A comparison of hemolytic and sonochemical activity of ultrasonic cavitation in a rotating tube.

Biological effects of in vitro ultrasonic exposure may result from mechanical and from sonochemical mechanisms related to ultrasonic cavitation. Mechanical cell lysis by 1.61 MHz ultrasonic cavitation was assessed in a rotating tube exposure system by hemolysis measurements. Free radical generation was assessed by the terephthalic acid dosimeter, calibrated by gamma-ray dosage. Sonochemical production was assessed by measuring residual hydrogen peroxide using the sensitive isoluminol method. Exposure conditions were similar for all tests, except longer durations were needed for the free radical and hydrogen peroxide tests. The sonochemical mechanisms were relatively more important for increasing intensity, and increasing temperature. Increasing rotation speed or bubbling with argon before exposure enhanced all cavitation activity. Stopping the rotation reduced all cavitation activity. Burst-mode ultrasound (10.5 microseconds bursts, 1:1 or 1:3 duty cycle) reduced cavitation activity, but gave relatively greater sonochemical activity under some conditions. These results indicate that the mechanical and sonochemical mechanisms can be separately favored to some extent by varying exposure conditions. The observed trends should be helpful for selecting exposure conditions favorable for studying bioeffects of the sonochemical mechanism.