Combined effect of ultrasound/SonoVue microbubble on CD4+CD25+ regulatory T cells viability and optimized parameters for its transfection

The purpose of this study was to investigate the combined effect of ultrasound and SonoVue microbubble on CD4+CD25+ regulatory T cells (Tregs) viability and to explore the appropriate parameters for Tregs transfection. Tregs were separated from peripheral venous blood of patients with hepatocellular carcinoma and seeded in 96-well plates. The optimal ultrasound exposure time and optimal SonoVue microbubble concentration for Tregs were measured by mechanical index (MI) of 1.2 or 1.4, exposure time of 0, 30, 60, 90, 120, 150, 180 s, and 0, 10, 20, 30, 40, 50 μL/100 μL microbubble per well, respectively. In addition, the combined effect of ultrasound and microbubble on Tregs viability was evaluated according to the following parameters: MI 1.2/1.4 + exposure time of 120, 150, 180 s + 0, 10, 20, 30, 40, 50 μL/100 μL microbubble per well. Tregs viability investigations were performed in order to explore the optimal transfection condition. The efficiency of plasmid transfer was determined by detection of luciferase activity on the microscopic examinations. The proliferation of Tregs could be promoted by ultrasound exposures, while being decreased with the increasing concentration of microbubbles. Under the current experimental conditions, the optimal ultrasound parameters were MI = 1.4 and exposure time = 150/180 s. The optimal microbubble concentration was 10 μL/100 μL. Compared with treatment with ultrasound or microbubbles alone, the transfection efficiency of Tregs improved 50% by combining ultrasound and microbubble. The results indicate that both ultrasound and microbubble could affect the Tregs proliferation and the optimal Treg transfection rate was obtained by treating with 10% microbubbles and ultrasound exposure for 150/180 s under ultrasound MI of 1.4.