Fig. 1

Ultrasounds setup. For VLIUS exposure, a line of ultrasonic signal was generated by a piezoelectric unfocussed transducer immersed at the bottom of a tank filled with degassed water, powered to a signal generator (Agilent 33220A) and a signal amplifier (Amplifier Research 25A250). A sinusoidal signal at the frequency of 1 MHz was generated and measured by a needle hydrophone (S.N. 2090, Precision Acoustics) of 0.5 mm diameter with a sensitivity of 483 mV/MPa at 1 MHz, connected to an oscilloscope (Tektronix TDS 3052B). Continuous ultrasound exposures in terms of ‘spatial peak temporal average intensity’ (Ispta) equal to 40, 80, 120 and 150 mW/cm² were administered for 15 min on a petri dish (60 mm), submerged up to half of its thickness and aligned coaxially with the transducer, at a fixed distance (Source-dish Surface Distance (SSD) from the transducer