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. 2016 Aug 22;113(36):9983–9988. doi: 10.1073/pnas.1606915113

Fig. 2.

Fig. 2.

Individual ultrasound-stimulated microbubble oscillation increases endothelial membrane permeability. (A) Select frames from an ultrahigh-speed recording from the UPMC-Cam at 10.86 Mfps, highlighting microbubble spherical oscillation at 1 MHz and 0.8 MPa. (Scale bar, 5 µm.) (B) Quantification of the radial profile of the microbubble shown in A over time and (C) corresponding radial power spectrum as extracted from the UPMC-Cam bright-field recording. This microbubble exhibits some gas loss due to ultrasound (US) exposure, resulting in a slightly smaller size (1.4-µm radius) by the end of the US pulse and up to 3 min thereafter. (D) Simultaneous epifluorescence imaging before, during, and after US delivery highlights the uptake of a normally cell-impermeable model drug PI (red). The first two frames depict the microbubble–cell geometry (white lines denote cell contours and arrowheads denote microbubble location) in bright-field and epifluorescence frames, respectively. Frames 3–10 demonstrate PI uptake after US delivery. The commencement of PI uptake is spatially localized to the position of bubble–cell contact (arrowhead), entering the cytoplasm and continuing to diffuse within the nucleus. Frames 11 and 12, taken during calcein-specific imaging (green) before US (frame 11) and about 200 s later (frame 12), illustrate that calcein is lost during this sonoporation process. (Scale bar, 5 µm.) Note the characteristic differences in PI uptake dynamics within (E) the cytoplasm and (F) the nucleus, likely related to the diffusion physics of these two cellular compartments. The cytoplasmic PI profile is consistent with the arrest of PI entry within the cell (e.g., pore resealing, PI saturation), whereas the monotonically increasing, plateau-like nature of the nuclear PI reflects the immobile nature of the DNA within the nuclear cavity. (G and H) The range of PI uptake curves exhibited by all microbubbles interrogated at 1 MHz. These curves are normalized to their respective baseline-subtracted values. See Movies S1 and S2.