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Ultrasound is a widely used diagnostic medical imaging modality, and its therapeutic potential has recently been reported. This study examined whether ultrasound irradiation causes nanobubble destruction and identified the most effective frequency and duration of ultrasound for doxorubicin delivery in rat liver under ultrasound-targeted nanobubble destruction. Rats underwent an intravenous nanobubble injection via the caudal vein. An ultrasound probe was applied to the rat liver. The rats were divided into different groups based on the frequency. Fluorescence images were acquired using an IVIS® system. Laboratory tests were performed to determine the serum levels of AST (aspartate aminotransferase), ALT (alanine aminotransferase), total bilirubin, and creatinine. Under ultrasound irradiation, more nanobubbles were destroyed, and the doxorubicin uptake was increased in the rat liver (P ＜ 0.05). The 5 MHz group showed an increased fluorescence efficiency in the liver (P ＜ 0.05). Based on the duration of ultrasound irradiation, the 5, 10, and 13 MHz groups showed an increased fluorescence efficiency in the liver compared to the control group (P ＜ 0.05). There was no significant difference between the 15- and 30-minute groups. The other organs showed no significant differences compared to the control group. The groups to which ultrasound was applied showed increased serum AST and ALT levels, but the effects did not last for 30 min. Ultrasound-targeted nanobubble destruction was effective for doxorubicin delivery in the rat liver. The most effective ultrasound frequency and irradiation duration were 5 MHz and 15 min, respectively.

Objectives:The single collector collision (SCC) model is a model that predicts the separation efficiency of particles based on the collision efficiency between microbubbles and particles in the particle separation process. In order to remove micro-plastics (MPs) particles, which have recently been known to be harmful, we tried to analyze the impact and separation efficiency of MPs based on the SCC model and evaluate its application feasibility. Methods:Based on the SCC model, the collision efficiency prediction for MPs particle removal was simulated and the separation efficiency was evaluated. In addition, a series of flotation experiments were conducted using a flotation device that injects microbubbles to remove MPs particles suspended in water, and the experimental results and predicted values were compared. Results and Discussion:Using the SCC model, the collision efficiency according to the size distribution of MPs particles was not significantly different from that of typical particles (clay, kaolin) in water. Based on this collision efficiency, the maximum removal efficiency of MPs particles separated from the water body is predicted to reach about 90%. On the other hand, the initial collision-adhesion coefficient () of the MPs particles based on the SCC model was 0.03 to 0.1, showing a slight difference from the clay particles having the range of 0.3 to 0.4. The flotation separation efficiency of the MPs particles evaluated and predicted by applying this initial collision-adhesion coefficient showed a range similar to the measured value. In addition, the particle separation efficiency according to the increase of the measured bubble volume concentration to improve the particle separation efficiency also showed a pattern similar to the predicted value. Conclusions:In the flotation process, the initial collision-adhesion efficiency of the MPs particles predicted by the SCC model was lower than that of the kaolin particles. Based on the simple and simple model SCC theory, it was confirmed that it can be applied to the flotation separation analysis of MPs particles.