EDTA–Fe2+ Complex-Functionalized Fe3O4 Nanozyme as Tyrosine Hydroxylase Mimics for the Production of l-DOPA

l-3,4-Dihydroxyphenylalanine (l-DOPA) is widely used in the treatment of Parkinson's disease. Fe3O4 magnetic nanoparticles decorated with ethylenediaminetetraacetic acid (EDTA)–Fe2+ complexes were developed as nanozymes for the biomimetic synthesis of l-DOPA by mimicking tyrosine hydroxylase. The nanozyme was synthesized by anchoring Fe2+ ions onto EDTA-grafted Fe3O4 magnetic nanoparticles. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier-transform infrared, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller, and vibrating-sample magnetometer characterized the nanozyme-possessed nanoscale features, high specific surface area, and good superparamagnetic properties. The nanozyme has a coordination structure comprising an EDTA–Fe2+ complex that resembles the catalytic site of tyrosine hydroxylase. The nanozyme exhibited high catalytic performance for the conversion of tyrosine to l-DOPA, with properties similar to those of tyrosine hydroxylase (Km = 8.7 mM). The yield and titer of l-DOPA were 28% and 1.7 mM, respectively. The nanozyme showed excellent reusability over five successive cycles. The data showed that hydroxyl radicals and singlet oxygen are the primary active species and the catalytic mechanism of the nanozyme is similar to that of tyrosine hydroxylase. The magnetically separable and recyclable nanozyme has potential applications in the low-cost and high-efficiency production of l-DOPA.