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.

Colorimetric and electrochemical detection of SARS-CoV-2 spike antigen with a gold nanoparticle-based biosensor

Since emerging in China in December 2019, COVID-19 has spread globally, wreaked havoc for public health and economies worldwide and, given the high infectivity and unexpectedly rapid spread of the virus responsible-that is, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-urged the World Health Organization to declare it a pandemic. In response, reducing the virus's adverse effects requires developing methods of early diagnosis that are reliable, are inexpensive and offer rapid response. As demonstrated in this article, the colorimetric and electrochemical detection of SARS-CoV-2 spike antigen with gold nanoparticle-based biosensors may be one such method. In the presence of the SARS-CoV-2 spike antigen, gold nanoparticles aggregated rapidly and irreversibly due to antibody-antigen interaction and consequently changed in colour from red to purple, as easily observable with the naked eye or UV-Vis spectrometry by way of spectral redshifting with a detection limit of 48 ng/mL. Moreover, electrochemical detection was achieved by dropping developed probe solution onto the commercially available and disposable screen-printed gold electrode without requiring any electrode preparation and modification. The method identified 1 pg/mL of the SARS-CoV-2 spike antigen and showed a linear response to the SARS-CoV-2 spike antigen ranging from 1 pg/mL to 10 ng/mL. Both methods were highly specific to detecting the SARS-CoV-2 spike antigen but not other antigens, including influenza A (i.e. H1N1), MERS-CoV and Streptococcus pneumoniae, even at high concentrations.

Electrophilic Cyanate As a Recognition Motif for Reactive Sulfur Species: Selective Fluorescence Detection of H2S

An ESIPT-based fluorescent dye, 3-hydroxyflavone, is chemically masked with an electrophilic cyanate motif in order to construct a fluorescent probe for cellular sulfur species. This novel probe structure, displays an extremely fast, highly sensitive and selective "turn-on" type fluorescent response toward H2S. We have also documented its utility for imaging of H2S in the living cells.

A BODIPY-based fluorescent probe for ratiometric detection of gold ions: utilization of Z-enynol as the reactive unit

Using an irreversible intramolecular cyclisation pathway triggered by gold ions, a boron-dipyrromethene (BODIPY) based fluorescent probe integrated with a reactive Z-enynol motif responds selectively to gold ions.

A unique triple-channel fluorescent probe for discriminative detection of cyanide, hydrazine, and hypochlorite

Herein, the first triple-channel fluorescent probe, TTB, excited at the same wavelength (λ_ex = 360 nm) in the same sensing medium for the detection and discrimination of cyanide, hydrazine, and hypochlorite, is disclosed. While a fluorescent white color appeared (λ_em = 470 nm) with the addition of cyanide ion into the probe solution, upon addition of hydrazine and hypochlorite, green (λ_em = 503 nm) and orange (λ_em = 585 nm) fluorescent colors, respectively, were observed. A naked-eye detection for the three ions was documented. With the appearance of orange color, a mega Stokes shift of 175 nm was observed. The probe exhibited excellent selectivity and lower detection limits of 0.24 μM, 4.1 nM and 0.27 μM, and dynamic ranges of 0.0-2.0 μM, 0.0-0.05 μM and 0.0-2.0 μM for cyanide, hydrazine and hypochlorite, respectively. The sensing mechanism was investigated through computational studies before and after the addition of cyanide, hypochlorite, and hydrazine, applying density functional theory (DFT), along with the calculation of optical properties by time-dependent DFT (TD-DFT) method. The results were found to be in good agreement with the experimental values. Remarkably, the probe, TTB, successfully detected cyanide, hydrazine, and hypochlorite in complex water samples. Moreover, the detection of cyanide was successfully performed in apricot kernels, as well as hypochlorite in fruits and vegetables.

A BODIPY/pyridine conjugate for reversible fluorescence detection of gold(iii) ions

A rare example of a fluorescent probe for the reversible detection of gold ions.

Fluorescein propiolate: a propiolate-decorated fluorescent probe with remarkable selectivity towards cysteine

A fluorescent probe decorated with an alkynyl ester unit (e.g. propiolate) displayed a selective turn-on type fluorescent response towards cysteine.

