A mitochondria-targeted fluorescent probe for real-time imaging SO2/H2O2

Construction of a dual-excitation ratiometric fluorescent probe for determining peroxynitrite levels in living cells and zebrafish

Peroxynitrite (ONOO-) is a highly reactive oxygen species that plays a critical role in many physiological and pathological processes of cell function. This study aimed to propose a ratiometric fluorescent probe BDHCA derived from coumarin for determining the ONOO- level. ONOO- could specifically induce oxidative cleavage of the conjugated C = C double bond in probe BDHCA, providing a fluorescent ratiometric output. The response of probe BDHCA to ONOO- was selective, fast, and highly sensitive, with a detection limit of 50.3 nM. Biological imaging experiments suggested that probe BDHCA could be used to image ONOO- in living RAW264.7 cells and zebrafish.

Preparation of copper nanoparticles fluorescent probes and detection of hydrogen peroxide and glucose

Fluorescent copper nanoparticles (CuNPs) was synthesized by one-step chemical reduction method using ascorbic acid (AA) and copper sulfate (CuSO4⋅5H2O) as raw materials, which had good water solubility and fluorescence properties. A green, simple and safe CuNPs@Fe2+ fluorescence probe was developed for the detection of hydrogen peroxide and glucose using Fe2+ as a bridge. The prepared CuNPs could obtain the maximum fluorescence emission wavelength at 440 nm when the excitation wavelength was 360 nm. The average particle size of CuNPs was 10 nm, which had good photobleach resistance, stability and salt tolerance. The fluorescence intensity was quenched due to electron transfer (ET) process when hydrogen peroxide was added to CuNPs@Fe2+ system. This result was mainly because Fenton reaction occured between hydrogen peroxide and Fe2+, producing hydroxyl free radicals (OH) and Fe3+. Since glucose could be catalyzed by specific glucose oxidase (GOX) to produce H2O2 and corresponding oxidation products, the quantitative analysis of glucose was realized when glucose oxidase was introduced into the CuNPs@Fe2+ sensor system. Therefore, a novel CuNPs@Fe2+ fluorescent probe sensor study was constructed to further achieve quantitative detection of H2O2 and glucose. Under the optimized experimental conditions, the linear ranges for H2O2 and glucose were 28.219-171.562 μM and 1.237-75.771 μM, respectively. And the detection limits for H2O2 and glucose were 7.169 μM and 0.540 μM, respectively. In addition, the mechanism of fluorescence probe quenching caused by the interaction between H2O2 and CuNPs@Fe2+ was also discussed. The proposed sensing system had been applied successfully to the detection of glucose in human serum samples.

An overview on recent advances of reversible fluorescent probes and their biological applications

Due to the simplicity and low detection limit, fluorescent probes are widely used in both analytical sensing and optical imaging. Compared to conventional fluorescent probes, reversibility endows the reversible fluorescent probe outstanding advantages and special properties, making reversible fluorescent probes with capable of quantitative, repetitive or circulatory. Reversible fluorescent probes can also monitor the concentration dynamics of target analytes in real time, such as metal ions, proteins and enzymes, as well as intracellular redox processes, which have been widely applied in various fields. This review summarized the types and excellent properties of reversible fluorescent probes designed and developed in recent years. It also summarized the applications of reversible fluorescent probe in fluorescence imaging, biological testing, monitoring redox cycles, and proposed the remaining challenges and future development directions of the reversible fluorescent probe. This review provided comprehensive overview of reversible fluorescent probe, which may provide valuable references for the design and fabrication of the reversible fluorescent probe.

