Sonoluminescence as an indicator of cell membrane disruption by acoustic cavitation

Ultrasound (US) has been shown to transiently disrupt cell membranes and, thereby, facilitate the loading of drugs and genes into viable cells. Because these effects are believed to be mediated by cavitation, we hypothesized that measured levels of cavitation-induced sonoluminescence should correlate with levels of US bioeffects. We, therefore, quantified the number of calcein molecules delivered and the loss of viability in prostate cancer cells exposed to 24-kHz US over a range of different pulse lengths (1 to 100 ms), total exposure times (0.1 to 10 s) and pressures (1.0 to 9.8 atm). Consistent with previous observations, uptake increased and viability decreased with increasing pulse length, total exposure time and pressure. As a new observation, we established correlations between the amount of light produced by sonoluminescence and both molecular uptake and cell viability. These results support a cavitation-based mechanism for these bioeffects and suggest a means to control US effects on cells using sonoluminescence-based feedback.