Experimental study on cell self-sealing during sonoporation.

Reparable sonoporation of human breast cancer cells was achieved during exposure to moderate ultrasound (spatial peak acoustic pressure, p(sp)=0.25 MPa, 1 MHz tone-bursts, 20 cycles per tone-burst at pulse repetition frequency of 10 kHz) up to 40 s assisted by the presence of encapsulated microbubbles (EMBs). It was demonstrated that shear stress generated by oscillating EMBs at the cell membranes introduced small transient pores in cell membranes by which cells were able to uptake some extracellular fluid and meanwhile triggered the repairing process through self-sealing during sonoporation. It was also indicated by post-sonoporation analysis using the fluorescent microscopy, scanning electron microscopy, and the Bradford assay which determined the protein content in cell supernatant that the self-sealing might be established by lysosomal-associated membrane protein, LAMP-1, fusing with the plasma membrane under the stressful condition in sonoporation.