Acoustic Propulsion of Nanorod Motors Inside Living Cells

The ultrasonic propulsion of rod-shaped nanomotors inside living HeLa cells is demonstrated. These nanomotors (gold rods about 300nm in diameter and about 3m long) attach strongly to the external surface of the cells, and are readily internalized by incubation with the cells for periods longer than 24h. Once inside the cells, the nanorod motors can be activated by resonant ultrasound operating at 4MHz, and show axial propulsion as well as spinning. The intracellular propulsion does not involve chemical fuels or high-power ultrasound and the HeLa cells remain viable. Ultrasonic propulsion of nanomotors may thus provide a new tool for probing the response of living cells to internal mechanical excitation, for controllably manipulating intracellular organelles, and for biomedical applications.