A near-infrared fluorescent probe for rapid detection of hydrogen peroxide in living cells

The first specific probe for pyrrolidine with multifunction by the interaction mechanism of atomic economic reaction

Pyrrolidine (PyD) has an important impact on the environment and human health. However, there is currently no method for trace detection of PyD. Here, we successfully designed diaminomethylene-4H-pyran (1) as the first specific fluorescent probe for PyD. Only by adding PyD to probe 1, there is blue fluorescence at 455 nm, and the color of the solution changes from colorless to yellow. The detection limit is 1.12 × 10-6 M, and the response time is less than 5 min. Meanwhile, probe 1 can also sense the gaseous PyD and detect PyD in actual water samples. Moreover, due to the low biological toxicity, probe 1 can detect the exogenous PyD in zebrafish. The preliminary mechanism shows that probe 1 and PyD undergo a combination-type chemical reaction to generate a new substance 1-PyD. Therefore, the 100% atom utilization reaction enables probe 1 to exhibit specific adsorption and removal of PyD.

Activatable Near-Infrared Versatile Fluorescent and Chemiluminescent Dyes Based on the Dicyanomethylene-4H-pyran Scaffold: From Design to Imaging and Theranostics

Activatable fluorescent and chemiluminescent dyes with near-infrared emission have indispensable roles in the fields of bioimaging, molecular prodrugs, and phototheranostic agents. As one of the most popular fluorophore scaffolds, the dicyanomethylene-4H-pyran scaffold has been applied to fabricate a large number of versatile activatable optical dyes for analytes detection and diseases diagnosis and treatment by virtue of its high photostability, large Stokes shift, considerable two-photon absorption cross-section, and structural modifiability. This review discusses the molecular design strategies, recognition mechanisms, and both in vitro and in vivo bio-applications (especially for diagnosis and therapy of tumors) of activatable dicyanomethylene-4H-pyran dyes. The final section describes the current shortcomings and future development prospects of this topic.

Fluorescence probes evaluated the hydrogen peroxide level in rice roots under cadmium ion stress

Abiotic stress and oxidative stress are closely related to the health status of plants. Plants will produce oxidative stress under abiotic stress, induce mitochondrial dysfunction, cause programmed cell death, and decrease plant survival rate. It is well known that rice is an essential crop for humans, but its cadmium tolerance is poor. Therefore, it is crucial to determine whether cadmium stress causes oxidative stress in rice in order to guide rice cultivation. Hydrogen peroxide (H2O2), a highly reactive oxygen species (ROS), is one of the most critical signals in corps under oxidative stress. In this work, we adopted a near-infrared (NIR) H2O2 fluorescent probe YFE-1 and a cadmium ion (Cd2+) fluorescent probe SCP to observe the fluctuation of H2O2 in rice roots under Cd2+ co-incubation conditions. Due to the advantages of fast response (within 2 min), a large Stokes shift (181 nm), good selectivity, and a low detection limit (LOD:26.4 nM), YFE-1 achieved the visualization of H2O2 produced by Cd2+ stress in rice roots. This study provides a new idea for assessing the risk of oxidative stress of Cd2+ in rice roots. It is expected to guide the control of Cd2+ in the rice planting industry to improve rice yield.

Novel selenium-containing photosensitizers for near-infrared fluorescence imaging-guided photodynamic therapy

Benzopyran nitrile dyes cannot be used as qualified photosensitizers due to the low quantum yield of triplet state. The benzopyran derivatives containing selenium instead of oxygen atom based on the heavy atom effect are expected to become potential agents for photodynamic therapy. In this paper, a series of selenium-containing photosensitizers (PS_X) were prepared according to this strategy. PS_X can effectively produce both singlet oxygen and superoxide anions upon laser irradiation. PS_X exhibited the emission wavelength at 500-800 nm and near-infrared (NIR) fluorescence imaging in HeLa cells. Excellent biocompatibility and phototoxicity further indicated that PS_X could be used as efficient photosensitizers for NIR fluorescence imaging and photodynamic therapy.

Boronate-Based Fluorescent Probes as a Prominent Tool for H2O2 Sensing and Recognition

Given the crucial association of hydrogen peroxide with a wide-range of human diseases, this compound has currently earned the reputation of being popular biomolecular target. Although various of analytical methods have attracted our attention, fluorescent probes have been used as prominent tools to determine H2O2 to reflect the physiological and pathological conditions of biological systems, As the sensitive responsive portion of these probes, Boronate ester and boronic acid groups are vital reporter as the sensitive responsive part for H2O2 recognition. In this review, we summarized boronate ester/boronic acid group-based fluorescent probes for H2O2 reported from 2012 to 2020 and generally classify the fluorophores into six categories to exhaustively elaborate the design strategy and comprehensive systematic performance. We hope that this review will inspire the exploration of new fluorescent probes based on boronate ester/boronic acid groups for detection of H2O2 and other relevant analytes.

Enhanced cellular uptake efficiency of DCM probes or SN38 conjugating with phenylboronic acids

High-level of sialic acid (SA) expression on the surface of cancer cells is observed extremely common. Phenylboronic acids (PBAs) have a high affinity with SA. The cellular uptake efficiency could be enhanced by the strategy of introducing PBA fragments to the compounds. In this work, we synthesized five new probes with the Dicyanomethylene-4H-pyran (DCM) fluorophore, three of them conjugated with different phenylboronic acid fragments. By cellular uptake experiments, DLCB and DLAB showed enhanced cellular uptake abilities compared with DLN and DLO. These two effective phenylboronic acid fragments were then conjugated with SN-38 and the conjugates showed enhanced cellular uptake abilities by 3-fold or 7-fold compared with irinotecan. In summary, the strategy of introducing 4-carboxyphenylboronic acid and 3-amino-benzoxaborole groups shows great potential in drug delivery system. Moreover, the released linkers between boric acid and drugs deserve further studies.

