Manganese Phthalocyanine-Based Magnetic Core–Shell Composites with Peroxidase Mimetic Activity for Colorimetric Detection of Ascorbic Acid and Glutathione

Ascorbic acid (AA) and glutathione (GSH) play a pivotal role in health assessment, drug development, and quality control of nutritional supplements. The development of a new and efficient method for their detection is highly desired. In this work, we fabricated magnetic core-shell nanocomposites (Fe₃O₄@MnPc-NDs) by a one-pot hydrothermal method with citric acid and manganese tetraamino phthalocyanine (MnTAPc) as precursors. Fe₃O₄@MnPc-NDs exhibited enhanced peroxidase activity compared to bare Fe₃O₄ nanoparticles, enabling catalytic oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue ox-TMB in the presence of H₂O₂. Leveraging the antioxidant properties of AA/GSH to reduce ox-TMB, a colorimetric assay achieved a low detection limit of 0.161 μM for AA and 0.188 μM for GSH with broad linear ranges. Moreover, this method displayed high specificity against 12 interfering substances and excellent recyclability (>90% activity after five cycles). Finally, the Fe₃O₄@MnPc-NDs could act as an efficient colorimetric sensor for accurately detecting AA in genuine VC tablets and GSH in whitening serums with high accuracy. Therefore, Fe₃O₄@MnPc-NDs exhibited great potential in bioassay applications, benefiting from their outstanding sensitivity and high recycling rate.