Tetraphenylethylene–thiosemicarbazone based ultrafast, highly sensitive detection of hypochlorite in aqueous environments and dairy products

A novel AIE-based mitochondria-targeting fluorescent probe for monitoring of the fluctuation of endogenous hypochlorous acid in ferroptosis models

Ferroptosis is a way of cell death mainly due to the imbalance between the production and degradation of lipid reactive oxygen species, which is closely associated with various diseases. Endogenous hypochlorous acid (HOCl) mainly produced in mitochondria is regarded as an important signal molecule of ferroptosis. Therefore, monitoring the fluctuation of endogenous HOCl is beneficial to better understand and treat ferroptosis-related diseases. Inspired by the promising aggregation-induced emission (AIE) properties of tetraphenylethene (TPE), herein, we rationally constructed a novel AIE-based fluorescent probe, namely QTrPEP, for HOCl with nice mitochondria-targeting ability and high sensitivity and selectivity. Probe QTrPEP consisted of phenylborate ester and the AIE fluorophore of quinoline-conjugated triphenylethylene (QTrPE). HOCl can brighten the strong fluorescence through a specific HOCl-triggered cleavage of the phenylborate ester bond and release of QTrPE, which has been demonstrated by MS, HPLC, and DLS experiments. In addition, combining QTrPE-doped test strips with a smartphone-based measurement demonstrated the excellent performance of the probe to sense HOCl. The obtained favorable optical properties and negligible cytotoxicity allowed the use of this probe for tracking of HOCl in three different cells. In particular, this work represents the first AIE-based mitochondria-targeting fluorescent probe for monitoring the fluctuation of HOCl in ferroptosis.

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.

Construction of optical dual-mode sensing platform based on green emissive carbon quantum dots for effective detection of ClO- and cellular imaging

Hypochlorite (ClO-) is an important redox regulator in reactive oxygen species, which play a considerable role in oxidative stress and related diseases. Hence, accurate and sensitive monitoring of ClO- concentration was urgently needed in the fields of life sciences, food and environment. Bright green fluorescent carbon quantum dots (G-CQDs) were synthesized utilizing one-step hydrothermal method with citric acid and acriflavine precursors. Through TEM, FTIR, XPS and zeta potential characterization procedures, G-CQDs illustrated uniformly dispersed and significant number of -NH2 and -OH on the surface. Meanwhile, the fluorescence and colorimetric analysis exhibited wide linear range and low detection limit response to ClO-. The fluorescence changes of G-CQDs were identified via smartphone to realize mobile sensing of ClO-. Subsequently, G-CQDs was applied for visualization and quantitative detection of ClO- in drinking water samples with satisfactory recovery rate. More importantly, G-CQDs demonstrated good water solubility, optical stability and excellent biocompatibility, which offered a promising analysis approach in cell imaging and exogenous ClO- detection in living cells. G-CQDs illustrated bright prospect and great potential in practical application of ClO- associated disease prevention and early clinical diagnosis.

A Commercially Available 2-aminoanthracene Fluorescent Probe for Rapid and Sensitive Detection of Hypochlorite in 100% Buffer Solution and its Application in Complex Water Samples

Hypochlorite (ClO-), a crucial chemical in the living organism, engages in various physiological activities. However, high amounts of ClO- result in oxidative damage. In this work, a commercially available 2-aminoanthracene (AA) was used to detect ClO-. AA demonstrated distinct properties such as superior selectivity and rapid response (< 30 s) with a low detection limit (140 nM) towards ClO- in 100% buffer solution. Furthermore, the probe exhibited a notable achievement by effectively identifying the presence of ClO- in complicated water samples. In conclusion, AA offers an easy-to-use and accurate method for quantifying ClO- in complex water samples.

New Fluorophore and Its Applications in Visualizing Polystyrene Nanoplastics in Bean Sprouts and HeLa Cells

In the domain of environmental science, pollutants of nanoscale plastic dimensions are acknowledged as subjects of intricate significance. Such entities, though minuscule, present formidable challenges to ecological systems and human health. The diminutive dimensions of these contaminants render their detection arduous, thus demanding the inception of avant-garde methodologies. The present manuscript postulates the employment of the tetraphenylethylene functional group with a fused xanthene (TPEF), a distinguished fluorophore, as an exemplary system for the discernment of nanoplastic particulates. The synthesis and characterization of TPEF have been exhaustively elucidated, revealing its paramount fluorescence attributes and inherent affinity for interaction with nanoplastics. When subjected to comparison with TPEF, nanoplastics are observed to manifest a more pronounced fluorescent luminescence than when associated with the conventional Nile Red (NR). Particularly, the TPEF has shown exceptional affinity for polystyrene (PS) nanoplastics. Further, the resilience of nanoplastics within the hypocotyl epidermis of soybeans, as well as their persistence in mung bean sprouts subsequent to rigorous rinsing protocols, has been meticulously examined. Additionally, this investigation furnishes empirical data signifying the existence of nano-dimensional plastic contaminants within HeLa cellular structures. The urgency of addressing the environmental ramifications engendered by these diminutive yet potent plastic constituents is emphatically highlighted in this manuscript. TPEF paves the way for prospective explorations, with the aspiration of devising efficacious mitigation strategies. Such strategies might encompass delineating the trajectories undertaken by nanoplastics within trophic networks or their ingress into human cellular architectures.

