A highly selective naked-eye probe for hypochlorite with the p-methoxyphenol-substituted aniline compound

Activatable fluorescent probes for atherosclerosis theranostics

The onset of atherosclerosis (AS) is insidious, and early stage patients have atypical clinical symptoms. After being diagnosed in late stage, it is often prone to sudden and fatal cardiovascular events. Therefore, it is highly desirable to develop precise and efficient diagnosis and therapy strategies of AS. Benefiting from high signal-to-noise ratio, low detection limit, high specificity and sensitivity, a series of activatable fluorescent probes based on atherosclerotic microenvironment have emerged for identification and treatment of AS. In this review, we focus on the atherosclerotic microenvironment and briefly summarize the correlation between the structural transformation and fluorescence signal changes of mono-/double-activatable fluorescent probes upon biomarkers stimulation. Moreover, their cutting-edge progress for AS theranostics is described. Finally, the outlook for activatable theranostic probes based on atherosclerotic microenvironment is discussed to aim at promoting innovative research in imaging-guided precise AS therapy.

Assessing Early Atherosclerosis by Detecting and Imaging of Hypochlorous Acid and Phosphorylation Using Fluorescence Nanoprobe

The assessment of early atherosclerosis (AS) is of great significance for the early diagnosis and mechanism research. Herein, a novel nanoprobe PCN@FL is developed to realize the simultaneous detection and imaging of phosphorylation and hypochlorous acid (HClO). The selective recognition of HClO is achieved through the specific interaction between DMTC and HClO, while the levels of phosphorylation are detected via the specific interaction between Zr (IV) and phosphates. The nanoprobe can be utilized to monitor the fluctuations in HClO and phosphate in early atherosclerosis. It is observed that the levels of HClO and phosphate in the serum of early AS mice are higher than those of the normal mice. Ultimately, the levels of hypochlorous acid and phosphorylation in the inner wall of aortic vessels are imaged by two-photon microscope. The results show that the levels of HClO and phosphorylation in the early atherosclerotic mice are significantly higher than those of in normal mice. The nanoprobe provides a suitable fluorescent tool for simultaneous detection and imaging of HClO and phosphorylation, which holds promise for early atherosclerotic disease assessment.

Selective Ligand-Doped Liquid Crystal-Based Sensing Platform for Detection of ClO- Ions in Aqueous Media

The liquid crystal (LC) detection platform has been fabricated for the detection of hypochlorite ions (ClO^-) in aquatic solutions. In this system, an imine consisting of the ligand (E)-2-((4-(diethylamino)-2-hydroxybenzylidene)amino)-5-methoxybenzenesulfonic acid (MBA) was doped in 4-cyano-4'-pentyl biphenyl as a selecting LC for ClO^-. When immersing the platform in a solution containing ClO^-, hypochlorite appears to react with the imine bond in the MBA, and cause it to cleave, which eventually disrupts the direction of LC and causes a dark-to-bright conversion of the LC image. The detection limit for ClO^- is 0.05 μM. This sensory platform was unresponsive to NO₃ ^-, BrO₃ ^-, CH₃COO^-, CO₃ ^2-, and PO₄ ^3- ions. Our sensing platform also detected ClO^- in piped water. Since this sensory platform is colored under ambient light, it is easy for regular operators, and it can be used as a mobile tool for monitoring water quality anywhere.

New Application of the Commercially Available Dye Celestine Blue B as a Sensitive and Selective Fluorescent “Turn-On” Probefor Endogenous Detection of HOCl and Reactive Halogenated Species

Hypochlorous acid (HOCl) derived from hydrogen peroxide and chloride anion by myeloperoxidase (MPO) plays a significant role in physiological and pathological processes. Herein we report a phenoxazine-based fluorescent probe Celestine Blue B (CB) that is applicable for HOCl detection in living cells and for assaying the chlorinating activity of MPO. A remarkable selectivity and sensitivity (limit of detection is 32 nM), along with a rapid “turn-on” response of CB to HOCl was demonstrated. Furthermore, the probe was able to detect endogenous HOCl and reactive halogenated species by fluorescence spectroscopy, confocal microscopy, and flow cytometry techniques. Hence, CB is a promising tool for investigating the role of HOCl in health and disease and for screening the drugs capable of regulating MPO activity.

