A novel iodine-mediated FRET sensor for the assessment of total antioxidant capacity

Accurate quantification of total antioxidant capacity (TAC) is crucial for evaluating the overall antioxidant activity in biological systems and food products. This is of growing importance in diverse applications such as health risk assessment and nutritional recommendations. Here, we introduce a novel Förster resonance energy transfer (FRET)-based sensor for the determination of TAC. The sensor utilizes an iodine-mediated FRET mechanism, employing BODIPY as the donor and Nile Red as the acceptor, both encapsulated within polystyrene (PS) microspheres. In the presence of iodine, its lipophilicity facilitates adsorption into the PS microspheres, resulting in fluorescence quenching due to the heavy-atom effect. This quenching results in an increased distance between the unquenched donors and acceptors, thereby decreasing FRET efficiency. Conversely, the presence of antioxidants reduces iodine concentration, which increases FRET efficiency. This dynamic allows for the development of a ratiometric fluorescence method for TAC determination. Critically, the sensor demonstrates exceptional photostability and resilience to variations in pH and ionic strength, contributing to its analytical robustness. The proposed method exhibits a linear response to ascorbic acid concentrations ranging from 0 to 50 μM, exhibiting good sensitivity (LOD = 2.5 μM) and selectivity. Additionally, the method has been successfully applied to evaluate TAC in ascorbic acid chewable tablets and lemon juice, demonstrating its potential as a robust and efficient tool for TAC determination.