Triazatruxene-Rhodamine-Based Ratiometric Fluorescent Chemosensor for the Sensitive, Rapid Detection of Trivalent Metal Ions: Aluminium (III), Iron (III) and Chromium (III)

We investigated the ability of a novel triazatruxene-rhodamine-based (TAT-ROD) chemosensor to detect the trivalent metal ions aluminium (Al³⁺), iron (Fe³⁺) and chromium (Cr³⁺). Operating via the through-bond energy transfer (TBET) pathway, the chemosensor exhibited low detection limits of 23.0, 25.0 and 170.0 nM for Al³⁺, Fe³⁺ and Cr³⁺, respectively, along with high sensitivity and selectivity during a brief period (<15 s). The binding ratio of the chemosensor and trivalent metal ions achieved by Job's method was 3:1, and when we added ethylenediaminetetraacetic acid (EDTA), the sensing process reversed. Altogether, our TAT-ROD chemosensor marks the first triazatruxene-based colorimetric and fluorometric metal ion sensor reported in the literature.

A novel voltammetric method for the sensitive and selective determination of carbonate or bicarbonate ions by an azomethine-H probe

Our study involved a simple, sensitive voltammetric method of determining either carbonate or bicarbonate ions independently with azomethine-H and a disposable pencil graphite electrode. The reduction of azomethine-H-carbonate complexes at approximately -930 mV formed in acetic acid-acetate buffer solution (pH: 4.25) was evaluated as a response. Among the results, the limits of detection and analytical ranges for carbonate ions were 3.7 μg L^-1 and 9.9-700.0 μg L^-1 and for bicarbonate ions were 9.0 μg L^-1 and 35.0-700.0 μg L^-1, and the relative standard deviations for carbonate and bicarbonate ions ranged from 1.33% and 6.93% at different concentrations. After the proposed method was applied to water, sparkling water, seawater and baking powder samples, the results were statistically evaluated and compared with those obtained from the potentiometric auto-titration system. Last, the complex stoichiometry of both carbonate and bicarbonate ions was comprehensively investigated with fluorescence and ¹H-NMR spectroscopy.

Signal-Enhanced Electrochemical Determination of Quercetin with Poly(chromotrope fb)-Modified Pencil Graphite Electrode in Vegetables and Fruits

A novel signal-enhanced electrochemical sensing strategy was constructed for quercetin determination with a peculiarly developed poly(chromotrope fb)-modified activated pencil graphite electrode in vegetables and fruits. The oxidation signal of quercetin at 118 mV in an alcoholic solution served as the analytical response. The produced platform, characterized by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy, could detect 1.9 nM of quercetin in the range of 0.01-1.2 μM. The extracted quercetin contents of red onion, red cabbage, cranberry, black mulberry, black raisin, and carob were determined by both the developed method and UV-visible spectroscopy. The results were statistically evaluated at the 95% confidence level, and no significant difference between the results was found.

A novel thienothiophene-based "dual-responsive" probe for rapid, selective and sensitive detection of hypochlorite

BACKGROUND

Hypochlorite/hypochlorous acid (ClO-/HOCl) is a biologically crucial reactive oxygen species (ROS), produced in living organisms and has a critical role as an antimicrobial agent in the natural defense system. However, when ClO- is produced excessively, it can lead to the oxidative damage of biomolecules, resulting in organ damage and various diseases. Therefore, it is imperative to have a straightforward, quick and reliable method for over watching the minimum amount of ClO- in different environments.

RESULTS

Herein, a new probe TTM, containing thienothiophene and malononitrile units, was developed for exceptionally selective and sensitive hypochlorite (ClO-) detection. TTM demonstrated a rapid "turn-on" fluorescence response (<30 s), naked-eye detection (colorimetric), voltammetric read-out with anodic scan, low detection limit (LOD = 0.58 μM and 1.43 μM for optical and electrochemical methods, respectively) and applicability in detecting ClO- in real water samples and living cells.

SIGNIFICANCE AND NOVELTY

This study represents one of the rare examples of a small thienothiophene-based molecule for both optical and electrochemical detections of ClO- in an aqueous medium.