A multichromatic colorimetric detection method for Vibrio parahaemolyticus based on Fe₃O₄-Zn-Mn nanoenzyme and dual substrates

A successful development of a dual-substrate colorimetric system for rapid and multicolorimetric semi-quantification of Vibrio parahaemolyticus (V. parahaemolyticus) has been achieved. The enzymatic activity of Fe3O4-Zn-MnO2-aptamer (Fe3O4-Zn-Mn-Apt) catalysts can induce the oxidation of 3,3 ',5,5 '-tetramethylbenzidine (TMB) to form oxidized TMB (TMB+ with a bluish green color) and ortho-phenylenediamine (OPD) to form oxidized OPD (with yellow color), resulting in a three-color comparison due to the complementary nature of bluish green and yellow. The absorbance value of TMB+ at 652 nm is used for the determination of V. parahaemolyticus. After optimizing the reaction conditions, the developed dual-substrate colorimetric method exhibits high sensitivity for V. parahaemolyticus detection (limit of detection of 1.12 cfu mL(-1)) and a linear range of 0-1 x 10(4) cfu mL(-1) (R-2 = 0.9934). Additionally, as the concentration of V. parahaemolyticus increases, the reaction solution changes from bluish green to green and then to yellow, enabling semi-quantitative detection by visual observation with a visual detection limit of 10 cfu mL(-1). Furthermore, the developed dual-substrate colorimetric method demonstrates excellent selectivity for V. parahaemolyticus detection and satisfactory recovery rates when applied to the determination of V. parahaemolyticus in food samples.