Department of Physics, The Norwegian University of Science and Technology, Trondheim, Norway.
Ultrasound Med Biol. 2012 Mar;38(3):476-86. doi: 10.1016/j.ultrasmedbio.2011.11.017. Epub 2012 Jan 21.
The ultrasound exposure parameters that maximize drug release from dierucoyl-phosphatidylcholine (DEPC)-based liposomes were studied using two transducers operating at 300 kHz and 1 MHz. Fluorescent calcein was used as a model drug, and the release from liposomes in solution was measured using a spectrophotometer. The release of calcein was more efficient at 300 kHz than at 1 MHz, with thresholds of peak negative pressures of 0.9 MPa and 1.9 MPa, respectively. Above this threshold, the release increased with increasing peak negative pressure, mechanical index (MI), and duty cycle. The amount of drug released followed first-order kinetics and increased with exposure time to a maximal release. To increase the release further, the MI had to be increased. The results demonstrate that the MI and the overall exposure time are the major parameters that determine the drug's release. The drug's release is probably due to mechanical (cavitation) rather than thermal effects, and that was also confirmed by the detection of hydroxide radicals.
研究了两种分别在 300 kHz 和 1 MHz 下工作的换能器，以确定从二油酰基磷脂酰胆碱（DEPC）基脂质体中最大程度释放药物的超声暴露参数。使用荧光钙黄绿素作为模型药物，并用分光光度计测量脂质体在溶液中的释放情况。在 300 kHz 下，钙黄绿素的释放比在 1 MHz 下更有效，其峰值负压阈值分别为 0.9 MPa 和 1.9 MPa。超过此阈值后，随着峰值负压、机械指数（MI）和占空比的增加，释放量也随之增加。药物的释放遵循一级动力学，随着暴露时间的增加而达到最大释放量。为了进一步增加释放量，必须增加 MI。结果表明，MI 和总暴露时间是决定药物释放的主要参数。药物的释放可能是由于机械（空化）而不是热效应引起的，通过检测氢氧化物自由基也得到了证实。
