Effect of local dual frequency sonication on drug distribution from polymeric nanomicelles

To overcome the side effects caused by systemic administration of doxorubicin, nanosized polymeric micelles were used in combination with dual frequency ultrasonic irradiation. These micelles release the drug due to acoustic cavitation, which is enhanced in dual frequency ultrasonic fields. To form the drug-loaded micelles, Pluronic P-105 copolymer was used, and doxorubicin was physically loaded into stabilized micelles with an average size of 14 nm. In this study, adult female Balb/C mice were transplanted with spontaneous breast adenocarcinoma tumors and were injected with a dose of 1.3 mg/kg doxorubicin in one of three forms: free doxorubicin, micellar doxorubicin without sonication and micellar doxorubicin with sonication. To increase cavitation yield, the tumor region was sonicated for 2.5 min at simultaneous frequencies of 3 MHz (I(SATA)=2 W/cm(2)) and 28 kHz (I(SATA)=0.04 W/cm(2)). The animals were sacrificed 24h after injection, and their tumor, heart, spleen, liver, kidneys and plasma were separated and homogenized. The drug content in the tissues was determined using tissue fluorimetry (350 nm excitation and 560 nm emission), and standard drug dose curves were obtained for each tissue. The results show that in the group that received micellar doxorubicin with sonication, the drug concentration in the tumor tissue was significantly higher than in the free doxorubicin injection group (8.69 times) and the micellar doxorubicin without sonication group (2.60 times). The drug concentration in other tissues was significantly lower in the micellar doxorubicin with sonication group relative to the free doxorubicin (3.35 times) and the micellar drug without sonication (2.48 times) groups (p<0.05). We conclude that dual frequency sonication improves drug release from micelles and increases the drug uptake by tumors due to sonoporation. The proposed drug delivery system creates an improved treatment capability while reducing systemic side effects caused by drug uptake in other tissues.