Facile fluorescent sensor for rapid and selective detection of phytic acid in food based on phosphatase-like activity of Zr(IV)-Glu complex

Artificial enzymes have attracted much attention in food analysis because of their simple preparation, low cost, and strong stability. However, the most used artificial enzymes are based on oxidoreductases such as oxidase, peroxidase, catalase, and laccase. There are few reports on hydrolases like phosphatase for food analysis. Herein, a novel green zirconium-glutamic acid (Zr(IV)-Glu) complex was prepared using Zr ions and glutamic acid. The Zr(IV)-Glu complex was first found to possess excellent phosphatase-like activity, which was used to establish a fluorescent sensor for detecting phytic acid (PA). The Zr(IV)-Glu complex can catalyze the hydrolysis of 4-methylumbellione phosphate disodium salt (4-MUP) to produce blue fluorescent products with fluorescence emission peaks at 448 nm. PA with six phosphate groups can attach on the surface of Zr(IV)-Glu to form Zr-O-P bond and inhibit the catalytic activity of Zr(IV)-Glu, leading to the decrease of fluorescence in the system. The change of fluorescent intensity at 448 nm was positively correlated with the PA content, so that a fluorescent sensor using the phosphatase-like activity of Zr(IV)-Glu was proposed to detect PA. The established sensor has high sensitivity, low detection limit (LOD) of PA to 58 μg·L-1, strong anti-interference ability, and excellent selectivity. This work can provide a new method for PA detection in food and further expand the application of phosphatase mimics.