Endogenous Hydroxyl Research Articles

Boron-enriched rice-like homologous carbon nanoclusters with a 51.5% photoluminescent quantum yield for highly sensitive determination of endogenous hydroxyl radicals in living cells.

Exploring the ultrahigh quantum efficiency of a carbon-based probe via a green and simple technique, and utilisation of its sensing ability for highly bioactive molecule detection is still highly challenging. Herein, we prepared a novel boron-enriched rice-like homologous carbon nanoclusters (BRCNs) with an ultrahigh quantum efficiency of ∼51.5% by introduction of a conjugated structure attached to the CN bond and an electron-withdrawing boron active centre. Unexpectedly, the BRCNs obtained showed a stable dispersion of rice-like carbon nanograins, composed of small carbon dot assembled nanoclusters with an average diameter size of ∼30 nm, and containing boron units of ∼24.68 at%. What's exciting is that the BRCNs obtained exhibited an "on-off-on" three-state emission with the addition of an hydroxyl radical (OH˙) and its antioxidants. Thus, two distinctive fluorescent responses for OH˙ and antioxidants based on the BRCN probe had been developed, and the mechanism has been determined using TEM, XPS, FT-IR, FL, UV-vis spectrophotometry, UPS and fluorescent lifetimes. The OH˙, generated from the Fenton's reagent, preferentially attack the electron-deficient vacancy p orbit of the boron atom in the surface of the BRCNs, which results in the boron atom being easily substituted/attacked by OH˙, and leading to spontaneous aggregation induced quenching (AIQ) due to the existence of a strong intermolecular hydrogen bond between denatured BRCNs. Furthermore, the proposed method was also successfully applied to monitor endogenous OH˙ generation in HeLa cells by confocal imaging, which could be used for elucidating OH˙-induced oxidative damage to biological tissues and proteins.

Dynamic Detection of Endogenous Hydroxyl Radicals at Single-Cell Level with Individual Ag-Au Nanocages.

Hydroxyl radicals (•OH) are a type of short-lived radical which is the most aggressive reactive oxygen species due to its high reactivity to biomolecules. Dynamic measurement of •OH level in living cells is critical for understanding cell physiology and pathology. In this manuscript, we prepare individual Ag-Au@PEG/RGD nanocages for in situ determination of endogenous •OH at single-cell level, whose spectral shift rate correlate to the •OH concentration. The high-selective response to •OH relies on the specific oxidization of the conjugated PEG/RGD outside and the silver etching inside the nanocages that resulted in a significant LSPR signal and scattered color changes. The spectral red-shift rate of LSPR has a linear relationship with the logarithm of •OH concentration in range of 100 pM to 1 μM, suitable for the measurement of endogenous •OH. Thus, the individual nanocages were successfully used to monitor the dynamic intracellular •OH level of single tumor cells under oxidative stress. This strategy has great potential in promoting •OH mediated cell homeostasis and injury research.

A sensitive BODIPY-based fluorescent probe for detecting endogenous hydroxyl radicals in living cells

The hydroxyl radical (˙OH) has been suggested to play very vital roles in many physiological and pathological processes. However, selective detection of ˙OH is highly challenging owing to its extremely high reactivity and short lifetime. Herein, we designed and synthesized a sensitive “turn on” fluorescent probe for detecting endogenous ˙OH based on a BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) platform. The probe had shown good properties including high sensitively, ideal selectively and low cytotoxicity, and was successfully employed to image endogenous hydroxyl radical in living cells.

A new FRET probe for ratiometric fluorescence detecting mitochondria-localized drug activation and imaging endogenous hydroxyl radicals in zebrafish.

A new FRET probe has been prepared for ratiometric fluorescence detection of hydroxyl radicals. It has been successfully used for detecting mitochondria-localized drug activation in living cells and imaging endogenous hydroxyl radicals in zebrafish gastrointestinal (GI) tracts under normal culturing conditions.

