Colorimetric Biosensor Based on Fe-HHTP@ZIF-8 for the Detection of Total Antioxidant Capacity in Beverages

Total antioxidant capacity of food is one of the critical parameters to evaluate its efficacy. Establishment of a fast and sensitive analytical method for the detection of total antioxidant capacity of food has great significance. In this paper, a metal-organic framework complex nanozyme (Fe-HHTP@ZIF-8) with peroxidase-like activity was firstly designed and successfully synthesized. Then, the morphology, structure and catalytic activity were characterized in detail. The results showed that Fe-HHTP@ZIF-8 possessed a two-dimensional ultra-thin layer structure while its K_m and V_max values towards H₂O₂ were 0.67 mmol/L and 3.55×10⁻⁸ mol/L·s⁻¹, respectively. Ascorbic acid (AA) as a typical antioxidant, an efficient colorimetric biosensor was constructed based on its inhibitory effect on chromogenic reaction catalyzed by nanozyme. Comprehensive validation showed that the colorimetric biosensor had low limit of detection (1.67 μmol/L), wide linear range (5.0~3000.0 μmol/L) and high accuracy (recovery rate of 98.62%~103.13%). By using this colorimetric method, total antioxidant capacity of different beverages was detected and the obtained results were basically consistent with labeled values. Therefore, this study provided a simple, fast and effective colorimetric method for the evaluation of the total antioxidant capacity of food.