Microchimica Acta | 2019
Fluorometric determination of antioxidant capacity in human plasma by using upconversion nanoparticles and an inner filter effect mechanism
Abstract
AbstractThe balance between free oxygen radicals and antioxidant defense systems is usually assessed by an antioxidant capacity assay. A rapid and sensitive antioxidant capacity assay is described here. It is making use of NaYF4:Yb/Er@NaYF4 core-shell upconversion nanoparticles (UCNPs) and potassium permanganate (KMnO4). In this strategy, added KMnO4 reduces the green (540\xa0nm) emission of the UCNPs (under 980\xa0nm photoexcitation) due to an inner filter effect. The antioxidants cysteine, ascorbic acid and glutathione (GSH) reduce the intense purple color of KMnO4 because it is reduced to Mn(II) ion. Hence, the green upconversion fluorescence is restored after the addition of antioxidants. Figures of merit for this assay (for the case of GSH) include a detection limit of 3.3\xa0μM, a detection range that extends from 10\xa0μM to 2.5\xa0mM, and an assay time of a few seconds. The assay was applied to the evaluation of antioxidant capacity in human plasma samples spiked with GSH and gave satisfactory repeatability and specificity.\n Graphical abstractSchematic presentation of a fluorometric assay based on inner filter effect (IFE) between upconversion nanoparticles (UCNPs) and potassium permanganate (KMnO4) for the determination of antioxidant capacity in human plasma.