Ratiometric fluorescence monitoring of cerebral Cu2+ based on coumarin-labeled DNA coupled with the Cu2+-induced oxidation of o-phenylenediamine.

A novel and facile ratiometric fluorescence method for evaluating Cu2+ has been developed based on coumarin-labeled single-stranded DNA (C-ssDNA) coupled with the Cu2+-induced oxidation of o-phenylenediamine (OPD). By combining the microdialysis technique, the ratiometric fluorescence method has also been successfully exploited to monitor the cerebral Cu2+ in the rat brain, promising new opportunities for studying the cerebral Cu2+-associated physiological and pathological events.

Selective and Sensitive Monitoring of Cerebral Antioxidants Based on the Dye-Labeled DNA/Polydopamine Conjugates.

A simple and novel method for evaluating antioxidants in complex biological fluids has been developed based on the interaction of dye-labeled single-strand DNA (ssDNA) and polydopamine (PDA). Due to the interaction between ssDNA and PDA, the fluorescence of dye-labeled ssDNA (e.g., FITC-ssDNA, as donor) can be quenched by PDA (as acceptor) to the fluorescence "off" state through Förster resonance energy transfer (FRET). However, in the presence of various antioxidants, such as glutathione (GSH), ascorbic acid (AA), cysteine (Cys), and homocysteine (Hcys), the spontaneous oxidative polymerization reaction from DA to PDA would be blocked, resulting in the freedom of FITC-ssDNA and leading to the fluorescence "on" state. The sensing system shows great sensitivity for the monitoring of antioxidants in a fluorescent "turn on" format. The new strategy also exhibits great selectivity and is free from the interferences of amino acids, metal ions and the biological species commonly existing in brain systems. Moreover, by combining the microdialysis technique, the present method has been successfully applied to monitor the dynamic changes of the striatum antioxidants in rat cerebrospinal microdialysates during the normal/ischemia/reperfusion process. This work establishes an effective platform for in vivo monitoring antioxidants in cerebral ischemia model, and promises new opportunities for the research of brain chemistry, neuroprotection, physiological, and pathological events.