TiO₂-Templated BaTiO₃ Nanorod as a Piezocatalyst for Generating Wireless Cellular Stress

Although the piezoelectric property of a BaTiO3 nanoparticle is routinely used in energy harvesting application, it can also be exploited for wireless cell stimulation and cell therapy. However, such biomedical application is rare due to limited availability of colloidal BaTiO3 nanoparticles of <100 nm hydrodynamic size with good piezocatalytic property and efficient biolabeling performance. Here, we report a colloidal form of a piezocatalytic BaTiO3-based nanorod of <100 nm hydrodynamic size that can offer wireless cell stimulation. The nanorod is prepared using a TiO2 nanorod as the template, and the resultant TiO2–BaTiO3-based composite nanorod is coated with a hydrophilic polymer shell. These nanorods can label cells and, under the ultrasound exposure, produce reactive oxygen species inside cells via piezocatalysis, leading to cell death. These nanorods can be used for wireless modulation of intracellular processes.