A mitochondrion-targeting turn-on fluorescent probe detection of endogenous hydroxyl radicals in living cells and zebrafish

Detection and imaging of hydroxyl radical (•OH) with high sensitivity and selectivity in biological systems is of great importance in evaluating the role of •OH plays in the physiological and pathological processes. Herein, a novel mitochondrion-targeting turn-on fluorescent probe RThy, has been developed to detect •OH in living cells and zebrafish. Probe’s turn on mechanism is based on the cleavage of azo-bond by •OH. In RThy sensing system, possessing two groups: a lipophilic cation as a targeting-group, and an azo group acts not only as a quenching-group for tunable light absorption but also as recognizing-group of •OH. In the absence of •OH, almost non-fluorescence emission at 550 nm was observed. However, after reaction with •OH, bright fluorescence emission at 550 nm gradually increased with the continuous addition of •OH, displaying ˜50 folds fluorescence intensity enhancements and a quite low detection limit of 8 nM. The selectivity test showed RThy exhibits excellent selectivity toward •OH among all the ROS/RNS species tested. Furthermore, the probe has been successfully employed for imaging •OH in living cells and zebrafish, thus demonstrating RThy as a useful tool for studying •OH in practical sample application, and providing powerful theoretical basis and technical support for investigation of the interaction •OH with physiological and pathology.

A yellow-emissive carbon nanodot-based ratiometric fluorescent nanosensor for visualization of exogenous and endogenous hydroxyl radicals in the mitochondria of live cells

A ratiometric fluorescent nanosensor with high sensitivity was developed for visualization of hydroxyl radicals in the mitochondria of live cells.

A ratiometric fluorescent probe for the detection of endogenous hydroxyl radicals in living cells

A new ratiometric fluorescent probe (4) for monitoring hydroxyl radicals (•OH) has been designed and synthesized. The ratiometric sensing of probe 4 toward •OH is realized by the oxidation of the dicyanovinyl group of probe 4 to afford the corresponding epoxide, which can further reaction with •OH to give a coumarin derivative as the final product. The above reaction interrupts the large π-conjugated system of probe 4 and exhibits a remarkable large blue shift of 160 nm in the emission spectra of the sensing system. Probe 4 exhibits high selectivity toward •OH over other reactive oxygen species and reactive nitrogen species. Preliminary study shows that probe 4 can be employed to monitor endogenous •OH in living cells with a ratiometric fluorescent imaging manner.

HKOH‐1: A Highly Sensitive and Selective Fluorescent Probe for Detecting Endogenous Hydroxyl Radicals in Living Cells

AbstractThe hydroxyl radical (.OH), one of the most reactive and deleterious reactive oxygen species (ROS), has been suggested to play an essential role in many physiological and pathological scenarios. However, a reliable and robust method to detect endogenous .OH is currently lacking owing to its extremely high reactivity and short lifetime. Herein we report a fluorescent probe HKOH‐1 with superior in vitro selectivity and sensitivity towards .OH. With this probe, we have calibrated and quantified the scavenging capacities of a wide range of reported .OH scavengers. Furthermore, HKOH‐1r, which was designed for better cellular uptake and retention, has performed robustly in detection of endogenous .OH generation by both confocal imaging and flow cytometry. Furthermore, this probe has been applied to monitor .OH generation in HeLa cells in response to UV light irradiation. Therefore, HKOH‐1 could be used for elucidating .OH related biological functions.

HKOH-1: A Highly Sensitive and Selective Fluorescent Probe for Detecting Endogenous Hydroxyl Radicals in Living Cells.

The hydroxyl radical (. OH), one of the most reactive and deleterious reactive oxygen species (ROS), has been suggested to play an essential role in many physiological and pathological scenarios. However, a reliable and robust method to detect endogenous . OH is currently lacking owing to its extremely high reactivity and short lifetime. Herein we report a fluorescent probe HKOH-1 with superior in vitro selectivity and sensitivity towards . OH. With this probe, we have calibrated and quantified the scavenging capacities of a wide range of reported . OH scavengers. Furthermore, HKOH-1r, which was designed for better cellular uptake and retention, has performed robustly in detection of endogenous . OH generation by both confocal imaging and flow cytometry. Furthermore, this probe has been applied to monitor . OH generation in HeLa cells in response to UV light irradiation. Therefore, HKOH-1 could be used for elucidating . OH related biological functions.

