The reversible surface redox of polymer dots for the assay of total antioxidant capacity in food samples

Abstract

In this paper, polymer dots (Pdots) were synthesized by one-step nanoprecipitation method from cationic conjugated polymer and hyaluronic acid, it was found that the fluorescence of Pdots could be reversibly quenched by NaClO. Mechanism study indicated that the reversible quenching was resulted from the reversible surface redox process of Pdots with NaClO and antioxidants. Based on this phenomenon, a reusable determination strategy of total antioxidant capacity (TAC) was developed. Three nonenzymatic antioxidants and two enzymatic antioxidants were selected as model targets to test its detection ability, and the detection linear ranges are 0.1–50 μM for glutathione and ascorbic acid, 0.5–10 μM for N-acetyl-l-cysteine, 1–30 U mL−1 for superoxide dismutase and 1–20 U mL−1 for catalase. Compared with standard assay method of total antioxidant capacity, this Pdots-NaClO system simplified operation process and meanwhile increased sensitivity. Moreover, this strategy has a great potential in the assay of food quality, as it was successfully applied to investigate TAC in fruit and tea samples with satisfactory recoveries ranging from 88.4% to 114.2%, and the relative standard deviation of the obtained TAC value was from 3.2% to 9.9%.