A novel borate fluorescent probe for rapid selective intracellular peroxynitrite imaging

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.

Near-infrared molecular sensor for visualizing and tracking ONOO- during the process of anti-tuberculosis drug-induced liver damage

Isoniazid (INH) and pyrazinamide (PZA) are both the first-line anti-tuberculosis drugs in clinical treatment. It is notable that there are serious side effects of the drugs along with upregulation of reactive nitrogen species, mainly including peripheral neuritis, gastrointestinal reactions, and acute drug-induced liver injury (DILI). Among them, DILI is the most common clinical symptom as well as the basic reason of treatment interruption, protocol change, and drug resistance. As vital reactive nitrogen species (RNS), peroxynitrite (ONOO-) has been demonstrated as a biomarker for evaluation and pre-diagnosis of drug-induced liver injury (DILI). In this work, we developed a red-emitting D-π-A type fluorescence probe DIC-NP which was based on 4'-hydroxy-4-biphenylcarbonitrile modified with dicyanoisophorone as a fluorescent reporter and diphenyl phosphinic chloride group as the reaction site for highly selective and sensitive sensing ONOO-. Probe DIC-NP displayed a low detection limit (14.9 nM) and 60-fold fluorescent enhancement at 669 nm in the sensing of ONOO-. Probe DIC-NP was successfully applied to monitor exogenous and endogenous ONOO- in living HeLa cells and zebrafish. Furthermore, we verified the toxicity of isoniazid (INH) and pyrazinamide (PZA) by taking the oxidative stress induced by APAP as a reference, and successfully imaged anti-tuberculosis drug-induced endogenous ONOO- in HepG2 cells. More importantly, we developed a series of mice models of liver injury and investigated the hepatotoxicity caused by the treatment of anti-tuberculosis drugs. At the same time, H&E of mice organs (heart, liver, spleen, lung, kidney) further confirmed the competence of probe DIC-NP for estimating the degree of drug-induced liver injury, which laid a solid foundation for medical research.

A dihydro-benzo[4,5]imidazo[1,2-c]quinazoline-based probe with aggregation-induced ratiometric emission for the ratiometric fluorescent detection of peroxynitrite in living cells and zebrafish

As a significant kind of reactive oxygen species (ROS), peroxynitrite (ONOO-) plays an indispensable role in many physiological and pathological processes. This study aimed to synthesize a novel dihydro-benzo[4,5]imidazo[1,2-c]quinazoline-based probe 1 for detecting ONOO-. In 99.5% H2O solution, probe 1 displayed a distinct aggregation-induced ratiometric emission (AIRE), and would selectively respond toward ONOO-via a ratiometric fluorescent signal, along with a short response time (<30 s) and ultra-sensitivity (LOD = 17.6 nM). Moreover, the probe was applied for monitoring the concentration fluctuations of ONOO- in HeLa cells and zebrafish.

Recent Progress of Spectroscopic Probes for Peroxynitrite and Their Potential Medical Diagnostic Applications

Peroxynitrite (ONOO-) is a crucial reactive oxygen species that plays a vital role in cellular signal transduction and homeostatic regulation. Determining and visualizing peroxynitrite accurately in biological systems is important for understanding its roles in physiological and pathological activity. Among the various detection methods, fluorescent probe-based spectroscopic detection offers real-time and minimally invasive detection, high sensitivity and selectivity, and easy structural and property modification. This review categorizes fluorescent probes by their fluorophore structures, highlighting their chemical structures, recognition mechanisms, and response behaviors in detail. We hope that this review could help trigger novel ideas for potential medical diagnostic applications of peroxynitrite-related molecular diseases.

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.

Colorimetric and fluorescent dual-signals probes for naked-eye detection of hydrogen peroxide and applications in milk samples and in vivo

Excessive residual hydrogen peroxide (H₂O₂) disinfectant in food is harmful to human health. Therefore, it is necessary to develop efficient detection methods for H₂O₂ detection. In this work, we designed and synthesized five D-A molecules 3a-3e by introducing electron-donor substituents (-OCH₃ and -CH₃) to the electron-acceptor dicyanoisophorone skeleton in order to find out the suitable probes for H₂O₂ detection. Among them, two promising probes, 3a and 3c, are screened out according to structure-property relationships. Based on the principle of intramolecular charge transfer (ICT), 3a and 3c express colorimetric and fluorescent dual-signals towards H₂O₂ with low detection limits (0.20 μM and 0.14 μM) and rapid response (within 20 mins). The reaction mechanism between probes and H₂O₂ is determined by ¹H NMR and HRMS. Density functional theory (DFT) calculations are measured to study the regulation mechanism of structure adjustment on probs performance. Furthermore, a smartphone RGB analysis is utilized as a portable platform for the quantitative detection of H₂O₂ without complicated instruments, indicating a high efficiency and on-site detection method for H₂O₂. In addition, probes are applied to detect H₂O₂ in milk samples, HepG-2 cells and zebrafish, suggesting the promising applications in food samples and physiological systems.