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.

Connecting the Dynamics and Reactivity of Arylboronic Acids to Emergent and Stimuli-Responsive Material Properties

Over the past two decades, arylboronic acid-functionalized biomaterials have been used in a variety of sensing and stimuli-responsive scaffolds. Their diverse applications result from the diverse reactivity of arylboronic acids,...

The reduction performance of double bonds regulated by the competition of push-pull electron groups to realize the colorimetric and fluorescence recognition of hypochlorous acid

Based on its reducibility, the double bond can act as a reaction site for hypochlorous acid (HOCl), which had been demonstrated by a great deal of work. Nevertheless, the reactivity is influenced by the adjacent chemical environment. Therefore, in this work, we constructed a probe (QI) by methoxy-substituted quinoline conjugating dicyanoisoflurone, in which dicyano and pyridine N act as electron-withdrawing groups and the methoxy acts as an electron-donating group, to regulate their adjacent C[double bond, length as m-dash]C reactivity. The "push-pull" electron effect between the methoxy group and the pyridine N led to the C[double bond, length as m-dash]C bond being passivated. On the other hand, another C[double bond, length as m-dash]C bond was activated by the strong electron-pulling effect of the dicyano group. Thus, the previously weak intramolecular charge transfer became stronger after the dicyano adjacent to the C[double bond, length as m-dash]C was oxidized by HOCl, and showed a strong emission shifted from 570 to 520 nm along with a color change. The reaction mechanism was verified by mass spectrometry, NMR and theoretical calculation, and further bioimaging demonstrated the practical application of the probe.

A new red fluorescent probe based on rosamine–phenothiazine for the highly selective and rapid detection of hypochlorite and its bioimaging in live cells

A new red fluorescent probe based on rosamine–phenothiazine for highly selective and rapid detection of hypochlorite and its bioimaging in live cells.

Self-assembled nanofibers of perylene diimide for the detection of hypochlorite in water, bio-fluids and solid-state: exogenous and endogenous bioimaging of hypochlorite in cells

PDI–DAMN shows the disintegration of nanofibers into flake-like aggregates with ‘turn-on’ fluorescence response on the addition of ClO⁻ in solid-state, bio-fluids and MG-63 cells.

A Redox-Switchable Colorimetric Probe for "Naked-Eye" Detection of Hypochlorous Acid and Glutathione

We report the development of a new colorimetric probe (L-ol) for investigations of the redox process regulated by hypochlorous acid (HOCl) and glutathione (GSH). The HOCl/GSH redox-switching cycle process was investigated in detail by UV-vis absorption spectroscopy, colorimetric analysis assay and high-resolution mass spectrometry (HRMS). The switchable absorbance responses were attributed to the HOCl-induced oxidation of the p-methoxyphenol unit to the benzoquinone derivative (L-one) and sequential reduction of L-one to hydroquinone (L-ol') by GSH. In phosphate-buffered saline (PBS) buffer, the absorbance of L-ol at 619 nm underwent a remarkable bathochromic-shift, accompanied by a color change from pale yellow to blue in the presence of HOCl. With further addition of GSH, the absorbance of L-one exclusively recovered to the original level. Meanwhile, the blue-colored solution returned to the naive pale yellow color in the presence of GSH. The detection limits for HOCl and GSH were calculated to be 6.3 and 96 nM according to the IUPAC criteria. Furthermore, L-ol-loaded chromatography plates have been prepared and successfully applied to visualize and quantitatively analyze HOCl in several natural waters.

A mitochondria-targeted near-infrared fluorescent probe with a large Stokes shift for real-time detection of hypochlorous acid

A real-time mitochondria-targeted near-infrared fluorescent probeLhas been synthesized with large Stokes shifts, and high selectivity and sensitivity.