Sensitive determination of endogenous hydroxyl radical in live cell by a BODIPY based fluorescent probe

The sensitive and selective fluorescence probe for hydroxyl radical analysis is of significance because hydroxyl radical plays key roles in many physiological and pathological processes. In this work, a novel organic fluorescence molecular probe OHP for hydroxyl radical is synthesized by a two-step route. The probe employs 4-bora-3a,4a-diaza-s-indacene (difluoroboron dipyrromethene, BODIPY) as the fluorophore and possesses relatively high fluorescence quantum yields (77.14%). Hydroxyl radical can rapidly react with the probe and quench the fluorescence in a good linear relationship (R2=0.9967). The limit of detection is determined to be as low as 11nM. In addition, it has been demonstrated that the probe has a good stability against pH and light illumination, low cytotoxicity and high biocompatibility. Cell culture experimental results show that the probe OHP is sensitive and selective for imaging and tracking endogenous hydroxyl radical in live cells.

50 - HKOH-1: A Highly Sensitive and Selective Fluorescent Probe for Detecting Endogenous Hydroxyl Radical in Living Cells

Hydroxyl radical (●OH), one of the most reactive and harmful reactive oxygen species (ROS), has been suggested to play an essential role in a lot of physiological and pathological scenarios. Development of fluorescent probes for •OH is highly challenging due to its extremely high reactivity and short lifetime. Here we report a fluorescent probe HKOH-1 with superior in vitro selectivity and sensitivity towards •OH. With this probe, we have calibrated and quantified a wide range of reported •OH scavengers. In addition, HKOH-1 has performed robustly in detection of endogenous •OH generation in multiple cellular models under the settings of both confocal imaging and flow cytometry. Furthermore, this probe has been applied to monitor •OH generation in several types of cells in response to UV light irradiation. Therefore, HKOH-1 could serve as a promising tool for elucidating the •OH-related biological functions.

A fast-responsive turn on fluorescent probe for detecting endogenous hydroxyl radicals based on a hybrid carbazole-cyanine platform

A novel turn on fluorescent probe based on a hybrid carbazole-cyanine platform was designed and synthesized for detecting hydroxyl radicals. The probe had exhibited ideal properties including fast response (0.5min), good selectivity, and low cytotoxicity. Almost 60-fold fluorescence enhancement was obtained in the presence of OH in solution. The novel fluorescent probe could be employed to image endogenous hydroxyl radicals in living cells.

Turn‐On Luminescent Probes for the Real‐Time Monitoring of Endogenous Hydroxyl Radicals in Living Cells

AbstractThe utilization of semiconductor quantum dots (QDs) as optical labels for biosensing and biorecognition has made substantial progress. However, the development of a suitable QD‐based luminescent probe that is capable of detecting individual reactive oxygen species (ROS) represents a great challenge, mainly because the fluorescence of QDs is quenched by a wide variety of ROS. To overcome this limitation, a novel QD‐based turn‐on luminescent probe for the specific detection of .OH has been designed, and its application in monitoring the endogenous release of .OH species in living cells is demonstrated. Metal citrate complexes on the surfaces of the QDs can act as electron donors, injecting electrons into the LUMO of the QDs, while .OH can inject holes into the HOMO of the QDs. Accordingly, electron–hole pairs are produced, which could emit strong luminescence by electron–hole recombination. Importantly, this luminescent probe does not respond to other ROS.

Turn-On Luminescent Probes for the Real-Time Monitoring of Endogenous Hydroxyl Radicals in Living Cells.

The utilization of semiconductor quantum dots (QDs) as optical labels for biosensing and biorecognition has made substantial progress. However, the development of a suitable QD-based luminescent probe that is capable of detecting individual reactive oxygen species (ROS) represents a great challenge, mainly because the fluorescence of QDs is quenched by a wide variety of ROS. To overcome this limitation, a novel QD-based turn-on luminescent probe for the specific detection of (.) OH has been designed, and its application in monitoring the endogenous release of (.) OH species in living cells is demonstrated. Metal citrate complexes on the surfaces of the QDs can act as electron donors, injecting electrons into the LUMO of the QDs, while (.) OH can inject holes into the HOMO of the QDs. Accordingly, electron-hole pairs are produced, which could emit strong luminescence by electron-hole recombination. Importantly, this luminescent probe does not respond to other ROS.

