A Novel Four-Channel Sensor Array with Dual Enzymes and Dual Modes for Evaluating Total Antioxidant Capacity in Foods

Antioxidants are essential for preventing cellular and organ damage caused by reactive oxygen species (ROS). Consequently, the total antioxidant capacity (TAC) of food products was a critical criterion for assessing their quality. This study presented a novel dual-mode, four-channel sensor array platform for the highly sensitive detection of TAC, which employed the exceptional dual enzyme activity of mesoporous silica nanoparticles loaded with iron and nitrogen codoped carbon quantum dots (Fe,N-CQDs@MSNs) through pattern recognition methods. The dual-enzyme-like nanocatalysts exhibited: (1) Peroxidase-like activity in which Fe,N-CQDs@MSNs facilitated the activation of H₂O₂, yielding hydroxyl radicals (^•OH); and (2) photoresponsive oxidative activity, where Fe,N-CQDs@MSNs generated ^•OH, superoxide anions (^•O₂^-), and singlet oxygen (¹O₂) under UV light at 365 nm. These ROS oxidized 3,3',5,5'-tetramethylbenzidine (TMB) from colorless to blue, accompanied by fluorescence quenching in Fe,N-CQDs@MSNs. Upon adding four antioxidants ascorbic acid (AA), glutathione (GSH), cysteine (Cys), and dopamine (DA), the reactive intermediates were eliminated to varying degrees, leading to distinct UV and fluorescence responses as specific "fingerprints" for the sensor array. Multivariate statistical approaches, including principal component analysis (PCA) and hierarchical clustering analysis (HCA), enabled the distinct classification of the four antioxidants, achieving a detection limit of 1 μM. Additionally, the sensor array enabled the identification of varying concentrations of individual antioxidants as well as mixtures in different proportions. Finally, the proposed method was effectively employed for the quantitative determination of TAC in diverse food samples, yielding satisfactory results and demonstrating its potential for TAC detection in food products.