A new xanthene-based fluorescent probe with a red light emission for selectively detecting glutathione and imaging in living cells

A near-infrared ratiometric fluorescent probe for hydrazine and its application for gaseous sensing and cell imaging

Hydrazine (N₂H₄) is a widely used raw material in the chemical industry, but at the same time hydrazine has extremely high toxicity. Therefore, the development of efficient detection methods is crucial for monitoring hydrazine in the environment and evaluating the biological toxicity of hydrazine. This study reports a near-infrared ratiometric fluorescent probe (DCPBCl₂-Hz) for the detection of hydrazine by coupling a chlorine-substituted D-π-A fluorophore (DCPBCl₂) to the recognition group acetyl. Due to the halogen effect of chlorine substitution, the fluorophore has an elevated fluorescence efficiency and a lowered pKa value and is suitable for physiological pH conditions. Hydrazine can specifically react with the acetyl group of the fluorescent probe to release the fluorophore DCPBCl₂, so the fluorescence emission of the probe system significantly shifted from 490 nm to 660 nm. The fluorescent probe has many advantages, such as good selectivity, high sensitivity, large Stokes shift, and wide applicable pH range. The probe-loaded silica plates can realize convenient sensing gaseous hydrazine with content down to 1 ppm (mg/m³). Subsequently, DCPBCl₂-Hz was successfully applied to detect hydrazine in soils. In addition, the probe can also penetrate living cells and allow the visualization of intracellular hydrazine. It can be anticipated that probe DCPBCl₂-Hz will be a useful tool for sensing hydrazine in biological and environmental applications.

A water-soluble fluorescent probe for monitoring mitochondrial GSH fluctuations during oxidative stress

In this research, we constructed a styrylpyridine derivative-based fluorescent probe MITO-PQDNs to monitor mitochondrial glutathione (GSH). The probe MITO-PQDNs could react rapidly (20 min) with GSH in PBS buffer and exhibited a strong fluorescence signal (586 nm) as well as a significant Stokes shift (200 nm). Moreover, MITO-PQDNs could quantitatively detect GSH with high sensitivity (LOD = 253 nM). Meanwhile, MITO-PQDNs possessed favorable biocompatibility and could detect both endogenous and exogenous GSH in MCF-7 cells. Above all, MITO-PQDNs enabled the detection of fluctuations in mitochondrial GSH concentrations during oxidative stress.

Oxidation of BINOLs by Hypervalent Iodine Reagents: Facile Synthesis of Xanthenes and Lactones

Xanthene derivatives have broad applications in medicines, fluorescent probes, dyes, food additives, etc. Therefore, much attention was focused on developing the synthetic methods to prepare these compounds. Binaphthyl‐based xanthene derivatives were prepared through the oxidation of BINOLs promoted by the hypervalent iodine reagent iodosylbenzene (PhIO). Nine‐membered lactones were obtained through a similar oxidative reaction when iodoxybenzene (PhIO₂) was used. Additionally, one‐pot reactions of BINOLs, PhIO and nucleophiles such as alcohols and amines were also investigated to provide alkoxylated products and amides in good to excellent yields.

Biocompatibility nanoprobe of MXene N-Ti3C2 quantum dot/Fe3+ for detection and fluorescence imaging of glutathione in living cells

MXene quantum dots have attracted much attention due to their great optical performance and excellent water solubility. Glutathione (GSH) plays a key role in living cells. In this study, a biocompatibility nanoprobe was prepared for detecting intracellular GSH based on MXene N-Ti₃C₂ quantum dots (N-Ti₃C₂ QDs). The N-Ti₃C₂ QDs act as the fluorescence reporters and the ferric iron (Fe³⁺) as the quenchers based on nonradiative electron-hole annihilation. When Fe³⁺ encounters the amino group of N-Ti₃C₂ QDs, the electrons of N-Ti₃C₂ QDs in the excited state will transfer to the half-filled 3d orbitals of Fe³⁺, leading to the fluorescence quenching of N-Ti₃C₂ QDs. When the N-Ti₃C₂ QDs/Fe³⁺ nanoprobe acts on the cancer cell MCF-7, the abundant GSH in the cancer cells can reduce Fe³⁺ to Fe²⁺, which will restore the fluorescence of N-Ti₃C₂ QDs. The N-Ti₃C₂ QDs/Fe³⁺ nanoprobe displays a high sensitivity for GSH with a detection limit of 0.17 μM in range of 0.5-100 μM. It becomes a promising probe for detecting and showing cellular imaging of GSH in MCF-7 cells. The N-Ti₃C₂ QDs/Fe³⁺ nanoprobe might provide a new way for imaging-guided precision cancer diagnosis.

