Sensitive detection and imaging of endogenous peroxynitrite using a benzo[d]thiazole derived cyanine probe

A reversible and ratiometric fluorescent probe based on rhodol derivative with an ESIPT unit for monitoring copper ion content and in situ evaluation of related drugs in cells

The amount of copper ions in the environment has an immediate effect on ecology and food safety, Menkes syndrome and Wilson's disease cause accumulation and deficiency of copper ions in the body, respectively, and neurodegenerative diseases are also closely related to copper ion levels. However, the current copper ion detection technology has a high cost, complex operation, and other disadvantages. In this study, a ratiometric fluorescent probe (RB-DH) was rationally constructed to detect copper ions by coupling benzothiazole to rhodol derivatives. It can be used to determine copper ion concentrations in water samples, agricultural products, cells, and zebrafish. Importantly, due to the reversible response of RB-DH to copper ions, the fluctuation of intracellular copper ion content during the release of copper ion-related drugs (Copper gluconate and D-penicillamine) was successfully monitored with RB-DH for the first time. This study demonstrates RB-DH's potential application in the evaluation of related drug release effects and serves as a guide for the establishment of portable detection techniques for other important substances.

Recent Progress of Spectroscopic Probes for Peroxynitrite and Their Potential Medical Diagnostic Applications

Peroxynitrite (ONOO-) is a crucial reactive oxygen species that plays a vital role in cellular signal transduction and homeostatic regulation. Determining and visualizing peroxynitrite accurately in biological systems is important for understanding its roles in physiological and pathological activity. Among the various detection methods, fluorescent probe-based spectroscopic detection offers real-time and minimally invasive detection, high sensitivity and selectivity, and easy structural and property modification. This review categorizes fluorescent probes by their fluorophore structures, highlighting their chemical structures, recognition mechanisms, and response behaviors in detail. We hope that this review could help trigger novel ideas for potential medical diagnostic applications of peroxynitrite-related molecular diseases.

A mitochondrion targetable dimethylphosphorothionate-based far-red and colorimetric fluorescent probe with large Stokes shift for monitoring peroxynitrite in living cells

Peroxynitrite (ONOO^-) is a biological oxidant that is related to numerous physiological and pathological processes. An overdose of ONOO^- is the cause of various serious diseases. Some evidence demonstrates that mitochondria are the major sites of ONOO^- production. Therefore, monitoring mitochondrial ONOO^- is important to understand the related pathological processes in living systems. Herein, a colorimetric and far-red fluorescent sensing probe (PCPA) for the determination of ONOO^- was constructed based on a dicyanoisophorone skeleton using dimethylphosphorothionate as the recognition group and pyridine salt as the mitochondrion-targeting unit. PCPA showed a far-red fluorescence response to ONOO^- accompanied by a distinct color change from colorless to yellow via the ONOO^- induced deprotection of dimethylphosphorothionate. In addition, PCPA exhibited a large Stokes shift (200 nm), high selectivity detection and high sensibility (LOD = 39 nM). Furthermore, PCPA was successfully employed for imaging ONOO^- and tracing ONOO^- in mitochondria. PCPA presents a new recognition group and has potential applications in the biology field.

Methyl position affect the fluorescence performance of HBT derivatives for the detection of hypochlorite under alkaline condition

Five fluorescent derivatives of hydroxyphenyl-benzothiazole (HBT) with different methyl positions at the hydroxyphenyl group were synthesized with good yield. Their reactivity and fluorescent response to hypochlorite were carefully studied. It was found that the HBT derivatives with meta-methyl (3-HBT or 5-HBT) showed the highest reactivity to hypochlorite under basic conditions, accompanied by the most efficient fluorescence quenching, whereas HBT derivatives with ortho or para methyl exhibited the least reactivity to hypochlorite. The LUMO and HOMO of 3-HBT were further verified to explain the fluorescence behavior by density functional theory (DFT) calculation. The excellent selectivity of 3-HBT toward hypochlorite against other reactive oxygen species (ROS) was also evaluated under the same conditions. The compounds emit bright green fluorescence in a solid-state, which is convenient for designing sensing devices for hypochlorite in water samples. Thus, the HBT derivatives with meta methyl (3-HBT) were successfully applied to fabricate paper sensors for the quantification of hypochlorite in tap water. Hence, the fluorescent 3-HBT exhibits great promise as a selective and sensitive hypochlorite probe in chemical and biological applications.

A Fluorescent Probe Strategy for the Detection and Discrimination of Hydrogen Peroxide and Peroxynitrite in Cells

Aryl boronate fluorescent probes allow the non-invasive study of dynamic cellular processes involving the reactive species, hydrogen peroxide (H2O2) and peroxynitrite (ONOO-). However, the ability of these probes to differentiate...

A novel borate fluorescent probe for rapid selective intracellular peroxynitrite imaging

Peroxynitrite (ONOO^-) is one of the species of reactive nitrogen (RNS), which plays an important role in antibacterial activity and signal transduction and other physiological and pathological processes. In this paper, based on the benzyl borate group, a new fluorescent probe capable of detecting ONOO^- with high selectivity and sensitivity is designed, and the possible mechanism of the interaction between probe and ONOO^- is proposed. The probe shows high fluorescence response to ONOO^- in a wide pH range (7.0-11.5). Moreover, the probe exhibit good permeability, and the content of ONOO^- in cancer cells and normal cells was successfully monitored.

