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Purpose: We want to compare the synergistic effect of low-intensity, dual-frequency (dual) ultrasound (US), applied in a repetitive sonication mode, and acoustically active lipospheres (AALs) containing doxorubicin (DOX) in a murine model (Balb/C)., Subjects and Methods: The tumor-bearing mice were divided into nine groups, namely two untreated groups (control and sham), and seven experimental groups, including treated with dual-frequency US (150 kHz continuous + 1MHz pulse ), triple exposure (3×30min) dual-frequency US, DOX (2 mg/kg intravenous), DOX in combination with single exposure (30 min) to dual-frequency US (drug + dual), DOX in combination with triple (3 × 30 min) exposure to dual-frequency US (drug + dual [REP]), AALs containing the drug-loaded (AAL), and a group receiving AAL in combination with single exposure (30 min) dual-frequency US (AAL + dual), respectively., Results: The effectiveness of DOX on tumor growth was enhanced by a factor of three when combined with the triple exposures of dual US (drug + dual [REP]). This combination protocol further increased the times needed for each tumor to 2 and 7 times its initial volume, respectively by 94% and 36% compared to the drug group. During the 30 days, following the treatment of tumors, the relative volume of tumors in AAL group was 118% less than that of the drug group. The survival rate of the groups treated with drug and AAL + dual was increased by 78.7% and 167% compared with sham, respectively., Conclusion: Although as a short treatment, a major improvement in treatment was observed by (drug + dual [REP]) compared with other treatments, the AAL + dual treatment compared with (drug + dual [REP]) showed an increase in the survival rates, hence more preferable over long periods., Competing Interests: None

Perfluorocarbon nanoemulsions are a new class of multifunctional stimuli-responsive nanocarriers which combine the properties of passive-targeted drug carriers, ultrasound imaging contrast agents, and ultrasound-responsive drug delivery systems. Doxorubicin-loaded alginate stabilized perflourohexane (PFH) nanodroplets were synthesized via nanoemulsion preparation method and their ultrasound responsivity, imaging, and therapeutic properties were studied. Doxorubicin was loaded into the nanodroplets (39.2nm) with encapsulation efficiency of 92.2%. In vitro release profile of doxorubicin from nanodroplets was an apparently biphasic release process and 12.6% of drug released from nanodroplets after 24h incubation in PBS, pH=7.4. Sonication with 28kHz therapeutic ultrasound for 10min triggered droplet-to-bubble transition in PFH nanodroplets which resulted in the release of 85.95% of doxorubicin from nanodroplets. Microbubbles formed by acoustic vaporization of the nanodroplets underwent inertial cavitation. In the breast cancer mice models, ultrasound-mediated therapy with doxorubicin-loaded PFH nanodroplets showed excellent anti-cancer effects characterized by tumor regression. Complete tumor regression was observed for the group in which doxorubicin-loaded nanodroplets were combined with ultrasound, whereas the tumor growth inhibition of doxorubicin -loaded nanodroplets was 89.6%. These multifunctional nanodroplets, with excellent therapeutic and ultrasound properties, could be promising drug delivery systems for chemotherapeutic application., (Copyright © 2016 Elsevier B.V. All rights reserved.)

In the present study the effect of process (homogenization speed) and formulation (polymer-alginate-concentration, surfactant concentration, drug amount, perfluorohexane volume fraction and co-surfactant inclusion) variables on particle size, entrapment efficiency, and drug release kinetics of doxorubicin-loaded alginate stabilized perfluorohexane nanodroplets were evaluated. Particle size and doxorubicin entrapment efficiency were highly affected by formulation and process variables. Increase in homogenization speed resulted in significant decrease in particle size and increase in entrapment efficiency. Polymer concentration and perfluorohexane amount both had similar effect on particle size. Particle size increased by an increase in the amount of both. Entrapment efficiency increased by increasing polymer concentration. In case of surfactant concentration and drug amount, particle size and entrapment efficiency had optimum values and an increase in concentration of both of them behind a certain limit resulted in increase in particle size and decrease in doxorubicin entrapment. In vitro release profile of doxorubicin was an apparently biphasic release process and 7%-13% of drug released after 24h incubation in PBS, pH=7.4, depending on the nanodroplets composition but ultrasound exposure for 10min resulted in triggered release of 85.95% of doxorubicin from optimal formulation (formulation E1 with 39.2nm diameter size and 92.2% entrapment efficiency)., (Copyright © 2016 Elsevier B.V. All rights reserved.)

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., (Copyright © 2011 Elsevier B.V. All rights reserved.)