Monitoring of Hypochlorite Level in Fruits, Vegetables, and Dairy Products: A BODIPY-Based Fluorescent Probe for the Rapid and Highly Selective Detection of Hypochlorite

Hypochlorite/hypochlorous acid (ClO^-/HOCl), among the diverse reactive oxygen species, plays a vital role in various biological processes. Besides, ClO^- is widely known as a sanitizer for fruits, vegetables, and fresh-cut produce, killing bacteria and pathogens. However, excessive level of ClO^- can lead to the oxidation of biomolecules such as DNA, RNA, and proteins, threatening vital organs. Therefore, reliable and effective methods are of utmost importance to monitor trace amounts of ClO^-. In this work, a novel BODIPY-based fluorescent probe bearing thiophene and a malononitrile moiety (BOD-CN) was designed and constructed to efficiently detect ClO^-, which exhibited distinct features such as excellent selectivity, sensitivity (LOD = 83.3 nM), and rapid response (<30 s). Importantly, the probe successfully detected ClO^- in various spiked water, milk, vegetable, and fruit samples. In all, BOD-CN offers a clearly promising approach to describe the quality of ClO^--added dairy products, water, fresh vegetables, and fruits.

Highly sensitive fluorescent probes for selective detection of hypochlorite: Applications in blood serum and cell imaging

Being one of the vital reactive oxygen species (ROS), abnormal level of hypochlorite ion (ClO^-) may pose detrimental threats to living organisms. Therefore, highly selective, and rapid monitoring of ClO^- in living system is of prime importance to protect living organisms from its harmful effects. In this regard, design of synthetic fluorescent probes for ClO^- has garnered considerable attention. However less fluorescence emission in aggregated state and less photostability of several existing probes for ClO^- inspired us to design aggregation induced emission (AIE) active fluorescent probes SH1 and SH2. Probes were rationally designed by introducing thiourea moiety that selectively reacted through desulfurization reaction and resulted in highly selective detection of ClO^-. Hypochlorite induced desulfurization reaction was validated through ¹H NMR titration and DFT studies. Fine tuning of probes SH1 and SH2 prompted highly sensitive nanoscale (55 nM and 77 nM) and rapid (15 and 35 sec) detection of ClO^-. Probe SH1 displayed less cytotoxic effect to live cells before it was successfully applied for bioimaging of ClO^- in live MCF-7 cells. Moreover, probes displayed excellent sensing potential for ClO^- in blood serum and real water samples. Advantageously, probe coated portable fluorescent films were fabricated for the easy and fast monitoring of ClO^-. Of note, this work offers excellent design strategy for highly selective detection of ClO^- that may lead to clinical trials.

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.

An Anthracene and Indole-based Fluorescent Probe for the Detection of Chromium(III) Ions in Real Water Samples

A novel fluorescent probe possessing anthracene with an indole unit was designed and synthesized to detect chromium(III) ions (Cr³⁺) with high sensitivity and selectivity. The probe was synthesized in one step by mixing two commercially available chemicals, 2-aminoanthracene and Indole-5-carboxaldehyde. The probe molecule (ANT-In) demonstrates distinct properties, for instance, "turn-on" fluorescence response, high sensitivity and selectivity in less than one minute, and low detection limit (0.2 µM) via hydrolysis of the C = N bond. Additionally, the probe ANT-In was successfully used to identify the presence of chromium(III) ions in real water samples.

Combining tetraphenylethene (TPE) derivative cations with Eu3+-β-diketone complex anions for tunable luminescence

Tetraphenylethene (TPE) derivative cations (TPE⁺) and Eu³⁺-β-diketone complex anions (Eu(ABM)₄^-) were combined to construct a novel dual energy transfer system (TPE⁺ to Eu³⁺ and ABM to Eu³⁺). Our system exhibits tunable luminescence in DMF/water mixtures under different f_w conditions owing to the AIE and ACQ properties of TPE⁺ and ABM, respectively. Its luminescence can be also regulated by adding P-containing oxysalts or polyacrylic acids.

Multiresponsive tetrarylethylene-based fluorescent dye with multicoloreded changes: AIEE properties, acidichromism, Al3+ recognition, and applications

A novel fluorescent sensor BTAE-PA containing two tetrarylethylene (TAE) units linked through pyrimidine-2-amine was prepared, and its optical properties were systematically studied. BTAE-PA exhibited a typical aggregation-induced emission enhancement behavior, and its fluorescent properties could be efficiently modulated by acid/base and metal ions in THF. The protonated effect could induce significant acidichromism and 'turn-on' near-infrared emission with a large Stokes shift (Δλ = 225 nm). Furthermore, BTAE-PA was highly selective toward Al³⁺ with significant absorption (yellow → orange) and fluorescence (green → red) changes. A Job's plot established the 1 : 1 stoichiometry of the complex formation between BTAE-PA and Al³⁺, and the limit of detection for Al³⁺ was determined to be 1.30 × 10^-7 mol L^-1. Finally, we also demonstrated that BTAE-PA could be made into test paper strips for 'naked-eye' detection of acid/Al³⁺, and fluorescence imaging experiments proved that BTAE-PA is capable of achieving cell imaging with good biocompatibility. Therefore, the multi-stimuli-responsive and multicoloured display performance of BTAE-PA endows the material with potential applications in security ink, acid/Al³⁺ sensing, and bio-imaging.