Frequency-Dependent Evaluation of the Role of Definity in Producing Sonoporation of Chinese Hamster Ovary Cells

Abstract

Objectives Sonoporation uses ultrasound (US) and ultrasound contrast agents (UCAs) to enhance cell permeabilization, thereby allowing delivery of therapeutic compounds non-invasively into specific target cells. The objective of this study was to elucidate the biophysical mechanism of sonoporation, specifically the role of UCAs as well as exposure frequency. The inertial cavitation (IC) thresholds of the lipid-shelled octafluoropropane UCA were directly compared to the levels of generated sonoporation to determine the involvement of UCAs in producing sonoporation. Methods Chinese hamster ovary cells were exposed as a monolayer in a solution of the UCA, 500,000-Da fluorescein isothiocyanate-dextran, and phosphate-buffered saline to 30 seconds of pulsed US (pulse duration, 5 cycles; pulse repetition frequency, 10 Hz) at 3 frequencies (0.92, 3.2, and 5.6 MHz). The peak rarefactional pressure (Pr) was varied over a range from 4 kPa to 4.1 MPa, and 5 to 7 independent replicates were performed at each pressure. Results The experimental observations demonstrated that IC was likely not the physical mechanism for sonoporation. Sonoporation activity was observed at pressure levels below the threshold for IC of the UCA (1.27 ± 0.32 MPa at 0.92 MHz, 0.84 ± 0.19 MPa at 3.2 MHz, and 2.57 ± 0.26 MPa at 5.6 MHz) for all 3 frequencies examined. The Pr values at which the peak sonoporation activity occurred were 1.4 MPa at 0.92 MHz, 0.25 MPa at 3.2 MHz, and 2.3 MPa at 5.6 MHz. The UCA collapse thresholds followed a similar trend. A 1-way analysis of variance test confirmed that sonoporation activity differed among the 3 frequencies examined (P = 10−8). Conclusions These results thus suggest that sonoporation is related to linear and/or nonlinear oscillation of the UCA occurring at pressure levels below the IC threshold.

Nanoparticle-assisted ultrasound: A special focus on sonodynamic therapy against cancer

“…Even if the biophysical mechanism that results in the enhancement of the cell membrane permeability under ultrasound needs further elucidation, it was reported that sonoporation is not due to inertial cavitation, but to micro-streaming and shear stresses related to stable oscillations [56,57]. In in-vitro experiments the dissolved gas in the culture medium is sufficient so that the sonication itself generates cavitation bubbles.…”

Advanced Interfere Treatment of Diabetic Cardiomyopathy Rats by aFGF-Loaded Heparin-Modified Microbubbles and UTMD Technique

“…Therefore, MB can be used for cardiovascular diseases [14]. In addition, ultrasound targeted microbubble destruction (UTMD) technique can provide a cavitationfacilitated drug absorption promoting effect, thus realizing targeted delivery of bioactive agents to cardiac tissue [15][16][17][18][19][20]. UTMD technique may therefore serve as a valuable tool to further improve the cardiac specificity and efficacy of aFGF application for DCM patients.…”

Spiral computed tomography evaluation of rabbit VX2 hepatic tumors treated with 20 kHz ultrasound and microbubbles

“…US at 20 kHz is applied not only in industry but also to improve the in vitro and in vivo bio-effects in medicine (9)(10)(11). In vitro studies have demonstrated that 20 kHz US enhances the permeation of diclofenac sodium across EpiDerm™ 5-fold (9)(10)(11).…”

“…In vitro studies have demonstrated that 20 kHz US enhances the permeation of diclofenac sodium across EpiDerm™ 5-fold (9)(10)(11). It is a unique and exciting theranostic modality that can be used to track drug carriers, trigger drug release and improve drug deposition to tumor cells with high spatial precision (9).…”

“…It is a unique and exciting theranostic modality that can be used to track drug carriers, trigger drug release and improve drug deposition to tumor cells with high spatial precision (9). Cavitation bubbles induced by 20 kHz US may induce cell death or transient membrane permeabilization, which is defined as sonoporation on a single cell level (10). Microscopy disclosed that the collapse of a microbubble (MB) and generation of a jet produce small holes within cell membranes (12).…”