A reversible and turn-on type fluorescence behaviour of hydrogen sulfide via a redox cycle between selenoxide and selenide

Upon treatment with H₂S in MeCN–PBS, the fluorescence dormant selenoxides of dibenzobarrelene- and benzobarrelene-based 1-seleno-1,3-butadiene derivatives are rapidly converted to strongly fluorescent selenides.

A novel pyridyl triphenylamine-BODIPY aldoxime: Naked-eye visible and fluorometric chemodosimeter for hypochlorite

An aldoxime containing fluorescent probe based on vinylpydine-appended triphenylamine-BODIPY has been designed and used for hypochlorite detection. OX-PPA-BODIPY was developed by introducing an aldoxime group into the 2-position of BODIPY, which can be used for the detection of hypochlorite with a sharp color change from pink to green. The attachment of 4-vinylpyridine moiety to triphenylamine-BODIPY constructs a fluorogen with desirable conjugated system. The probe, which displays extremely weak fluorescence owing to the CN isomerization mechanism at 2-position of BODIPY, responds to HClO/ClO^- through a dramatic enhancement of its fluorescence intensity. This new probe, a naked-eye visible and fluorometric chemodosimeter, exhibits high selectivity and sensitivity toward hypochlorite over other reactive oxygen species (ROS) and anions. The detection is accompanied by a 20-fold increase in fluorescent intensity (Φ_F from 0.02 to 0.43). The detection limit of the probe for hypochlorite is 7.37×10^-7M. Moreover, OX-PPA-BODIPY can be used to detect hypochlorite in real water samples.

Phenolic sensor development based on chromium oxide-decorated carbon nanotubes for environmental safety

A nanocomposite (NC) composed of chromium(III)oxide nanomaterials decorated carbon nanotubes (Cr₂O₃-CNT NC) was prepared via a simple solution method with reducing agents in an alkaline medium. The Cr₂O₃-CNT NC was characterized using ultraviolet-visible (UV/Vs.) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, energy-dispersive X-ray spectroscopy (XEDS), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and field-emission scanning electron microscopy (FESEM). The Cr₂O₃-CNT composite was deposited on a flat glassy carbon electrode (GCE) with conducting nafion (5%) binders to produce a sensor that exhibited fast response and high selectivity toward 4-methoxyphenol (4MP) in phosphate buffer phase at pH 7. Furthermore, the sensor performance parameters, including the sensitivity, lower detection range, reliability, and reproducibility, ease of integration, long-term stability, and selectivity were investigated in detail. The calibration plot was found to be linear in the concentration range of 0.01 nM-0.1 μM. The sensitivity and detection limit were calculated as 1.4768 μA cm^-2 μM^-1 and 0.06428 ± 0.0002 nM (at a signal-to-noise ratio of 3), respectively. Thus, it was concluded that the proposed selective and efficient sensor represents a promising approach to effectively detect toxic phenolic compounds in the environment with acceptable and reliable results.

Visual and optical detection of hypochlorite in water samples based on etching of gold/silver alloy nanoparticles

In this work, we have described the cost-effective, simple, selective and sensitive approach for the detection of hypochlorite (ClO⁻) using gold/silver alloy nanoparticles (Au/Ag alloy NPs) as a colorimetric probe.

The detection for hypochlorite by UV-Vis and fluorescent spectra based on oxidized ring opening and successive hydrolysis reaction

In this work, two high selective and sensitive fluorescent probes for ClO(-), 7-Hydroxycoumarin and 4-Hydroxycoumarin were designed. The reaction mechanism that we speculated was the oxidized ring opening reaction and hydrolysis. The detection could be realized in quasi-aqueous phase and the detection limits of probe [7] and probe [4] for ClO(-) were found to be 56.8nM and 70.5nM. Furthermore, the probes can be used to cell imagings.

