Dual-frequency ultrasound activation of nanomicellar doxorubicin in targeted tumor chemotherapy

Introduction: This study investigated the therapeutic effect of dual-frequency sonication (3 MHz and 28 kHz) at low intensity levels in combination with micellar doxorubicin in the treatment of a tumor model of spontaneous breast adenocarcinoma in Balb/c mice.

Methods: We used sonication frequencies 28 kHz and 3 MHz and their dual combinations in the progressive wave mode to enhance acoustic cavitation. Then, the antitumor effect of the simultaneous dual-frequency ultrasound (28 kHz and 3 MHz) at low intensity levels in combination with doxorubicin and micellar doxorubicin injection was investigated in a spontaneous model of breast adenocarcinoma in Balb/c mice. Sixty-three tumor-bearing mice were randomly divided into seven groups: control, sham, sonication with dual frequency, doxorubicin without sonication, doxorubicin with dual-frequency sonication, micellar doxorubicin without sonication, and micellar doxorubicin with dual-frequency sonication. The tumor volume change relative to the initial volume, tumor growth inhibition ratio, the required times for each tumor to reach two (T 2) and five (T 5) times its initial volume, and survival period were the tumor growth delay parameters which were calculated and recorded at various times after treatment.

Results: The results of the combination of frequencies 28 kHz (0.04 W/cm(2)) and 3 MHz (2.00 W/cm(2)) showed remarkable enhancement of the cavitation activity compared with single-frequency sonication (P < 0.05). The micellar doxorubicin injection with sonication group showed a significant difference in the relative volume percent parameter compared with the other groups (P < 0.05). Additionally, the T 2 and T 5 times in the micellar doxorubicin with sonication group were significantly higher than in the other groups (P < 0.05). Also, the survival period of the mice in the micellar doxorubicin with sonication group was significantly longer than in the other groups (P < 0.05). These findings were verified histopathologically.

Conclusion: This study shows that simultaneous combined dual-frequency ultrasound sonication in continuous mode is effective in producing cavitation activity at low intensity. We conclude that dual-frequency sonication with micellar doxorubicin injection extends survival in a murine breast adenocarcinoma model.