Free radical formation and cell lysis induced by ultrasound in the presence of different rare gases.

The effect of varying the temperature of cavitation bubbles in aqueous solutions of different rare gases on free radical formation and shearing stress induced by ultrasound was investigated. After sonication with 50kHz ultrasound the yield of hydroxyl radicals was measured by spin trapping with 5,5-dimethyl-1-pyrroline-N-oxide and the cell lysis of cultured mammalian cells was investigated. The hydroxyl radical yields were in the order Xe greater than Kr greater than Ar greater than Ne greater than He, in accord with the higher temperatures of the cavitation bubbles. However, cell lysis induced by shearing stress was the same for all of the rare gases, and independent of their thermal conductivity and the temperature of the cavitation bubbles.