The relationship of scattered subharmonic, 3.3-MHz fundamental and second harmonic signals to damage of monolayer cells by ultrasonically activated Albunex®

Cultured Chinese hamster ovary cells attached to thin Mylar sheets were exposed to 3.3-MHz ultrasound in the presence of Albunex(R) ultrasound contrast agent. The ultrasound beam was directed upward at the exposure chamber with the monolayer on the inside of the upper acoustic window. Cell membrane damage was detected by the firefly enzyme assay for released ATP and the subharmonic, fundamental, and second harmonic scattered signals were recorded. ATP release increased monotonically with increasing pressure amplitude above apparent thresholds of 0.28 MPa for 1-s continuous and 0.56 MPa for 100-s pulsed (10-mu s pulses, 1-ms PRP) exposures with 5% Albunex(R). The subharmonic signal and, to a lesser extent, the second harmonic signal both increased with the cell membrane damage, which suggests that these signals have predictive value for bioeffects. If the monolayer was positioned on the front window of the exposure chamber, cell membrane damage was greatly reduced, which confirms the protective influence of this configuration of monolayers reported in the literature. The effect decreased both at high (50%) or low (0.5%) concentrations of Albunex(R). The strong nonlinear scattering of ultrasound by contrast agent gas bodies appears to provide useful indicators of gas body activity including cavitational bioeffects. (C) 1998 Acoustical Society of America. [S0001-4966(98)06301-2].