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Safety of diagnostic ultrasound
Published in Peter R Hoskins, Kevin Martin, Abigail Thrush, Diagnostic Ultrasound, 2019
Of course, the existence of an oscillating bubble (i.e. a hazard) does not automatically result in a risk. It is necessary to relate its behaviour with something that could be potentially damaging. When a suspension of cells is exposed to ultrasound and stable cavitation occurs, shear stresses may be sufficient to rupture the cell membranes. Shear is a tearing force, and many biological structures are much more easily damaged by tearing than by compression or tension. Destruction of blood cells in suspension by ultrasound may occur in this way provided that the acoustic pressure is high enough, and this has been shown in vitro for erythrocytes, leucocytes and platelets. In addition, the existence of a second effect, not causing cell destruction, may occur. Gaps can open transiently in the cell membrane during ultrasound exposure, allowing the passage of larger biomolecules such as DNA, an effect known as ‘sonoporation’.
New Approaches for High-Speed, High-Resolution Imaging
Published in Laurent A. Francis, Krzysztof Iniewski, Novel Advances in Microsystems Technologies and Their Applications, 2017
Gil Bub, Nathan Nebeker, Roger Light
High-speed communication in excitable cell networks may represent the fastest events generated by living cells, but there are other biophysical processes that can take advantage of high-speed imaging technologies. Bubble formation in living tissue is an example of a process that is important in several biomedical applications. Bubble-enhanced sonoporation is a process where cell membranes are ruptured in a controlled way to enhance delivery of pharmacological agents. Ultrasound-driven bubbles have been used to enhance contrast during ultrasonic imaging, allowing real-time evaluation of myocardial function. Similarly, shock waves created by bubble formation play a role in kidney stone treatments [8]. Bubble formation and destruction are extremely rapid events, and experimental investigation requires imaging rates approaching 1,000,000 fps.
Ultrasound-Responsive Nanomedicine
Published in Lin Zhu, Stimuli-Responsive Nanomedicine, 2021
Tyrone M. Portera, Jonathan A. Kopechek
Microbubbles respond more strongly to ultrasound compared to tissue due to the high compressibility of their gas core. As microbubbles are insonified, the ultrasound pressure waves cause compression and expansion of the microbubbles during each acoustic cycle (Fig. 8.2). When driven at relatively low-pressure amplitudes, oscillating microbubbles radiate pressure waves, which are used in diagnostic ultrasound to enhance contrast in the images. When driven at higher pressures, microbubbles undergo large amplitude oscillations, known as “cavitation.” The oscillations become non-linear at moderate acoustic pressures and eventually the microbubble can collapse due to the inertia of the surrounding fluid (“inertial cavitation”). Cavitation can induce microstreaming and microjetting in the surrounding fluid [23–25], which can have profound effects on nearby structures. For example, ship propellers can be damaged by long-term cavitation activity occurring in near proximity. In biology, microstreaming and microjetting can stimulate bioeffects that can transiently enhance vascular permeability [26, 27] and can also transiently porate cell membranes, a phenomenon known as “sonoporation” [28, 29]. The small pores formed in cell membranes during sonoporation provide a temporary window for direct delivery of molecular therapeutics (such as drugs or genes) before the pores are repaired by the cell (Fig. 8.3) [30]. A range of pore sizes can occur, but pores with diameters of approximately 100–200 nm have been reported [31]. In addition to sonoporation, cavitation has also been shown to enhance endocytosis [32, 33].
Ultrasound-triggered imaging and drug delivery using microbubble-self-aggregate complexes
Published in Journal of Biomaterials Science, Polymer Edition, 2022
In Jae Chung, Hyungwon Moon, Seong Ik Jeon, Hak Jong Lee, Cheol-Hee Ahn
Through the sonoporation effect, the improvement of local delivery can be achieved by simple co-administration of drugs and MBs. It was reported that the delivery efficiency can be furtherly improved when drugs are directly conjugated to MBs or loaded in MB-based carriers, reducing systemic side effects [14]. In our previous study, the MB-liposome complex was evaluated to treat brain tumors [15]. Doxorubicin, a water-soluble anticancer drug, was successfully loaded in the liposome and the liposome was conjugated stably on the surface of MBs. When loading hydrophobic drugs such as Paclitaxel or Docetaxel (DTX), however, liposome was not a suitable carrier since its core was hydrophilic. Although it has been reported that hydrophobic drugs can be loaded in the shell of liposomes [16,17], their loading amount was limited due to the thickness of the shell and the rigidity of the lipid alkyl chain [18].
Pulsed ultrasound-assisted extraction of natural antioxidants from mandarin (Citrus deliciosa Tenore) leaves: Experimental and modeling study
Published in Chemical Engineering Communications, 2018
Selin Şahin, Zeynep İlbay, Ş. İsmail Kırbaşlar
Novel separation technologies including ultrasound-assisted extraction (UAE) are of great value to the “green” processes with an increased mass and heat transfer, reduced equipment size in addition to being inexpensive, easy to set up, time saving, and environmentally friendly process with a safe solvent (Jacotet-Navarro et al., 2016). Therefore, UAE is one of the green processes to extract high added value compounds from plant materials as an alternative to conventional ones, overcoming the degradation problems as well as consumption of too much time and energy (Li et al., 2013). The success of this method depends on several individual and combined mechanisms such as fragmentation, erosion, capillary effect, detexturation, and sonoporation (Chemat et al., 2017). Fragmentation favors the complete extraction by maximizing the surface area leading to higher mass transfer (Clodoveo et al., 2017). Erosion produced by ultrasonic cavitation, which leads to locally high temperatures, locally high pressures, and free radicals (Johansson et al., 2016). The capillary effect of ultrasound also improves the mass transfer by increasing the penetration rate of liquid into the pores of material (Chemat et al., 2017). Detexturation also known as disruption of cell walls is another phenomenon of enhancing mass transfer across cell membranes (Wang and Yuan, 2016). Sonoporation is formed by bubbles of ultrasound for the permeability of cell membranes, favoring the drug delivery (Fix et al., 2017).