Colorimetric sensor array for accurate detection and identification of antioxidants based on metal ions as sensor receptors

There is an ongoing need to develop high-performance sensing strategy for detecting and discriminating antioxidants, primarily because of their role in medical diagnosis and food. In this regard, visual sensor arrays have been a subject of intensive research for such applications. To this end, we propose a colorimetric sensor array for accurate detection and identification of antioxidants, which is based on the reactions between 3,3',5,5'-tetramethylbenzidine (TMB) and metal ions as sensing receptors and the interactions between antioxidants and oxidized TMB (oxTMB). Different target antioxidants displayed diverse reduction abilities toward the oxTMB, creating distinct colorimetric response patterns. The combination of colorimetric response variation at color and absorbance at 652 nm enables the sensor array to provide a unique fingerprint pattern to each antioxidant. Linear discriminant analysis (LDA) and centroid diagrams show that the sensor array can well detect and discriminate the eight tested antioxidants, including lipoic acid (LIA), cysteine (Cys), tannin (TA), ascorbic acid (AA), glutathione (GSH), Uric Acid (UA), glycine (Gly), and dopamine (DA), with a high sensitivity in the range of nanomolar concentrations.