Recent progress in chromogenic and fluorogenic chemosensors for hypochlorous acid

Due to the biological and industrial importance of hypochlorous acid, the development of optical probes for HOCl has been an active research area. Hypochlorous acid and hypochlorite can oxidize electron-rich analytes with accompanying changes in molecular sensor spectroscopic profiles. Probes for such processes may monitor HOCl levels in the environment or in an organism and via bio-labeling or bioimaging techniques. This review summarizes recent developments in the area of chromogenic and fluorogenic chemosensors for HOCl.

Determination of hypochlorite by quenching the fluorescence of 1-pyrenylboronic acid in tap water

In neutral conditions, a new probe based on the oxidative conversion of 1-pyrenylboronic acid to 1-hydroxypyrene was established for the fluorescence signaling of practical hypochlorite.

Recent developments in curcumin and curcumin based polymeric materials for biomedical applications: A review

Turmeric (Curcuma longa) is a popular Indian spice that has been used for centuries in herbal medicines for the treatment of a variety of ailments such as rheumatism, diabetic ulcers, anorexia, cough and sinusitis. Curcumin (diferuloylmethane) is the main curcuminoid present in turmeric and responsible for its yellow color. Curcumin has been shown to possess significant anti-inflammatory, anti-oxidant, anti-carcinogenic, anti-mutagenic, anticoagulant and anti-infective effects. This review summarizes and discusses recently published papers on the key biomedical applications of curcumin based materials. The highlighted studies in the review provide evidence of the ability of curcumin to show the significant vitro antioxidant, diabetic complication, antimicrobial, neuroprotective, anti-cancer activities and detection of hypochlorous acid, wound healing, treatment of major depression, healing of paracentesis, and treatment of carcinoma and optical detection of pyrrole properties. Hydrophobic nature of this polyphenolic compound along with its rapid metabolism, physicochemical and biological instability contribute to its poor bioavailability. To redress these problems several approaches have been proposed like encapsulation of curcumin in liposomes and polymeric micelles, inclusion complex formation with cyclodextrin, formation of polymer-curcumin conjugates, etc.

A BODIPY aldoxime-based chemodosimeter for highly selective and rapid detection of hypochlorous acid

A BODIPY-based fluorescent probe integrated with an aldoxime unit shows a remarkable fluorescence ''turn-on'' response to hypochlorous acid (HOCl). The oxidative dehydrogenation of BODIPY aldoxime by HOCl results in a distinct fluorescence enhancement as well as a change in color from red to orange.

A selective colorimetric and fluorescent probe for the detection of ClO− and its application in bioimaging

Disperse Violet 26 is a commercially available fluorochrome used as an on–off fluorescent probe for the detection of ClO⁻, which is one of the biologically important reactive oxygen species (ROS), in HEPES : CH₃CN = 1 : 1 (v/v pH = 7.0) with an excellent selectivity and sensitivity for ClO⁻ compared to other analytes.

Chromogenic and fluorogenic chemosensors and reagents for anions. A comprehensive review of the years 2010-2011

This review focuses on examples reported in the years 2010-2011 dealing with the design of chromogenic and fluorogenic chemosensors or reagents for anions.

Hypochlorous acid turn-on fluorescent probe based on oxidation of diphenyl selenide

A BODIPY-based fluorescent probe, HCSe, has been successfully developed for the rapid detection of hypochlorous acid based on the specific HOCl-promoted oxidation of diphenyl selenide in response to the amount of HOCl. Confocal fluorescence microscopy imaging using RAW264.7 cells showed that the new probe HCSe could be used as an effective fluorescent probe for detecting HOCl in living cells.

Naked-eye visible and fluorometric dual-signaling chemodosimeter for hypochlorous acid based on water-soluble p-methoxyphenol derivative

The oxidation of a simple p-methoxyphenol derivative by HClO induces an intramolecular charge transfer from the end phenyl units to the middle benzoquinone, which leads to colorimetric and fluorescent changes. This detection can be run in aqueous solution with high selectivity over other reactive oxygen species.