Ultrasonic control of neurite outgrowth direction

This study investigated a method to control neurite outgrowth direction using ultrasound vibration. An ultrasound cell culture dish comprising a glass-bottom culture surface and a glass disc with an ultrasound transducer was fabricated, and undifferentiated neuron-like PC12 cells were grown on the dish as an adherent culture. The 78 kHz resonant concentric flexural vibration mode of the dish was used to quantitatively evaluate the neurite outgrowth direction and length. Time-lapse imaging of cells was performed for 72 h under ultrasound excitation. Unsonicated neurites grew in random directions, whereas neurite outgrowth was circumferentially oriented during ultrasonication in a power-dependent manner. The neurite orientation correlated with the spatial gradient of the ultrasound vibration, implying that neurites tend to grow in directions along which the vibrational amplitude does not change. Ultrasonication with 30 V_pp for 72 h increased the neurite length by 99.7% compared with that observed in unsonicated cells.