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N. G. Lee, A. T. Wang, T. C. Lee, A. A. Fawzi; In vitro Sonoporation of Retinoblastoma Y79 Cells. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2061.
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© ARVO (1962-2015); The Authors (2016-present)
Ultrasound (US) induced sonoporation has potential applications. It has been shown that US in the presence of microbubbles (US/MB) can enhance cell permeability and improve targeted drug delivery. This approach has been implemented in many tumor cells both in vitro and in vivo, but not in retinoblastoma (Rb). The use of transient sonoporation in Rb cells can potentially allow for smaller doses of chemotherapy, with ultrasound directing it to the tumor site. Our aim is to identify the optimum dose of US/MB to induce cell pores in Rb cells.
Rb cell line Y79 grown in media (4x106 ) was sonicated at 1 MHz US for 60 seconds (20% duty cycle) US was investigated for powers ranging from 1 W/cm2 to 10 W/cm2. A subsequent experiment evaluated low power US between 0.3W/cm2 and 1 W/cm2, and was then repeated in the presence of US/MB. In all experiments, cell death was assessed by Trypan blue exclusion (TBE) at 30 minutes, 6 hours, and 24 hours post-US. Treated cells were fixed and studied using scanning electron microscopy (SEM).
In the high power US experiment, we observed a significant increase in the proportion of dead cells on TBE (40%) when US power reached 5 W/cm2. The same trend was seen at 6 hours and 24 hours where the cell viability was only 50% at 5 and 10 W/cm2. Low power US did not cause an appreciable difference in the cell viability between 0.3 and 1 W/cm2; however, when MB/US was done, cell viability decreased by ten orders of magnitude. On SEM, cells treated with US/MB developed pores, which exhibited a dose effect and were larger and more numerous at 1 W/cm2 than at 0.3 W/cm2.
In this experiment, we identified the lethal effects of high power ultrasound on Rb cells. At low US powers, which alone did not seem to cause significant cell death, the addition of MB exacerbated the toxic effect of US. The size and number of pores seen on SEM appear to increase as power is increased, which in turn, may account for the decrease in cell viability. Further experiments are aimed at identifying the optimal US/MB dose with minimal effect on cell viability and maximal effect on membrane permeability.
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