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We have previously applied ultrasound (US) with microbubbles (MBs) to enhance inner ear drug delivery, with most experiments conducted using single‐frequency, high‐power density US, and multiple treatments. In the present study, the treatment efficacy was enhanced and safety concerns were addressed using a combination of low‐power‐density, single‐transducer, dual‐frequency US (ISPTA = 213 mW/cm2) and MBs of different sizes coated with insulin‐like growth factor 1 (IGF‐1). This study is the first to investigate the drug‐coating capacity of human serum albumin (HSA) MBs of different particle sizes and their drug delivery efficiency. The concentration of HSA was adjusted to produce different MB sizes. The drug‐coating efficiency was significantly higher for large‐sized MBs than for smaller MBs. In vitro Franz diffusion experiments showed that the combination of dual‐frequency US and large MB size delivered the most IGF‐1 (24.3 ± 0.47 ng/cm2) to the receptor side at the second hour of treatment. In an in vivo guinea pig experiment, the efficiency of IGF‐1 delivery into the inner ear was 15.9 times greater in animals treated with the combination of dual‐frequency US and large MBs (D‐USMB) than in control animals treated with round window soaking (RWS). The IGF‐1 delivery efficiency was 10.15 times greater with the combination of single‐frequency US and large size MBs (S‐USMB) than with RWS. Confocal microscopy of the cochlea showed a stronger distribution of IGF‐1 in the basal turn in the D‐USMB and S‐USMB groups than in the RWS group. In the second and third turns, the D‐USMB group showed the greatest IGF‐1 distribution. Hearing assessments revealed no significant differences among the D‐USMB, S‐USMB, and RWS groups. In conclusion, the combination of single‐transducer dual‐frequency US and suitably sized MBs can significantly reduce US power density while enhancing the delivery of large molecular weight drugs, such as IGF‐1, to the inner ear. [ABSTRACT FROM AUTHOR]

Our previous study demonstrated that ultrasound is able to promote differentiation on neural stem cells (NSCs), and dual‐frequency ultrasound promotes this effect due to enhanced acoustic cavitation compared with single‐frequency ultrasound. However, the underlying biological reasons have not been well disclosed. The purpose of this study was to investigate the underlying bioeffects, mechanisms and signaling pathways of dual‐frequency ultrasound on NSC differentiation. The morphology, neurite outgrowth, and differentiation percentages were investigated under various dual‐frequency simulation parameters with exposure periods varying from 5 to 15 min. Morphological observations identified that dual‐frequency ultrasound stimulation promoted ultrasound dose‐dependent neurite outgrowth. In particular, cells exposed for 10 min/2 days showed optimal neurite outgrowth and neuron differentiation percentages. In addition, live cell calcium images showed that dual‐frequency ultrasound enhanced the internal calcium content of the cells, and calcium ions entering cells from the extracellular environment could be observed. Dual frequency ultrasound exposure enhanced extracellular calcium influx and upregulated extracellular signal‐regulated kinases 1/2 (ERK1/2) expression. Observations from immunostaining and protein expression examinations also identified that dual‐frequency ultrasound promoted brain‐derived neurotrophic factor (BDNF) secretion from astrocytes derived from NSCs. In summary, evidence supports that dual‐frequency ultrasound effectively enhances functional neuron differentiation via calcium channel regulation via the downstream ERK1/2 pathway and promotes BDNF secretion to serve as feedback to cascade neuron differentiation. The results may provide an alternative for cell‐based therapy in brain injury. [ABSTRACT FROM AUTHOR]

BACKGROUND: Ultrasound is widely used to accelerate many reactions and unit operations, but few studies have reported its effects on starch properties and structure. RESULTS: Corn starch suspended in ethanol solution was treated by dual-frequency ultrasound (DFU) and single-frequency ultrasound (SFU). Results showed that the transparency of the starch treated under 20 + 25 kHz DFU improved by 26.94% and 31.70%, respectively, compared to 20kHz and 25kHz SFU. Hardness, brittleness, elasticity, adhesiveness, conglutinationdegree, chewiness and recoverability of starch was reduced after ultrasonic treatment, and with increasing ultrasonic frequency these properties decreased. Its enthalpy value also decreased with ultrasound. Compared with each SFU treatment, enthalpy value decreased by 1.41% and 0.82%, respectively, by DFU. The freeze-thaw stability of starch was also weakened by ultrasound, which was obviously changed by DFU. Under ultrasound, the crystal structure of starch was not damaged, characteristic diffraction peak intensity was significantly reduced and diffuse diffraction features increased, exhibiting a decline in crystal lattice ordering degree. In comparison to SFU, DFU caused a pronounced reduction in starch crystallinity. CONCLUSION:After ultrasonic treatment, the transparencyof corn starchpaste improved, but itshardness, brittleness, elasticity, adhesiveness, conglutinationdegree, chewiness andrecoverabilitydecreased, aswell as starch crystallinity andenthalpy values. DFU was found to be more effective than SFU. [ABSTRACT FROM AUTHOR]

Effects on the structure and properties of sweet potato starch under single frequency ultrasound of 25, 80 kHz and dual-frequency ultrasound of 25 and 80 kHz were investigated at the same treating conditions else. Dents and pores were found by SEM at the surface of starch with both ultrasounds. Starch-iodine complex analysis showed above ultrasounds destroyed amylopectin and starch chains. FT-IR indicated that with ultrasonic treatments, the functional groups of starch were not destroyed, but its crystal structure was damaged. As a result, its crystalline index decreased. Brabender curves showed that the peak viscosity of starch with dual-frequency ultrasound was 14.09% lower than that of the native starch. In addition, the solubility and transmittance of starch increased by ultrasound, and the solubility went up as ultrasonication time was increased. It reached the maximum when the starch was treated for 60 min by dual-frequency ultrasound, which increased by 2.69% compared to that of native starch. The starch being treated by dual-frequency ultrasound for 30 min showed maximum transmittance, increasing it by 5.1% compared to the native starch; however, continuously increasing ultrasonic treatment resulted in a decrease of transmittance. Therefore, compared to single frequency ultrasound, dual-frequency ultrasonic treatment caused more obvious changes to the structure and properties. [ABSTRACT FROM AUTHOR]