To evaluate in vitro the feasibility of therapeutic high-intensity-focused ultrasound (HIFU) combined with microbubbles and titanium dioxide (TiO2).
Oral squamous cell carcinoma cells (HSC-2) were sonicated using a HIFU transducer with a resonant frequency of 3.5 MHz, 30 mm in diameter, and focal length of 50 mm. The ultrasound intensity was 210 W/cm(2), and two pulses (0.5 s each) were sonicated for each cell sample (9 x 10(4) cells per well). Immediately after HIFU, the viable cells were measured by an automated cell counter. The survival rate was measured in the presence of microbubbles (Sonazoid) and peroxo titania-silica (R-P-TS) or anatase titania-silica (R-A-TS) TiO2.
Cell viability immediately following sonication in the presence of TiO2 (R-A-TS) and TiO2 (R-P-TS) was 65.5 +/- A 0.7 and 59.4 +/- A 3.3 %, respectively. A marked decrease in cell viability was seen when microbubbles were added to the above cell conditions. Specifically, cell viability decreased to 14.0 +/- A 0.1 and 4.4 +/- A 0.9 % when microbubbles were added to samples containing TiO2 (R-A-TS) and TiO2 (R-P-TS), respectively.
Immediate in vitro cell killing was observed with short pulsed duration HIFU sonication with a combination of microbubbles and TiO2. This finding suggests that TiO2 could have caused enhanced mechanical cell destruction by microbubbles.