Ultrasound-Directed Switching between Autophagy and Apoptosis via Barium Titanate Nanorod-Based Intracellular Sono-Piezocatalysis

Piezoelectric barium titanate nanoparticles can convert mechanical energy into electrical/chemical energy and catalyze redox reactions, which can be used for mechanotherapy-based treatment of tumors/neurological diseases/bacterial disinfection via the remote use of ultrasound. However, better piezoelectric properties require larger particle sizes (>100 nm), and better cell targeting requires smaller particle sizes (<100 nm), which restricts their wider biomedical application potential. Here, we report <100 nm sized colloidal barium titanate nanorods with good piezoelectric properties suitable for cell targeting, followed by remotely used ultrasound parameter-directed switching between cellular apoptosis and autophagy. The colloidal and functional nanorod is designed for selective cell labeling, and then ultrasound intensity/time is used to control the extent of intracellular reactive oxygen species via sono-piezocatalysis, which switches between apoptosis and autophagy. The proposed therapeutic approach can be adapted for apoptotic cell death or autophagy-induced cell repair/recycling at a remote place in the body, via focused ultrasound or other mechanical stress.