Determination of the activity of hydrogen peroxide scavenging by using blue-emitting glucose oxidase-stabilized gold nanoclusters as fluorescent nanoprobes and a Fenton reaction that induces fluorescence quenching

The authors describe a rapid and sensitive method for the determination of the activity of scavenging hydrogen peroxide in which glucose oxidase-stabilized gold nanoclusters (AuNCs) were employed as a fluorescent nanoprobe. The AuNCs are synthesized by a biomineralization process and display an intense blue fluorescence peaking at 450 nm and a quantum yield of 1.1% under 360-nm excitation. The Fenton reaction induces quenching of fluorescence, and this effect can be used to determine H2O2 in the 0.5 to 10 mu molai...L-1 concentration range. The substances displaying H2O2 scavenging activity prevent quenching and thus restore fluorescence. The intensity of restored fluorescence is directly related to the H2O2 scavenging activity of the antioxidant. The method was applied to the determination of the H2O2 scavenging activity of the model antioxidants ascorbic acid and tartaric acid which gave IC50 values of 7.4 and 19.1 mu molai...L-1, respectively.