Abstract
One interesting aspect of antioxidant organic molecules is their use as probes for the detection and quantitation of biologically relevant reactive oxidant species (ROS). In this context, a small library of dihydroterphenyl derivatives has been synthesised and studied as fluorescent chemodosimeters for detecting reactive oxygen species and hypochlorite. The fluorescence quantum yields of these molecules are negligible, while the corresponding aromatized compounds formed upon oxidation show moderate to high native fluorescence, depending on their structures. The fluorescence signal is quickly developed in the presence of trace amounts of the probe and the analytes in acetonitrile media at room temperature, with good analytical figures. ROS detection in aqueous media required incubation at 37 °C in the presence of horseradish peroxidase, and was applied to glucose quantitation by coupling glucose oxidation by O2 to fluorescence detection of H2O2. The mild reaction conditions and sensitive fluorescent response lead us to propose dihydroterphenyls with an embedded anthranilate moiety as chemosensors/chemodosimeters for ROS detection.
Highlights
Reactive oxygen species (ROS) [1] exert important physiological roles, being involved in processes such as cell signaling and immune responses [2,3], but on the other hand, their buildup in cells is linked to the mechanisms leading to a number of pathological conditions including cardiovascular disorders [4,5], cancer [6,7] and neurodegenerative diseases [8,9]
Several characteristics are desirable for a fluorescent dye with sensing properties [22,23,24,25], namely: (a) an adequate hydrophobicity/hydrophilicity balance to ensure both membrane permeability and solubility in biological media; (b) biocompatibility, with no interference with endogenous cellular processes; (c) good analytical features: sensitivity, selectivity and linear range; (d) a high fluorescence emission intensity, preferably only upon reaction with the target analyte; (e) photo-stability; (f) in the case of sensors to be employed for bioimaging, emission in the red or near infrared is an additional useful feature
Due to the need to have the isolated products formed in the analytical reaction in hand for reference purposes, compounds A were dehydrogenated in good to excellent yields to the aromatic derivatives B by exposure to 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) at room temperature
Summary
Reactive oxygen species (ROS) [1] exert important physiological roles, being involved in processes such as cell signaling and immune responses [2,3], but on the other hand, their buildup in cells is linked to the mechanisms leading to a number of pathological conditions including cardiovascular disorders [4,5], cancer [6,7] and neurodegenerative diseases [8,9]. Antioxidants 2020, 9, 605 the mitochondrial electron transport chain, and high levels of mitochondrial hydrogen peroxide are a contributing factor in the pathogenesis of Parkinson’s [10] and Alzheimer’s [11] diseases. Other biological hydroperoxides such as prostaglandin G2 [12] or protein hydroperoxides [13] are important agents of oxidative stress. Another significant ROS is hypochlorite, which is synthesized in living organisms from hydrogen peroxide and chloride ions, mainly inside leukocytes, in a reaction catalyzed by the enzyme myeloperoxidase (MPO) [14]. Several characteristics are desirable for a fluorescent dye with sensing properties [22,23,24,25], namely: (a) an adequate hydrophobicity/hydrophilicity balance to ensure both membrane permeability and solubility in biological media; (b) biocompatibility, with no interference with endogenous cellular processes; (c) good analytical features: sensitivity, selectivity and linear range; (d) a high fluorescence emission intensity, preferably only upon reaction with the target analyte (i.e., turn-on behaviour); (e) photo-stability; (f) in the case of sensors to be employed for bioimaging, emission in the red or near infrared is an additional useful feature
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