A Pyrene-Based Fluorescent Probe for Specific Detection of Cysteine and its Application in Living Cell

Cysteine (Cys) is an essential amino acid in organism, which is transformed from methionine in vivo and participates in protein synthesis and cell redox process. Therefore, the detection of Cys is of great significance. In this work, a novel fluorescent probe, (E)-3-(2-chloroquinolin-3-yl)-1-(pyren-3-yl) prop-2-en-1-one (PAQ) was designed and synthesized to specifically detect Cys. The response mechanism of the reaction between PAQ and Cys was due to the addition reaction of Cys to α,β-unsaturated ketone of PAQ. Interestingly, the addition of Cys induced significant fluorescence intensity enhancement at 462 nm. PAQ exhibited favorable sensing properties towards Cys such as the low limit of detection (0.27 μM) and fast response speed (2 min). In addition, PAQ displayed high selectivity and anti-interference ability toward Cys among various analytes. Notably, PAQ has been successfully used to image exogenous and endogenous Cys in HeLa cells.

Recent Progress of Glutathione (GSH) Specific Fluorescent Probes: Molecular Design, Photophysical Property, Recognition Mechanism and Bioimaging

The selective detection of glutathione (GSH) in vitro and in vivo has attracted great attentions, credited to its important role in life activities and association with a series of diseases. Among all kinds of analytical techniques, the fluorescent probe for GSH detection become prevalent recently because of its ease of operation, high temporal-spatial resolution, visualization and noninvasiveness, etc. The special structural features of GSH, such as the nucleophilicity of sulfhydryl group, the concerted reaction ability of amino group, the negative charged nature, the latent hydrogen bonding ability along with its flexible molecular chain, are all potent factors to be employed to design the specific fluorescent probe for GSH and discriminate it from other bio-species including its analogues cysteine (Cys) and homocysteine (Hcy). This paper reviewed the studies in the last 3 years and was organized based on the reaction mechanism of each probe. According to the reactivity of GSH, various recognition mechanisms including Michael addition, nucleophilic aromatic substitution, ordinary nucleophilic substitution, multi-site reaction, and other unique reactions have been utilized to construct the GSH specific fluorescent probes, and the molecular design strategy, photophysical property, recognition mechanism, and bioimaging application of each reported probe were all discussed here systematically. Great progress has been made in this area, and we believe the analyses and summarization of these excellent studies would provide valuable message and inspiration to researchers to advance the research toward clinic applications.

Automated fluorimetric sensor for glutathione based on zone fluidics

A zone-fluidics (ZF) based automated fluorimetric sensor for the determination of glutathione (GSH) is reported. Discrete zones of GSH and o-phthalaldehyde (OPA) mix and react on-line under mild basic pH without the need of additional nucleophillic reagents, to yield a fluorescent isoindole derivative (λ_ex/λ_em = 340/425 nm). The proposed ZF sensor was optimized (pH, c(OPA), time, instrumental variables) and validated. Cysteine, glutamate, glycine and ammonium were representatively examined in terms of selectivity and were found not to react in 10-fold excess. Linearity was proved in the range of 5-100 μmol L^-1 GSH, with an LOD of 1 μmol L^-1 at a practical sampling rate of 20 h^-1 and RSD < 0.5% (within-day) and 4.2% (day-to-day). The dosage uniformity of commercially available GSH - containing nutraceuticals was evaluated.

Structure-Bioactivity Relationship Study of Xanthene Derivatives: A Brief Review

Over the last decades, several heterocyclic derivatives compounds have been synthesized or extracted from natural resources and have been tested for their pharmaceutical activities. Xanthene is one of these heterocyclic derivatives. These compounds consist of an oxygen-containing central heterocyclic structure with two more cyclic structures fused to the central cyclic compound. It has been shown that xanthane derivatives are bioactive compounds with diverse activities such as anti-bacterial, anti-fungal, anti-cancer, and anti-inflammatory as well as therapeutic effects on diabetes and Alzheimer. The anti-cancer activity of such compounds has been one of the main research fields in pharmaceutical chemistry. Due to this diverse biological activity, xanthene core derivatives are still an attractive research field for both academia and industry. This review addresses the current finding on the biological activities of xanthene derivatives and discussed in detail some aspects of their structure-activity relationship (SAR).