Regulating the activity of boronate moiety to construct fluorescent probes for the detection of ONOO-in vitro and in vivo

Abnormal intracellular peroxynitrite (ONOO^-) concentration is related to oxidative damage, which is correlated with many pathological consequences, such as local inflammation and other diseases. In this work, a series of resorufin benzyl ether-based fluorescent probes were designed using boronate as a recognizing moiety installed on a phenyl moiety for ONOO^- detection via a self-immolation mechanism. The location of the boronate as well as the substitution patterns on the phenyl moiety were investigated and the responding behaviors of the designed probes to ONOO^-, other reactive oxygen species, and biothiols were examined. It was found that all the immolative probes were inevitably dominated by ONOO^-. Compared with other probes, p-Borate possessed favorable selectivity and high sensitivity to ONOO^-. Moreover, p-Borate was successfully used to detect ONOO^- in cells and inflamed mice.

Unveiling the effects of atomic electronegativity on the ESIPT mechanism and luminescence property of new coumarin benzothiazole Fluorophore: A TD-DFT exploration

The excited-state intramolecular proton transfer (ESIPT) mechanism, photophysical properties of 8-(benzo[D] thiazole-2-yl)-7-hydroxy-2H-benzopyran-2-one (L-HKS) and the effect of O/Se atomic substitution on L-HKS have been studied in detail based on density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. The S atom in the thiazole ring of L-HKS has been replaced by O/Se atom (denoted to L-HKO/L-HKSe) to analyze the effects of atomic electronegativity on the intramolecular H-bond, absorption/emission spectrum and ESIPT process. Through the analysis of series of calculated results, it can be found that the intramolecular H-bonds at normal form and tautomer form are enhanced and weakened in the S₁ state, respectively, which is favorable to ESIPT process. The potential energy curves revealed that the ESIPT process is much easier to occur gradually from L-HKO to L-HKS and L-HKSe, as the electron-withdrawing ability of atom (from O to S and Se) is weakened. The atomic substitution also has an effect on the photophysical properties. From L-HKO to L-HKS, the emission peak at tautomer form red-shifts 70 nm. The energy gaps of the three compounds follow the decreased order of L-HKO (4.866 eV) > L-HKS (4.753 eV) > L-HKSe (4.371 eV) with the weakened electron-withdrawing ability of atom (from O to S and Se), which leads to the gradual red-shift of the absorption spectra from L-HKO to L-HKS and L-HKSe.

Fullerenol protects cornea from ultraviolet B exposure

The eyes are highly susceptible to the oxidative stress induced by ultraviolet B (UVB, wavelength between 280 ∼ 320 nm), which could cause severe damage to the cornea. Fullerenols are effective antioxidants to alleviate UVB-induced injury, while their application for the eyes is still rare. In present study, we investigated the protective performance and mechanism of fullerenols on cornea under UVB radiation in vivo and in vitro. The synthesized fullerenols exhibited broad-spectrum free radical scavenging properties (applicable to both reactive oxygen species (ROS) and reactive nitrogen species (RNS)) and photo-stability. When compared with another widely used antioxidant glutathione (GSH), the administration of fullerenols markedly decreased the injured area, corneal edema, cell death, and increased the cell proliferation in UVB-induced rat cornea. The effects of fullerenols were confirmed in UVB-exposed human corneal epithelial cells (hCECs), where elevated cell viability and proliferation, decreased oxidative free radical production, repaired mitochondrial dysfunction and DNA lesions were observed. RNA sequencing (RNA-Seq) analysis demonstrated that fullerenol alleviated UVB-induced corneal injury through down-regulation of oxidative stress-related genes and up-regulation of proliferation-associated genes. Our results demonstrate the suitability of fullerenols as a potential exogenous treatment in ameliorating UVB-induced cornea damage.

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Fullerenol produces significant precaution on UVB-induced corneal damage.

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Fullerenol exhibits broader spectrum free radical scavenging properties than GSH.

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Fullerenol mitigates the LSCs loss in the cornea caused by UVB.

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Fullerenol down-regulates oxidative stress genes and up-regulates proliferation-related genes.

Construction of a mitochondria-endoplasmic reticulum dual-targeted red-emitting fluorescent probe for imaging peroxynitrite in living cells and zebrafish

Peroxynitrite (ONOO - ) is one of the important reactive oxygen species, which plays a vital role in the physiological process of intracellular redox balance. Revealing the biological functions of ONOO - will contribute to further understanding of the oxidative process of organisms. In this work, we designed and synthesized a novel red-emitting fluorescent probe MCSA for the detection of ONOO - , which could rapidly respond to ONOO - within 250 s and exhibited high sensitivity to ONOO - with a low detection limit of 78 nM. Co-localization experiments demonstrated MCSA had the ability to localize into the mitochondria and endoplasmic reticulum. What's more, MCSA enabled monitoring ONOO - level changes during tunicamycin-induced endoplasmic reticulum stress. We have also successfully achieved the visual detection of exogenous and endogenous ONOO - in living cells and zebrafish. This work presented a chemical tool for imaging ONOO - in vitro and in vivo.