts.

Development of a novel hypochlorite ratio probe based on coumarin and its application in living cells

Hypochlorous acid is a reactive oxygen species that is widely present in the body and has been found to exhibit an elevated concentration in tumors. As a result, fluorescent probes for tumor detection have recently gained significant attention. In this study, we designed and synthesized a novel ratiometric fluorescent probe, LW-1, using coumarin as a scaffold, and characterized its spectral properties. LW-1 displayed indigo blue fluorescence at low concentrations of hypochlorous acid. As the concentration of hypochlorous acid increased, the probe underwent a reaction, resulting in a red shift in its fluorescence peak and exhibiting green fluorescence. The fluorescence intensity ratio (green/blue) was a susceptible detection signal for HClO. LW-1 exhibited favorable characteristics, including a low detection limit, high sensitivity, good stability, and low background interference. The detection limit has reached 2.4642 nM. Moreover, we successfully employed LW-1 to image normal human liver and colon cancer cells in vitro, demonstrating its potential as a promising tool for tumor detection. Overall, our findings suggest that LW-1 could serve as a valuable addition to the current arsenal of fluorescent probes for tumor detection, with potential applications in the diagnosis and treatment of cancer.

ESIPT-based probes for cations, anions and neutral species: recent progress, multidisciplinary applications and future perspectives

Fluorescent and colourimetric probes for small analytes (cations, anions and neutral molecules) have drawn significant attention in recent years. These probes interact with analytes and induce spectral change due to the variations in the photo-physical properties of the fluorophore/chromophore used. Among several photo-physical mechanisms, ESIPT (excited state intramolecular proton transfer) based probes are more advantageous due to their photo-physical properties viz. solvent polarity effect, large spectral shift with multi-channel fluorescence, high quantum yield etc. In recent years, ESIPT-based probes have shown several promising applications, especially monitoring small analytes in biological samples, smartphone app-assisted heavy metal detection in environmental samples, inkless writing, anti-counterfeiting applications etc. Therefore, this review is dedicated to recently reported ESIPT-based probes for small analytes. We have highlighted the organic units responsible for the ESIPT mechanism, their photo-physical parameters, selectivity and sensitivity properties and recent advances in their applications.