A sensitive fluorescent sensor for the detection of endogenous hydroxyl radicals in living cells and bacteria and direct imaging with respect to its ecotoxicity in living zebra fish.

We have synthesized a novel fluorescent probe, , which shown a high potential for imaging of endogenous ˙OH in living cells and various types of bacteria. In addition, it is an excellent sensor for in vivo imaging of ˙OH generated following treatment with TiO2NPs in zebra fish.

Melatonin as a potential tool against oxidative damage and apoptosis in ejaculated human spermatozoa

It is assumed somatic cells can die in the apoptotic, the autophagic, or the necrotic way; however, the mechanisms of sperm death are not clear. Here, ejaculated human spermatozoa were evaluated for apoptosis and reactive oxygen species production in the absence or presence of melatonin, and we concluded that melatonin reverses sperm apoptosis due to its free radical scavenging actions.

A Novel Antioxidant and Antiapoptotic Role of Omeprazole to Block Gastric Ulcer through Scavenging of Hydroxyl Radical

The mechanism of the antiulcer effect of omeprazole was studied placing emphasis on its role to block oxidative damage and apoptosis during ulceration. Dose-response studies on gastroprotection in stress and indomethacin-induced ulcer and inhibition of pylorus ligation-induced acid secretion indicate that omeprazole significantly blocks gastric lesions at lower dose (2.5 mg/kg) without inhibiting acid secretion, suggesting an independent mechanism for its antiulcer effect. Time course studies on gastroprotection and acid reduction also indicate that omeprazole almost completely blocks lesions at 1 h when acid inhibition is partial. The severity of lesions correlates well with the increased level of endogenous hydroxyl radical (*OH), which when scavenged by dimethyl sulfoxide causes around 90% reduction of the lesions, indicating that *OH plays a major role in gastric damage. Omeprazole blocks stress-induced increased generation of *OH and associated lipid peroxidation and protein oxidation, indicating that its antioxidant role plays a major part in preventing oxidative damage. Omeprazole also prevents stress-induced DNA fragmentation, suggesting its antiapoptotic role to block cell death during ulceration. The oxidative damage of DNA by *OH generated in vitro is also protected by omeprazole or its analogue, lansoprazole. Lansoprazole when incubated in a *OH-generating system scavenges *OH to produce four oxidation products of which the major one in mass spectroscopy shows a molecular ion peak at m/z 385, which is 16 mass units higher than that of lansoprazole (m/z 369). The product shows no additional aromatic proton signal for aromatic hydroxylation in (1)H NMR. The product absorbing at 278 nm shows no alkaline shift for phenols, thereby excluding the formation of hydroxylansoprazole. The product is assigned to lansoprazole sulfone formed by the addition of one oxygen atom at the sulfur center following attack by the *OH. Thus, omeprazole plays a significant role in gastroprotection by acting as a potent antioxidant and antiapoptotic molecule.

Gastroprotective effect of Neem ( Azadirachta indica) bark extract: Possible involvement of H +-K +-ATPase inhibition and scavenging of hydroxyl radical