A multifunctionally reversible detector: Photoacoustic and dual-channel fluorescence sensing for SO2/H2O2

In this work, the phenothiazine fragment with powerful electron-donating ability was specifically selected to construct a multifunctional detector (noted as T1) in double-organelle with near-infrared region I (NIR-I) absorption. The changes of SO₂/H₂O₂ content in mitochondria and lipid droplets were observed through red/green channels respectively, which was due to the reaction between benzopyrylium fragment of T1 and SO₂/H₂O₂ to achieve red/green fluorescence conversion. Additionally, T1 was endowed with photoacoustic properties deriving from NIR-I absorption to reversibly monitor SO₂/H₂O₂in vivo. This work was significant for more accurately deciphering the physiological and pathological processes in living organisms.

A red fluorescence probe for reversible detection of HSO3-/H2O2 and its application in food samples and bioimaging

Reducing agent SO₂ and oxidant H₂O₂ are two essential substances in cells, and the balance between them is closely related to the survival of cells. SO₂ derivative HSO₃^- is often used as food additive. Therefore, simultaneous detection of SO₂ and H₂O₂ is of great significance in biology and food safety. In this work, we successfully developed a mitochondria-targeted red fluorescent probe (HBTI), which has excellent selectivity, high sensitivity and large Stokes shift (202 nm). HBTI and HSO₃^-/SO₃^2- undergo Michael addition on the unsaturated C=C bond, and the addition product (HBTI-HSO₃^-) can react with H₂O₂ to restore the conjugated structure. Fluorescence changes from red to non-emissive and then restores to red, and can be detected quickly and visually. In addition, HBTI has been successfully targeted mitochondria, and achieved dynamic reversible response to SO₂/H₂O₂ in living cells, and has been successfully applied to detect SO₂ in food samples.

A coumarin-based fluorescent probe: single-wavelength excitation, discrimination of Cys/Hcy and GSH by naked eyes

Biothiols mainly include cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), which play an important role in life activities and abnormal changes in their concentrations are closely related to certain diseases. Therefore, the quantitative tracking and analysis of biothiols in living organisms has become a hot research topic in recent years. In this work, a coumarin-based fluorescent probe COUN was designed and synthesized for the comparable color recognition of Cys/Hcy and GSH by introducing the phenylethynyl group as the recognition site of biothiols, which showed significant fluorescence enhancement and green fluorescence under the UV light at 365 nm. The probe specifically recognized Hcy, showing 40-fold fluorescence enhancement and strong green fluorescence at 492 nm. Moreover, there was a good linear relationship between the fluorescence intensity of the probe and certain concentrations of Cys/Hcy and GSH, with detection limits of 36.6 nM, 86.4 nM, and 174 nM, respectively. The recognition mechanism of COUN to distinguish Cys/Hcy and GSH was studied by TDDFT calculations. More importantly, COUN was successfully used for imaging biothiols in living cells. The results showed that this probe could provide an effective contribution to the understanding of the role of biothiols, especially Hcy.

Coumarin-cyanine hybrid: A ratiometric fluorescent probe for accurate detection of peroxynitrite in mitochondria

There is an urgent need to develop highly sensitive and selective fluorescence probes for ONOO^- in mitochondria. Herein, we reported a ratiometric fluorescent probe COUS with coumarin-cyanine hybrid as fluorophore and C = C bonds as reaction sites of ONOO^-. The probe COUS was sensitive and selective to ONOO^-, and had a large fluorescence emission shift (239 nm) as well as a low detection limit (41.88 nM). Moreover, COUS showed the mitochondrial targeting ability, and the targeting moiety could dissociate from the probe when reacting with ONOO^-, which enabled COUS to accurately detect ONOO^- in mitochondria.

