Scavenging dissolved oxygen via acoustic droplet vaporization |
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| Institution: | 1. UCL Mechanical Engineering, University College London, London WC1E 7JE, United Kingdom;2. Center for Bionics, Biomedical Research Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea;1. Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA;2. Department of Urology, University of Washington, Seattle, Washington, USA;3. Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, USA;4. Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA;5. Division of Pediatric Cardiology, Department of Pediatrics and Communicable Diseases, University of Michigan, Ann Arbor, Michigan, USA;1. Department of Precision Engineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo, Japan;2. Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo, Japan;3. Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo, Japan;4. Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo, Japan;1. Applied Physics Program, University of Michigan, Ann Arbor, Michigan, USA;2. Department of Radiology, University of Michigan Health System, Ann Arbor, Michigan, USA;3. Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA;4. School of Dentistry, University of Michigan, Ann Arbor, Michigan, USA;5. Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan, USA |
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| Abstract: | Acoustic droplet vaporization (ADV) of perfluorocarbon emulsions has been explored for diagnostic and therapeutic applications. Previous studies have demonstrated that vaporization of a liquid droplet results in a gas microbubble with a diameter 5–6 times larger than the initial droplet diameter. The expansion factor can increase to a factor of 10 in gassy fluids as a result of air diffusing from the surrounding fluid into the microbubble. This study investigates the potential of this process to serve as an ultrasound-mediated gas scavenging technology. Perfluoropentane droplets diluted in phosphate-buffered saline (PBS) were insonified by a 2 MHz transducer at peak rarefactional pressures lower than and greater than the ADV pressure amplitude threshold in an in vitro flow phantom. The change in dissolved oxygen (DO) of the PBS before and after ADV was measured. A numerical model of gas scavenging, based on conservation of mass and equal partial pressures of gases at equilibrium, was developed. At insonation pressures exceeding the ADV threshold, the DO of air-saturated PBS decreased with increasing insonation pressures, dropping as low as 25% of air saturation within 20 s. The decrease in DO of the PBS during ADV was dependent on the volumetric size distribution of the droplets and the fraction of droplets transitioned during ultrasound exposure. Numerically predicted changes in DO from the model agreed with the experimentally measured DO, indicating that concentration gradients can explain this phenomenon. Using computationally modified droplet size distributions that would be suitable for in vivo applications, the DO of the PBS was found to decrease with increasing concentrations. This study demonstrates that ADV can significantly decrease the DO in an aqueous fluid, which may have direct therapeutic applications and should be considered for ADV-based diagnostic or therapeutic applications. |
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| Keywords: | Cavitation Dissolved oxygen Perfluorocabon droplets Particle sizing Ultrasound-mediated phase transition |
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