The antisecretory and antiulcer effects of aqueous extract of Neem ( Azadirachta indica) bark have been studied along with its mechanism of action, standardisation and safety evaluation. The extract can dose dependently inhibit pylorus-ligation and drug (mercaptomethylimidazole)-induced acid secretion with ED 50 value of 2.7 and 2 mg Kg −1 b.w. respectively. It is highly potent in dose-dependently blocking gastric ulcer induced by restraint-cold stress and indomethacin with ED 50 value of 1.5 and 1.25 mg Kg −1 b.w. respectively. When compared, bark extract is equipotent to ranitidine but more potent than omeprazole in inhibiting pylorus-ligation induced acid secretion. In a stress ulcer model, it is more effective than ranitidine but almost equipotent to omeprazole. Bark extract inhibits H +-K +-ATPase activity in vitro in a concentration dependent manner similar to omeprazole. It offers gastroprotection against stress ulcer by significantly preventing adhered mucus and endogenous glutathione depletion. It prevents oxidative damage of the gastric mucosa by significantly blocking lipid peroxidation and by scavenging the endogenous hydroxyl radical ( OH)-the major causative factor for ulcer. The OH-mediated oxidative damage of human gastric mucosal DNA is also protected by the extract in vitro. Bark extract is more effective than melatonin, vitamin E, desferrioxamine and α-phenyl N-tert butylnitrone, the known antioxidants having antiulcer effect. Standardisation of the bioactive extract by high pressure liquid chromatography indicates that peak 1 of the chromatogram coincides with the major bioactive compound, a phenolic glycoside, isolated from the extract. The pharmacological effects of the bark extract are attributed to a phenolic glycoside which is apparently homogeneous by HPLC and which represents 10% of the raw bark extract. A single dose of 1g of raw extract per kg b.w. (mice) given in one day and application of 0.6g raw extract per kg b.w. per day by oral route over 15 days to a cumulative dose of 9g per kg was well tolerated and was below the LD 50. It is also well tolerated by rats with no significant adverse effect. It is concluded that Neem bark extract has therapeutic potential for the control of gastric hyperacidity and ulcer.

Cyclic 3-Hydroxymelatonin: A Melatonin Metabolite Generated as a Result of Hydroxyl Radical Scavenging

The pineal secretory product, melatonin, is a potent, endogenous hydroxyl radical (HO·) scavenger. When melatonin was incubated in different in vitro cell-free HO·-generating systems, a novel melatonin adduct was formed. The molecular weight of this new compound is 248. Its structure was found to be cyclic 3-hydroxymelatonin (3-OHM). A proposed reaction pathway suggests that 3-OHM is the footprint product of the interaction between melatonin with HO·. 3-OHM was also detected in the urine of both rats and humans. This urinary metabolite is identical to the compound generated in the in vitro chemical reaction between HO· and melatonin. This provides direct evidence that melatonin, under physiological conditions, functions as an antioxidant to detoxify the most reactive and cytotoxic endogenous HO·. When exogenous melatonin was administered to young rats, urinary 3-OHM levels increased significantly in the treated rats compared to those in controls. This indicates that even in young animals there is insufficient endogenously produced melatonin to detoxify the basal levels of the toxic HO·. The accumulated damage induced by the escaped HO· that results when the HO· avoids detoxification over the course of a life time may directly or indirectly accelerate aging and aging-related diseases.

ROLE OF ENDOTHELIAL-DERIVED REACTIVE OXYGEN SPECIES AND NITRIC OXIDE IN NOREPINEPHRINE-INDUCED RAT AORTIC RING CONTRACTIONS

In the present investigation involvement of endothelial-derived reactive oxygen species (ROS) and their interaction with nitric oxide (NO), during norepinephrine (NE)-induced contraction of rat aortic rings was studied. NE (1×10−10mto 1×10−5m) caused concentration-dependent contractio n of the endothelium intact aortic rings. In the presence of hydroxyl radical scavengers, histidine (1×10−3m), mannitol (3×10−3m), dimethyl sulfoxide (50×10−3m) or thiourea (1×10−3m), superoxide dismutase (superoxide radical scavenger, SOD 10 or 100 U ml−1) or catalase (hydrogen peroxide inactivator 3, 10, or 100 U ml−1) the concentration–response curve of NE was shifted towards the right. Interestingly, inNG-nitro-l-arginine methyl ester (l-NAME) (1×10−5m, a NO synthase inhibitor) pretreated rings, NE-induced contractions were not inhibited by SOD or extracellular hydroxyl radical scavengers (mannitol and histidine). However, in these rings NE-induced contractions were found to be attenuated by endogenous hydroxyl radical scavengers (thiourea and DMSO) or catalase. In the endothelium denuded rings no significant effect of these scavengers on NE-induced contractions was observed. These results thus indicate the involvement of endothelium-derived hydrogen peroxide, superoxide and hydroxyl radicals in the NE-induced contractions. In addition, endothelial NO interacts with the ROS generated during rat aortic ring contractions.