Reversible colorimetric and NIR fluorescent probe for sensing SO2/H2O2 in living cells and food samples

Preservative sulfur dioxide (SO₂) and bleach hydrogen peroxide (H₂O₂) were widely used in the food industry, at the same time, they were also a redox pair in biological systems. Therefore, the reversible sensing SO₂/H₂O₂ was of great significance in food safety and biology. In this paper, a colorimetric and NIR fluorescent dual channels response probe (DCA-Bba) for SO₂/H₂O₂ based on chromene-barbiturate was developed. DCA-Bba exhibited a rapid and sensitive recognition of SO₂, and the adduct DCA-Bba-HSO₃^- could detect H₂O₂ in PBS (with 10 % DMSO, v/v, pH 7.4) solution. The reversible response of DCA-Bba was implemented by HSO₃^- involved 1,4-addition and H₂O₂ induced elimination reaction. DCA-Bba showed a strong red fluorescence based on the intramolecular charge transfer (ICT) process, after the recognition of SO₂, the fluorescence of the adduct was quenched based on the photoinduced electron transfer (PET) process. And importantly, DCA-Bba had been applied for imaging SO₂/H₂O₂ redox cycles in living cells, as well as could detect the levels of SO₂ in white sugar, biscuit, Chinese liquor and red wine samples.

A ratiometric ESIPT fluorescent probe for detection of anticancer-associated H2O2 level in vitro and in vivo

ROS is a significant factor in the cancer treatment mechanism. The monitoring anticancer-associated H₂O₂ level plays a vital role in the anticancer mechanistic exploration in pathology and physiology. Herein we synthesized a ratiometric fluorescent probe (HBQ-L) to detect and image H₂O₂ based on excited-state intramolecular proton transfer. HBQ-L had a high sensitivity (231-fold) with a low detection limit (28.5 nM) for monitoring H₂O₂ in solution. HBQ-L showed good mitochondrial-targeting and successfully detected both exo-/endogenous H₂O₂ in A549 cells. Furthermore, HBQ-L was used to ratiometric monitor H₂O₂ level in anticancer reagent DOX-treated cells or zebrafish. Importantly, it was employed to access the monitoring H₂O₂ in the A549 tumor-bearing mice.

Enhancing probe's sensitivity for peroxynitrite through alkoxy modification of dicyanovinylchromene

An intramolecular charge transfer (ICT)-based fluorescent probe P-ONOO^- was synthesized to detect ONOO^-. After responding to peroxynitrite, the dicyano-vinyl group of P-ONOO^- generates the aldehyde group, emitting strong green fluorescence accompanied by quenching of the yellow fluorescence. According to the calculated Fukui function, the modification of the alkoxy group can enhance the f⁺ of P-ONOO^-, which can enhance the probe's nucleophilic addition reactivity with ONOO^-. It has been experimentally verified that P-ONOO^- shows fast response (within 30 s), excellent sensitivity (the detection limit = 10.4 nM), and good selectivity towards ONOO^-. Additionally, the probe P-ONOO^- has high membrane permeability and good biocompatibility, which can image endogenous ONOO^- and exogenous ONOO^- in HeLa cells.

A new near-infrared fluorescence probe synthesized from IR-783 for detection and bioimaging of hydrogen peroxide in vitro and in vivo

A new near-infrared fluorescence probe was developed and synthesized for detection of hydrogen peroxide (H₂O₂) in vitro and in vivo. Synthesized from IR-783, the probe DBIS was designed to connect 4-(Bromomethyl)benzeneboronic acid pinacol ester as the recognizing moiety to the stable hemicyanine skeleton. Reaction of probe DBIS with H₂O₂ would result in the oxidation of phenylboronic acid pinacol ester, and thereby release the near-infrared fluorophore HXIS. The background signal of probe DBIS is very low, which is necessary for sensitive detection. Compared with the existing probes for detecting H₂O₂, the proposed probe DBIS shows excellent optical performance in vitro and in vivo, high selectivity, high sensitivity and good water solubility, as well as near-infrared fluorescence emission 708 nm, with a low detection limit of 0.12 μM. Furthermore, probe DBIS is low cytotoxic, cell membrane permeable, and its applicability has been shown to visualize endogenous H₂O₂ in mice. In addition, it is the first time that paper chips have been used as carrier to detect H₂O₂ through fluorescence signals instead of the traditional liquid phase detection mode of fluorescent probes. These superior characteristics of the probe make it have great application potential in biological systems or in vivo related research.