bubble dynamics; ultrasonic drug release; polymeric micelles
We have reported the ability of Pluronic P-105 micelles to sequester anthracycline drugs and release their contents upon application of 70 kHz ultrasound (US)1 (Figure 1). Optimal targeting to tumors depends on focus and control of US insonation, which is better achieved at higher frequencies. While no evidence of in vitro drug release was found at 500 kHz, drug release at 70 kHz correlates with the intensity of the subharmonic signal in the acoustic spectrum generated by the insonated bubbles2(Figure 2). Having established that bubble oscillations (cavitation) are directly related to drug release at 70 kHz, we now investigate the differences in the dynamics of oscillating bubbles at both frequencies.