Sonoluminescence and acoustic emission spectra at different stages of cavitation zone development

Abstract

The way in which a cavitation zone develops in a focused pulsed ultrasound field is studied in this work. Sonoluminescence (SL), total hydrophone output and cavitation noise spectra have been recorded across a gradual, smooth increase in applied voltage. It is shown that the cavitation zone passes through a number of stages of evolution, according to increasing ultrasound intensity, decreasing pulse period and increasing ultrasound pulse duration. Sonoluminescence is absent in the first phase and the hydrophone output spectra consists of a main line with two or three harmonics whose intensity is much lower than that of the main (fundamental) line. The second stage sees the onset of SL whose intensity increases smoothly and is accompanied by the appearance of higher harmonics and subharmonics in the cavitation noise spectra. In some cases, the wide-band (WBN) component can be seen in noise spectra during the final part of the second stage. In the third stage, SL intensity increases significantly and often quite sharply, while WBN intensity increases in the same manner. This is accompanied by a synchronous increase in the absorption of ultrasound by the cavitation zone, which is manifested in a sharp decrease in the hydrophone output. In the fourth stage, both SL and WBN intensities tend to decrease despite the increased voltage applied to the transducer. Furthermore, the fundamental line tends to decrease in strength as well, despite the increasing ultrasound intensity. The obtained results clearly identify the different stages of cavitation zone development using cavitation noise spectra analyses. We then hypothesize that three of the above stages may be responsible for three known types of ultrasound action on biological cells: damping viability, reversible cell damage (sonoporation) and irreversible damage/cytotoxicity.3

Insight into ultrasound-mediated reactive oxygen species generation by various metal-porphyrin complexes

“…In their work, the authors presented an intracellular cavitation mechanism to explain some US biological effects, from delicate and reversible bioeffects [71], to complete membrane disruption and irreversible cellular damage [72]. Moreover, in a previous work, we ourselves have shown that the cavitation zone passes through a number of stages of evolution and SL seems to develop accordingly [27]. In this scenario, it is not unreasonable to assume that the intracellular cavitation mechanism might also elicit an intracellular cavitation zone with different stages of evolution that are able to trigger our porphyrin compounds.…”

“…For some researchers, acoustic cavitation is an extreme phenomenon that is responsible for generating excessive vibration, erosion, reduced hydraulic performance and structural damage [22], while, for others, it is seen as an enormous concentration of energy with a wide range of unexplored chemical and physical consequences [23,24]. In particular, the emission of SL [25][26][27] has been proposed as the pivotal trigger for the sonosensitiser-mediated generation of reactive oxygen species (ROS) in SDT [28,29]. This hypothesis was formulated because most of the chemical compounds used in SDT are also photosensitisers [14].…”

WITHDRAWN: Low-Intensity Pulsed Ultrasound-Generated Singlet Oxygen Induces Telomere Damage Leading to Glioma Stem Cell Awakening From Quiescence

“…The previous literature generally believed that ultrasound induced sonosensitizers to produce 1 O 2 due to acoustic cavitation and sonoluminescence (53)(54)(55), but this often requires a higher sound intensity beyond diagnostic dose ultrasound. Ultrasound, as a kind of material vibration wave, can form phonons at the level of protein macromolecules and cause phonon-electron coupling (56).…”

Low-intensity pulsed ultrasound-generated singlet oxygen induces telomere damage leading to glioma stem cell awakening from quiescence

“…The previous literature generally believed that ultrasound induced sonosensitizers to produce 1 O 2 owing to acoustic cavitation and sonoluminescence ( Dezhkunov et al., 2000 , 2018 ; Sazgarnia et al., 2013 ), but this often requires a higher sound intensity beyond diagnostic dose ultrasound. Ultrasound, as a kind of material vibration wave, can form phonons at the level of protein macromolecules and cause phonon-electron coupling ( Viani et al., 2014 ).…”