Ferroelectric BaTiO3 nanoparticles as peroxidase mimics for colorimetric detection of glutathione S-transferase at physiological pH

The long-standing challenges in peroxidase-mimicking nanozymes catalysis lie in their generally lower catalytic activity in comparison to natural enzymes, as well as only exhibiting specific activities within acidic environments. Herein, BaTiO3 nanoparticles (BTO NPs) operated optimally at a physiological pH and exhibited excellent peroxidase-like activity with the catalytic constant (Kcat) up to 1.99×104 s⁻1 and 9.41×103 s⁻1 for 3,3′,5,5′-tetramethylbenzidine (TMB) and H2O2 substrate, respectively, which is fourfold and twofold that of horseradish peroxidase (4.00×103 s⁻1 and 3.48×103 s⁻1). Mechanism studies suggested that BTO NPs generated internal electric fields due to spontaneous polarization, which drove free carrier separation in different directions. The free carriers led to redox reactions with H2O2 and dissolved oxygen, which produced a variety of reactive oxygen species (ROS), such as•OH, 1O2 and O2•⁻, thus effectively oxidizing the chromogenic substrates. Furthermore, due to its strong reducing property, glutathione (GSH) can inhibit the oxidation of TMB. Conversely, glutathione S-transferase (GST) reduces the inhibition of GSH by facilitating the reaction between GSH and 1-chloro-2,4-dinitrobenzene. Ultimately, a colorimetric method was established for the detection of GST at physiological pH, with a linear range of 0.025 − 5.0 U·L⁻1. This work demonstrated the great promise of screening novel peroxidase mimics with super activities from ferroelectric materials. •BTO NPs show higher peroxidase-like activity than that of HRP at physiological pH.•The mechanism of its catalytic process base on ferroelectric effect is explained.•A colorimetric method is established to detect glutathione S-transferase.