Nano-piezoelectric BaTiO activate water to overcome pH limitations: A novel oxidase-mimicking strategy for cystathionine-γ-lyase colorimetric biosensing.

Cystathionine-γ-lyase (CSE) is a pivotal bio-enzyme that catalyzes the cleavage of cystathionine, whose expression has been linked to a myriad of severe illnesses and tumorigenic processes. The development of reliable and sensitive detection plays an important role in better understanding the physiology and pathology of CSE. Herein, we introduce a facile colorimetric assay for CSE detection in physiological media, utilizing tetragonal barium titanate (T-BTO) nanoparticles (NPs) as an innovative oxidase-like (OXD) nanozyme. Interestingly, T-BTO NPs demonstrate exceptional piezoelectric responsiveness upon ultrasound (US) stimulation, allowing their mimic oxidase activity to be finely tuned through the piezoelectric effect. Our investigation into the reaction mechanism revealed that localized polarization and swift charge carrier separation near the interface of T-BTO NPs markedly enhance catalytic efficiency with a high catalytic rate constant (K = 1.25 × 10 s) for 3,3',5,5'-tetramethylbenzidine (TMB)-oxidation at neutral pH, attributed to the efficient activation of HO molecules into reactive oxygen species (ROS). Leveraging the significant inhibitory effect exerted by HS, a sensitive, straightforward, and cost-effective assay for CSE in physiological environments was thus established. A linear response was obtained for CSE detection from 0.10 to 200 U/L, with a limit of detection (LOD) of 0.099 U/L. This study represents a synergistic integration of piezocatalytic and enzymatic functionalities, offering an approach for the rational design of molecular detection methods targeting crucial biological enzymes.