Artificial Cavitation Research Articles

Enhancement of ultrasound-mediated transfection with cavitation micronuclei

Many methods are available for transferring foreign genes into mammalian cells (transfection). The advantages of ultrasound-mediated transfection are that it can be controlled in both space, by focusing, and time, by exposure. It was tested whether ultrasound-mediated gene transfection in cultured immortalized human chondrocytes would be enhanced using artificial cavitation nuclei in the form of Albunex®. Here 1.0 MHz ultrasound transmitted through the bottoms of six-well culture plates containing media with green fluorescent protein reporter gene plasmids at a concentration of 40 μg/ml and Albunex® at 50×106 bubbles/ml produced a peak transfection efficiency of about 50% of the living cells when exposure was 4×105 P spatial average peak pressure (SAPP) for 20 mins. Using these parameters, transfection efficiency increased linearly with ultrasound exposure pressure with a transfection threshold observed at a SAPP of 105 P. Adding fresh Albunex® at 50×106 bubbles/ml prior to sequential one second 3.2 or 4.0×105 P exposures increased transfection efficiency by 15% for each of three consecutive exposures. Efficient in vitro and perhaps in vivo transfection appears possible with ultrasound providing both temporal and spatial control over the transfection process.

Artificial Cavitation Nuclei Significantly Enhance Acoustically Induced Cell Transfection

The efficiency of ultrasound-mediated gene transfection was enhanced three- to fourfold, compared to previous results, through the use of green fluorescent protein reporter gene, cultured immortalized human chondrocytes and artificial cavitation nuclei in the form of Albunex®. Cells were exposed to 1.0-MHz ultrasound transmitted through the bottom of six-well culture plates containing immortalized chondrocytes, media, DNA at a concentration of 40 μg/mL and Albunex® at 50 × 10 6 bubbles/mL. Transfection efficiency increased linearly with ultrasound exposure pressure with a transfection threshold observed at a spatial average peak positive pressure (SAPP) of 0.12 MPa and reaching about 50% of the living cells when exposed to 0.41 MPa SAPP for 20 s. Adding fresh Albunex® at 50 × 10 6 bubbles/mL prior to sequential 1-s, 0.32- or 0.41-MPa exposures increased transfection with each exposure, reaching 43% transfection after four exposures. Efficient in vitro and in vivo transfection now appear possible with these enhancements.

Mechanism of cavitation development in the pine wilt disease

AbstractVolatile terpenes increase in xylem tissue after infection of Pinus thunbergii with the pine wood nematode (Bursaphelenchus xylophilus). The role of these terpenes in traeheid cavitation, which blocks xylem‐sap ascent and leads to water deficit in pine trees, was assessed. Volatile terpene concentration increased long before initiation of tracheid cavitation. After the volatile terpenes reached the highest concentration, severe cavitation developed. Direct injection of α‐pinene into healthy pine trunks formed artificial cavitation in xylem. These observations support the hypothesis that excessively produced volatiles, which are hydrophobic and have lower surface tension than water can promote tracheid cavitation in pine wilt disease.

Acoustic scattering from transient, micron‐sized cavitation bubbles

If cavitation occurs in vivo due to the application of medical ultrasound, it is likely to be difficult to observe. Concern rests less with the destruction of biological cells and more with the more subtle subcellular injuries that could result in damage to components responsible for cell reproduction. Cavitation on the scale of single biological cells—microcavitation—can be observed in vitro by scattering high‐frequency ultrasound (30 MHz) off of single transient cavitation bubbles. An active cavitation detection (ACD) has been used to determine the onset conditions (e.g., cavitation thresholds) in vitro for water with various artificial cavitation nuclei. More recently, the same scattering technique has been employed to observe the radius versus time characteristics of transient cavitation bubbles of one or more cycles. Reports on both threshold measurements and attempts to measure quantitative radius versus time histories of individual bubbles will be presented. The results will be presented in the general context of the joint Yale‐National Center for Physical Acoustics collaborative effort to assess the safety of diagnostic ultrasound. [Work supported by the National Institutes of Health through Grant 4R01‐CA39374.]

A possible mechanism for the emergence of auto-oscillations in developed artificial cavitation flows and immersed gas jets

A possible mechanism for the emergence of auto-oscillations in developed artificial cavitation flows and immersed gas jets

Artificial cavitation flow behind a slender wedge on the lower surface of a horizontal wall

1. The problem, considered in [1], is posed of cavitation flow past a slender wedge (bump) consisting of a flat plate mounted at the small angle a to a wall. In contrast with [1], the ratio of the cavity length L to the wedge lengtha1 is considered to be arbitrary. To study this flow we use a modification of the Ryabushinskii scheme (Fig. 1, curve 1), in which the length b1 of the fictitious wedge which closes the cavity is assumed small in comparison with the bump lengtha1. Here the angleβ at which the surface of the fictitious wedge approaches the horizontal wall is not specified ahead of time.