Non-covalent binding and selective fluorescent sensing of dipyrone with a carbocyanine dye and cetyltrimethylammonium bromide

The work is aimed at the search of selective fluorescent sensors without using specific artificial receptors, antibodies, enzymes etc. With this end in view, methods based on non-covalent binding of target analytes are sought. We observed dramatic changes in the emission spectrum of a carbocyanine dye in a micellar surfactant solution (cetyltrimethylammonium bromide, CTAB) in the presence of dipyrone (metamizol, analgin): the 480 nm band intensity increases with a simultaneous decrease in intensity in near-IR region (720 nm). MALDI and NMR-¹H data show the intact molecules of dipyrone and the dye. The detection can be performed in the presence of other organic species and inorganic salts. Dipyrone testing is feasible within 5 × 10^-7-5 × 10^-4M with RSDs of 3.5% by using a visualizer instead of a spectrofluorimeter.

Mechanisms of ebselen as a therapeutic and its pharmacology applications

Ebselen is a synthetic organoselenium radical scavenger compound that possesses glutathione peroxidase-like activity and its own unique bioactivity by reacting with thiols, hydroperoxides and peroxynitrites. Owing to its high affinity toward several essential reactions, ebselen protects cellular components from oxidative and free radical damage, and it has been employed as a useful tool for studying redox-related mechanisms. Based on numerous in vitro and in vivo research, mechanisms are proposed to understand the biomedical and molecular actions of ebselen in health and disease, and it is currently under clinical trials for the prevention and treatment of various human disorders. Based on these outstanding discoveries, this review summarizes the current understanding of the biochemical and molecular characteristics, pharmacological applications and future directions of ebselen.

A highly responsive, sensitive NIR fluorescent probe for imaging of superoxide anion in mitochondria of oral cancer cells

Superoxide anion (O₂^•-) is an important biomarker for reactive oxygen species (ROS) generated through physiological and pathological processes. However, due to the short half-life of O₂^•- and high autofluorescence of cell tissues, in situ real-time tracking and monitoring of endogenous O₂^•- can be difficult. In this paper, a fluorescent probe IFP-O₂ was developed to detect endogenous O₂^•- in cells. The probe could instantaneously react with O₂^•- to produce fluorescence off-on effect; its detection limit was as low as 10 nM. Cell experiments also showed that the probe had low toxicity and mitochondrial targeting ability. The article presents, for the first time, a probe that can be employed to measure endogenous O₂^•- in oral cancer Cal-27 cells and is a promising tool for monitoring and evaluating apoptosis.

A sensitive and selective fluorescent probe for the detection of endogenous peroxynitrite (ONOO-) in living cells

Peroxynitrite (ONOO-) is one of reactive oxygen species, and plays a vital role in numeorus physiological and pathological processes. Given that the ONOO- level is closely related with various serious diseases, the in situ and real time detection of endogenous ONOO- is highly important for the in-depth study of its roles in living systems. Herein, we present a new fluorescent probe (RHPN) for the real-time detection of intracellular ONOO-. The probe RHPN consists of a rhodamine analogue and an arylhydrazide group as a response site for ONOO-. In response to ONOO-, the probe RHPN converts to an open-ring form and generates strong fluorescence. Moreover, the probe RHPN was successfully used for the imaging of the endogenous and exogenous ONOO- level changes in living cells.

A highly selective and sensitive red-emitting fluorescent probe for visualization of endogenous peroxynitrite in living cells and zebrafish

Peroxynitrite (ONOO-) has been proven to participate in various physiological and pathological processes, and may also be a contributing factor in many diseases. In view of this, there is a need to develop detection tools for unambiguously tracking a small amount of endogenous ONOO- to reveal its exact mechanisms. In this paper, a colorimetric and red-emitting fluorescent probe Red-PN, based on a rhodamine-type fluorophore and hydrazide reactive site is described. The probe Red-PN possesses the advantages of rapid response (within 5 s), visual color change (from colorless to pink), preeminent sensitivity (detection limit = 4.3 nM) and selectivity. Because of these outstanding performances, it was possible to accurately detect endogenous ONOO-. It was encouraging that the probe Red-PN could be used effectively for tracking the relatively low levels of endogenous and exogenous ONOO- in living cells and zebrafish. Thus, it is envisioned that the probe Red-PN would have promising prospects in applications for imaging ONOO- in a variety of biological settings.

Novel Dimethylhydrazine-Derived Spirolactam Fluorescent Chemodosimeter for Tracing Basal Peroxynitrite in Live Cells and Zebrafish

The precise cellular function of peroxynitrite (ONOO^-) in biosystems remains elusive, primarily owing to being short of ultrasensitive techniques for monitoring its intracellular distribution. In this work, a novel rhodamine B cyclic 1,2-dimethylhydrazine fluorescent chemodosimeter RDMH-PN for highly specific and ultrasensitive monitoring of basal ONOO^- in biosystems was rationally designed. The fluorescence titration experiments demonstrated that RDMH-PN was capable of quantitatively detecting 0-100 nM ONOO^- (limit of detection = 0.68 nM). In addition, RDMH-PN has outstanding performances of ultrafast measurement, naked-eye detection, and preeminent selectivity toward ONOO^- to accurately detect intracellular basal ONOO^-. Finally, it has been confirmed that RDMH-PN could not only map the intracellular basal ONOO^- level by inhibition tests but also trace the fluctuations of endogenous and exogenous ONOO^- levels with diverse stimulations in live cells and zebrafish.