Enhancement and control of acoustic cavitation yield by low-level dual frequency sonication: A subharmonic analysis

Abstract

Evaluation of inertial cavitation is a significant problem where this mechanism of action is responsible for therapeutic applications such as drug delivery. It has shown that using multiple frequencies one is able to enhance and control induced cavitation. In this study, we used different sonication frequencies as 28 kHz, 130 kHz, 1 MHz, 3 MHz and their dual combinations to enhance acoustic cavitation. At each frequency, two different intensities were used and the subharmonic amplitude of each frequency in combinations was measured. It was observed that in combinations which include 28 kHz, the cavitation activity is enhanced. The 28 kHz subharmonic amplitude was used to compare these protocols in their ability to enhance cavitation. Besides, the area of cavitation damage was determined using an aluminum foil. Our results showed that the inertial cavitation activity increased at higher intensities and there is a significant correlation between the subharmonic amplitude and sonication intensity at each frequency (R>0.90). In addition, simultaneous combined dual-frequency orthogonal sonication at 28 kHz with other frequencies used can significantly increase the inertial cavitation activity as compared to the algebraic sum of the individual ultrasound irradiations in 28 kHz subharmonic frequency. The 28 kHz subharmonic amplitude for 28 kHz (0.04 W/cm(2)) and 3 MHz (2 and 1 W/cm(2)) combined dual frequency were about 4.6 and 1.5 times higher than that obtained from the algebraic sum of 28 kHz and 3 MHz irradiation, respectively. Also the 28 kHz subharmonic amplitude for combination of 28 kHz (0.04 W/cm(2)) and 1 MHz (2 and 1 W/cm(2)) were about 2.4 and 1.6 times higher than that obtained with their algebraic sum. Among different combinations, the continuous mode for two ultrasound sources of 28 kHz (0.04 W/cm(2)) and 3 MHz (2 W/cm(2)) is more effective than other combinations (p-value<0.05). The results of effective irradiation area showed no damaged aluminum foil in MHz sonication alone. However, there is significant difference between the effective irradiation area of combined dual frequency 28 kHz and 3 MHz with other irradiation modes (p-value<0.05) and it is limited locally.

In vitro stimulation of calcium overload and apoptosis by sonodynamic therapy combined with hematoporphyrin monomethyl ether in C6 glioma cells

“…In addition, Zhai et al (27) and Ninomiya et al (28) showed an inhibitory effect on growth of cancer cells induced by SDT when changing the ultrasound parameters to a frequency of 0.5–1.5 MHz and intensities of 0.4–460 W/cm 2 in vitro (27,28). The lower the frequency and intensity, the higher the cavitation effect and fewer side effects for the healthy surrounding tissue (8,19,20). Therefore, SDT in combination with HMME and the optimized ultrasound parameters of 1.0 W/cm 2 , 0.5 MHz and 60 sec were applied to the C6 glioma cells in the present study.…”

“…Honda et al (17) found a transient increase in [Ca 2+ ] i from outside the cells in human myelomonocytic lymphoma U937 cells following ultrasound alone, and Li et al (18) showed an increased [Ca 2+ ] i , released from internal stores at an ultrasound frequency of 1 MHz in combination with HMME in C6 glioma cells (18). This may be attributed to the ultrasonic cavitation effect, which changes the permeability of the cytomembrane (19,20). Therefore, overloaded [Ca 2+ ] i may be obtained from internal and external sources during the apoptotic process in C6 glioma cells, as a result of low-level ultrasound and HMME.…”

“…Previous studies have demonstrated the SDT may induce apoptosis in C6 glioma cells via the excessive production of ROS, which was due to the interaction of the ultrasonic cavitation and sensitizers (7–9,19,20). The oxidizing effect may damage mitochondria and lead to apoptosis via the mitochondrial signaling pathway (10–16).…”

Rapid skin permeabilization by the simultaneous application of dual-frequency, high-intensity ultrasound

“…Specifically, higher frequencies of US (>0.7 MHz) are capable of nucleating a relatively large number of small cavitation bubbles, relative to low-frequency US. Along these lines, recent reports have shown that by combining US horns operating at frequencies in the range of 20 kHz to 3 MHz, acoustic cavitation activity is enhanced compared to that of single US frequencies operating alone[5], [10], [11]. Here, we hypothesize that the addition of a second, high-frequency, US horn oriented parallel to the surface of the skin will nucleate a greater number of bubbles in the vicinity of the skin (see Figure 1a).…”

Comparing the in vivo sonodynamic effects of dual- and single-frequency ultrasound in breast adenocarcinoma

“…Kanthale et al [33] demonstrated that dual-frequency sonication results in the formation of a greater number of active bubbles at a higher collapse temperature when compared with a single-frequency operation, which enhances cytotoxic effects. Different frequency stimulation also contributes to a large variety of bubbles [34,35], which potentially enhances cell death by producing free radicals using a sonosensitizer drug [32]. It has been shown that inertial cavitation is enhanced during dual-frequency sonication, and when inertial cavitation is produced in a liquid, non-inertial cavitation occurs simultaneously [10,31].…”