Examination of Inertial Cavitation of Optison in Producing Sonoporation of Chinese Hamster Ovary Cells

Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
Ultrasound in medicine & biology (Impact Factor: 2.21). 08/2008; 34(12):2009-18. DOI: 10.1016/j.ultrasmedbio.2008.05.003
Source: PubMed


The objective of this project was to elucidate the relationship between ultrasound contrast agents (UCAs) and sonoporation. Sonoporation is an ultrasound-induced, transient cell membrane permeability change that allows for the uptake of normally impermeable macromolecules. Specifically, this study will determine the role that inertial cavitation plays in eliciting sonoporation. The inertial cavitation thresholds of the UCA, Optison, are compared directly with the results of sonoporation to determine the involvement of inertial cavitation in sonoporation. Chinese hamster ovary (CHO) cells were exposed as a monolayer in a solution of Optison, 500,000 Da fluorescein isothiocyanate-dextran (FITC-dextran), and phosphate-buffered saline (PBS) to 30 s of pulsed ultrasound at 3.15-MHz center frequency, 5-cycle pulse duration and 10-Hz pulse repetition frequency. The peak rarefactional pressure (P(r)) was varied over a range from 120 kPa-3.5 MPa, and five independent replicates were performed at each pressure. As the P(r) was increased, from 120 kPa-3.5 MPa, the fraction of sonoporated cells among the total viable population increased from 0.63-10.21%, with the maximum occurring at 2.4 MPa. The inertial cavitation threshold for Optison at these exposure conditions has previously been shown to be in the range 0.77-0.83 MPa, at which sonoporation activity was found to be 50% of its maximum level. Furthermore, significant sonoporation activity was observed at pressure levels below the threshold for inertial cavitation of Optison. Above 2.4 MPa, a significant drop in sonoporation activity occurred, corresponding to pressures where >95% of the Optison was collapsing. These results demonstrate that sonoporation is not directly a result of inertial cavitation of the UCA, rather that the effect is related to linear and/or nonlinear oscillation of the UCA occurring at pressure levels below the inertial cavitation threshold.

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Available from: Ryan Lawrence Steinberg, May 14, 2015
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    • "In this framework, microscopic and spectroscopic techniques offer the sensitivity and capability to detect morphological, structural and functional fine alterations of sonicated cells, as they are not yet significantly advanced [22] [23] [24] [25] [26] [27]. In previous papers [28] [29], we have shown how the effects of US on biological samples can be effectively revealed by means of Fourier Transform Infrared (FTIR) spectroscopy, a non-destructive technique which is able to monitor conformational and functional changes exhibited by specific subsets of macromolecules inside a cell population. "
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    ABSTRACT: This work is focused on the in vitro study of the effects induced by medical ultrasound (US) in murine fibroblast cells (NIH-3T3) at a low-intensity of exposure (spatial peak temporal average intensity Ita<0.1Wcm(-)(2)). Conventional 1MHz and 3MHz US devices of therapeutic relevance were employed with varying intensity and exposure time parameters. In this framework, upon cells exposure to US, structural changes at the molecular level were evaluated by infrared spectroscopy; alterations in plasma membrane permeability were monitored in terms of uptake efficiency of small cell-impermeable model drug molecules, as measured by fluorescence microscopy and flow cytometry. The results were related to the cell viability and combined with the statistical PCA analysis, confirming that NIH-3T3 cells are sensitive to therapeutic US, mainly at 1MHz, with time-dependent increases in both efficiency of uptake, recovery of wild-type membrane permeability, and the size of molecules entering 3T3. On the contrary, the exposures from US equipment at 3MHz show uptakes comparable with untreated samples.
    Ultrasonics 12/2013; 54(4). DOI:10.1016/j.ultras.2013.12.003 · 1.94 Impact Factor
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    • "Additional sonoporation mechanisms such as the push and pulling behaviour resultant from the expansion and compression phase of microbubble oscillations near a membrane [12], [25], and acoustic microstreaming [26] are also thought to generate transient micropores through which a therapeutic agent can pass. Pores can also be generated by the formation of micro-jets by a microbubble undergoing non-spherical shape oscillations near a cell [27], which can result in non-viable cells and may not be useful for therapy in which the target cells must survive [28]. Phospholipid-encapsulated microbubbles typically have a polydisperse size distribution over the 1-10 µm range and can be functionalised for molecular targeting as well as loaded with drug-carrying liposomes [29], [30]. "
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    ABSTRACT: The therapeutic use of microbubbles for targeted drug or gene delivery is a highly active area of research. Phospholipid- encapsulated microbubbles typically have a polydisperse size distribution over the 1 to 10 μm range and can be functionalized for molecular targeting and loaded with drugcarrying liposomes. Sonoporation through the generation of shear stress on the cell membrane by microbubble oscillations is one mechanism that results in pore formation in the cell membrane and can improve drug delivery. A microbubble oscillating at its resonant frequency would generate maximum shear stress on a membrane. However, because of the polydisperse nature of phospholipid microbubbles, a range of resonant frequencies would exist in a single population. In this study, the use of linear chirp excitations was compared with equivalent duration and acoustic pressure tone excitations when measuring the sonoporation efficiency of targeted microbubbles on human colorectal cancer cells. A 3 to 7 MHz chirp had the greatest sonoporation efficiency of 26.9 ± 5.6%, compared with 16.4 ± 1.1% for the 1.32 to 3.08 MHz chirp. The equivalent 2.2- and 5-MHz tone excitations have efficiencies of 12.8 ± 2.1% and 15.6 ± 1.1%, respectively, which were all above the efficiency of 4.1 ± 3.1% from the control exposure.
    IEEE transactions on ultrasonics, ferroelectrics, and frequency control 12/2013; 60(12):2511-20. DOI:10.1109/TUFFC.2013.2850 · 1.51 Impact Factor
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    • "This work assumes nuclei for bubble activity originate from UCA rupture. The encapsulating shell of an UCA will rupture when subjected to sufficient tension, thereby releasing the encapsulated gas (Forbes et al 2008, Yeh and Su 2008, Chen et al 2003, Porter et al 2006, Sboros et al 2003, Guan and Matula 2004). The released gas either dissolves rapidly or coalesces due to secondary Bjerknes forces (Ammi 2006, Postema et al 2002). "
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    ABSTRACT: The mechanical index (MI) was formulated to gauge the likelihood of adverse bioeffects from inertial cavitation. However, the MI formulation did not consider bubble activity from stable cavitation. This type of bubble activity can be readily nucleated from ultrasound contrast agents (UCAs) and has the potential to promote beneficial bioeffects. Here, the presence of stable cavitation is determined numerically by tracking the onset of subharmonic oscillations within a population of bubbles for frequencies up to 7 MHz and peak rarefactional pressures up to 3 MPa. In addition, the acoustic pressure rupture threshold of an UCA population was determined using the Marmottant model. The threshold for subharmonic emissions of optimally sized bubbles was found to be lower than the inertial cavitation threshold for all frequencies studied. The rupture thresholds of optimally sized UCAs were found to be lower than the threshold for subharmonic emissions for either single cycle or steady state acoustic excitations. Because the thresholds of both subharmonic emissions and UCA rupture are linearly dependent on frequency, an index of the form I(CAV) = P(r)/f (where P(r) is the peak rarefactional pressure in MPa and f is the frequency in MHz) was derived to gauge the likelihood of subharmonic emissions due to stable cavitation activity nucleated from UCAs.
    Physics in Medicine and Biology 12/2012; 58(1):127-144. DOI:10.1088/0031-9155/58/1/127 · 2.76 Impact Factor
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