A near-infrared fluorescent probe based on boric acid hydrolysis for hydrogen peroxide detection and imaging in HeLa cells

Using the characteristics of hydrogen peroxide that are able to cleave phenyl-boric acid selectively and efficiently, we here report a dicyanoisophorone-boric acid (DCP-BA)-based near-infrared (NIR) fluorescent probe for detection of hydrogen peroxide. This probe shows a rapid, highly selective, and sensitive detection process for hydrogen peroxide with a significant NIR fluorescent turn-on response that has been successfully applied to detect exogenous hydrogen peroxide in HeLa cells.

A near-infrared fluorescent probe for rapid detection of carbon monoxide in living cells

A near-infrared (NIR) and colorimetric fluorescent probe system was developed for Carbon Monoxide (CO) via a Pd⁰-mediated Tsuji-Trost reaction. In this probe, phenoxide anion formation (DPCO^-) was acted as the signal unit and an allyl carbonate group was used as the recognition unit. This non-fluorescent probe molecule can release the relevant fluorophore after conversion of Pd²⁺ to Pd⁰ by CO. The probe system including probe 1 and Pd²⁺ can be used for "naked-eye" detection of CO, and exhibited high selectivity to CO over various other sensing objects. More importantly, the probe system has great potential for fluorescence imaging of intracellular CO in living cells.

Recent advances of dicyano-based materials in biology and medicine

We highlight the development of dicyano-based fluorescent materials in biology and medicine.

A new ratiometric fluorescent probe for detecting endogenous HClO in living cells

A new benzimidazole-hemicyanine-based ratiometric fluorescent probe (ZBM-H) was developed, which showed high selectivity and sensitivity for detecting HClO.

Near-Infrared Dioxetane Luminophores with Direct Chemiluminescence Emission Mode

Chemiluminescent luminophores are considered as one of the most sensitive families of probes for detection and imaging applications. Due to their high signal-to-noise ratios, luminophores with near-infrared (NIR) emission are particularly important for in vivo use. In addition, light with such long wavelength has significantly greater capability for penetration through organic tissue. So far, only a few reports have described the use of chemiluminescence systems for in vivo imaging. Such systems are always based on an energy-transfer process from a chemiluminescent precursor to a nearby emissive fluorescent dye. Here, we describe the development of the first chemiluminescent luminophores with a direct mode of NIR light emission that are suitable for use under physiological conditions. Our strategy is based on incorporation of a substituent with an extended π-electron system on the excited species obtained during the chemiexcitation pathway of Schaap's adamantylidene-dioxetane probe. In this manner, we designed and synthesized two new luminophores with direct light emission wavelength in the NIR region. Masking of the luminophores with analyte-responsive groups has resulted in turn-ON probes for detection and imaging of β-galactosidase and hydrogen peroxide. The probes' ability to image their corresponding analyte/enzyme was effectively demonstrated in vitro for β-galactosidase activity and in vivo in a mouse model of inflammation. We anticipate that our strategy for obtaining NIR luminophores will open new doors for further exploration of complex biomolecular systems using non-invasive intravital chemiluminescence imaging techniques.

A fluorogenic and red-shifted diphenyl phosphinate-based probe for selective peroxynitrite detection as demonstrated in fixed cells

A new dicyanomethylene-4H-pyran-based fluorescent probe has been designed, synthesized and characterized. It shows selective “TURN-ON” fluorescence response upon reaction with ONOO⁻.

Selective turn-on near-infrared fluorescence probe for hypoxic tumor cell imaging

In this study, we designed a new selective turn on near-infrared fluorescence probe by conjugating (1-methyl-2-nitro-1H-imidazol-5-yl)methanol to DCPO with ether linkage for hypoxic tumor cell imaging.

A smart upconversion-based light-triggered polymer for synergetic chemo-photodynamic therapy and dual-modal MR/UCL imaging

We have developed a novel nanocomposite to achieve effective therapy and live surveillance of tumor tissue. In this study, fullerene (C₆₀) with iron oxide (Fe₃O₄) nanoparticles and upconversion nanophosphors (UCNPs) was loaded into N-succinyl-N'-4-(2-nitrobenzyloxy)-succinyl-chitosan micelles (SNSC) with good biocompatibility. In addition, hydrophobic anticancer drug docetaxel (DTX) was also loaded into the nanocomposites. The experiments conducted in vitro and in vivo demonstrated that C₆₀/Fe₃O₄-UCNPs@DTX@SNSC can act synergistically to kill tumor cells by releasing chemotherapy drugs at specific target site as well as generating reactive oxygen using 980nm. In addition, it can also be used for non-invasive deep magnetic resonance and upconversion fluorescence dual-mode imaging. The results indicated that this system provided an efficient method to surmount the drawback of UV or visible light-responsive polymeric systems for controlled drug release and generated reactive oxygen in deep tissues and ultimately realized the integration of dual-modal imaging and treatment.

NIR fluorescent DCPO glucose analogues and their application in cancer cell imaging

N3-DCPO and its glucose analogues were synthesized, and the linker's length impact on cellular uptake was studied.

DCPO based nanoparticles as a near-infrared fluorescent probe for Cathepsin B

In this article we designed a Cathepsin B-sensitive near-infrared fluorescent probe which can self-assemble into nano-micelles.