Sonocatalytic injury of cancer cells attached on the surface of a nickel–titanium dioxide alloy plate

• Nickel–titanium dioxide alloy plate was used as sonocatalyst and culture surface.
• Nickel–titanium alloy plate was used as a non-sonocatalytic control.
• Ultrasound irradiation of nickel–titanium dioxide alloy plate generated hydroxyl radical.
• Ultrasound irradiation injured cancer cells on nickel–titanium dioxide alloy plate.
• Ultrasound irradiation of cancer cells on Ni–TiO2 alloy plate led to apoptosis.

The present study demonstrates ultrasound-induced cell injury using a nickel–titanium dioxide (Ni–TiO2) alloy plate as a sonocatalyst and a cell culture surface. Ultrasound irradiation of cell-free Ni–TiO2 alloy plates with 1 MHz ultrasound at 0.5 W/cm2 for 30 s led to an increased generation of hydroxyl (OH) radicals compared to nickel–titanium (Ni–Ti) control alloy plates with and without ultrasound irradiation. When human breast cancer cells (MCF-7 cells) cultured on the Ni–TiO2 alloy plates were irradiated with 1 MHz ultrasound at 0.5 W/cm2 for 30 s and then incubated for 48 h, cell density on the alloy plate was reduced to approximately 50% of the controls on the Ni–Ti alloy plates with and without ultrasound irradiation. These results indicate the injury of MCF-7 cells following sonocatalytic OH radical generation by Ni–TiO2. Further experiments demonstrated cell shrinkage and chromatin condensation after ultrasound irradiation of MCF-7 cells attached on the Ni–TiO2 alloy plates, indicating induction of apoptosis.