Experimental study of the effects of Optison concentration on sonoporation in vitro

Lethal sonoporation and reparable sonoporation were observed in Jurkat lymphocytes in suspension with the addition of varying amounts of Optison, a commercially available bubble-based contrast agent. For given ultrasound (US) exposure conditions (spatial peak-pressure amplitude of 0.2 MPa, duty cycle 10% and 2-MHz frequency), sonoporation was directly related to the bubble-to-cell ratio (in a range from 0 to 230). It was found that the nearest bubble-cell spacing was also related to the occurrence frequency of bioeffects. A constant bubble-to-cell ratio often provided very different results for two different initial cell concentrations (200,000 cells/mL and 600,000 cells/mL), with the higher cell concentration generally exhibiting higher levels of sonoporation. In contrast, a constant bubble-to-cell spacing provided similar results between the two initial cell concentrations. The frequency of reparable and lethal sonoporation was seen to decay as the inverse-cube power of the nearest bubble-cell spacing. Significant reparable sonoporation was observed at a bubble-cell spacing that was 10 microm larger than the minimum spacing at which significant lethal sonoporation was observed. Preliminary analysis also suggests the possibility of a step-wise increase in lethal sonoporation as spacing decreases; further experiment is needed.