Ultrasound insonification of microbubbles can locally increase vascular permeability to enhance drug delivery. To control and optimize the therapeutic potential, we need to better understand the underlying biological mechanisms of the drug delivery pathways. The aim of this in vitro study was to elucidate the microbubble-endothelial cell interaction using the Brandaris 128 ultra-high-speed camera (up to 25 Mfps) coupled to a custom-built Nikon confocal microscope, to visualize both microbubble oscillation and the cellular response. Sonoporation and opening of cell-cell contacts by single αVβ3-targeted microbubbles (n = 152) was monitored up to 4 min after ultrasound insonification (2 MHz, 100-400 kPa, 10 cycles). Sonoporation occurred when microbubble excursion amplitudes exceeded 0.7 μm. Quantification of the influx of the fluorescent model drug propidium iodide upon sonoporation showed that the size of the created pore increased for larger microbubble excursion amplitudes. Microbubble-mediated opening of cell-cell contacts occurred as a cellular response upon sonoporation and did not correlate with the microbubble excursion amplitude itself. The initial integrity of the cell-cell contacts affected the susceptibly to drug delivery, since cell-cell contacts opened more often when cells were only partially attached to their neighbors (48%) than when fully attached (14%). The drug delivery outcomes were independent of nonlinear microbubble behavior, microbubble location, and cell size. In conclusion, by studying the microbubble-cell interaction at nanosecond and nanometer resolution the relationship between drug delivery pathways and their underlying mechanisms was further unraveled. These novel insights will aid the development of safe and efficient microbubble-mediated drug delivery.

中文翻译：

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由于声穿孔而使内皮细胞与细胞接触打开。

超声声化微气泡可以局部增加血管通透性，从而增强药物的递送。为了控制和优化治疗潜力，我们需要更好地了解药物输送途径的潜在生物学机制。这项体外研究的目的是通过使用Brandaris 128超高速相机（高达25 Mfps）和定制的尼康共聚焦显微镜来阐明微泡-内皮细胞之间的相互作用，以观察微泡振荡和细胞响应。在超声声化（2 MHz，100-400 kPa，10个周期）后直至4分钟，通过单个αVβ3靶向的微泡（n = 152）监测细胞的渗透和开放。当微泡偏移幅度超过0.7μm时发生声波震荡。超声处理后对荧光模型药物碘化丙啶的涌入量进行量化显示，对于较大的微气泡偏移幅度，创建的孔的大小会增加。微气泡介导的细胞-细胞接触的打开是声波穿透后的细胞反应，并且与微气泡偏移幅度本身不相关。细胞-细胞接触的初始完整性很容易影响药物传递，因为当细胞仅部分附着于其邻居时（48％）比完全附着（14％）时，细胞-细胞接触打开的频率更高。药物的输送结果与非线性微泡行为，微泡位置和细胞大小无关。结论，通过研究纳秒级和纳米级分辨率下的微气泡-细胞相互作用，进一步阐明了药物传递途径及其潜在机理之间的关系。这些新颖的见解将有助于开发安全有效的微泡介导的药物递送。