Zou Penglin, Li Mengqi, Wang Ziqi, Zhang Guoxiu, Jin Lifang, Pang Yan, Du Lianfang, Duan Yourong, Liu Zhaomiao, Shi Qiusheng
Department of Ultrasound, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
College of Mechanical Engineering and Applied Electronics Technology, Beijing University of Technology, Beijing, China.
Front Pharmacol. 2020 Jan 28;10:1651. doi: 10.3389/fphar.2019.01651. eCollection 2019.
The flow fields generated by the acoustic behavior of microbubbles can significantly increase cell permeability. This facilitates the cellular uptake of external molecules in a process known as ultrasound-mediated drug delivery. To promote its clinical translation, this study investigated the relationships among the ultrasound parameters, acoustic behavior of microbubbles, flow fields, and delivery results. SonoVue microbubbles were activated by 1 MHz pulsed ultrasound with 100 Hz pulse repetition frequency, 1:5 duty cycle, and 0.20/0.35/0.70 MPa peak rarefactional pressure. Micro-particle image velocimetry was used to detect the microbubble behavior and the resulting flow fields. Then HeLa human cervical cancer cells were treated with the same conditions for 2, 4, 10, 30, and 60 s, respectively. Fluorescein isothiocyanate and propidium iodide were used to quantitate the rates of sonoporated cells with a flow cytometer. The results indicate that (1) microbubbles exhibited different behavior in ultrasound fields of different peak rarefactional pressures. At peak rarefactional pressures of 0.20 and 0.35 MPa, the dispersed microbubbles clumped together into clusters, and the clusters showed no apparent movement. At a peak rarefactional pressure of 0.70 MPa, the microbubbles were partially broken, and the remainders underwent clustering and coalescence to form bubble clusters that exhibited translational oscillation. (2) The flow fields were unsteady before the unification of the microbubbles. After that, the flow fields showed a clear pattern. (3)The delivery efficiency improved with the shear stress of the flow fields increased. Before the formation of the microbubble/bubble cluster, the maximum shear stresses of the 0.20, 0.35, and 0.70 MPa groups were 56.0, 87.5 and 406.4 mPa, respectively, and the rates of the reversibly sonoporated cells were 2.4% ± 0.4%, 5.5% ± 1.3%, and 16.6% ± 0.2%. After the cluster formation, the maximum shear stresses of the three groups were 9.1, 8.7, and 71.7 mPa, respectively. The former two could not mediate sonoporation, whereas the last one could. These findings demonstrate the critical role of flow fields in ultrasound-mediated drug delivery and contribute to its clinical applications.
微泡的声学行为所产生的流场可显著提高细胞通透性。在一个被称为超声介导药物递送的过程中，这有助于细胞摄取外部分子。为推动其临床转化，本研究调查了超声参数、微泡的声学行为、流场和递送结果之间的关系。用1MHz的脉冲超声激活声诺维微泡，脉冲重复频率为100Hz，占空比为1:5，峰值负压为0.20/0.35/0.70MPa。采用微粒图像测速技术检测微泡行为及由此产生的流场。然后分别在相同条件下对HeLa人宫颈癌细胞处理2、4、10、30和60秒。用异硫氰酸荧光素和碘化丙啶通过流式细胞仪定量声孔化细胞的比率。结果表明：（1）微泡在不同峰值负压的超声场中表现出不同行为。在峰值负压为0.20和0.35MPa时，分散的微泡聚集成簇，且这些簇没有明显移动。在峰值负压为0.70MPa时，微泡部分破裂，剩余部分聚并形成表现出平移振荡的气泡簇。（2）在微泡合并之前，流场不稳定。在此之后，流场呈现出清晰的模式。（3）递送效率随着流场剪应力的增加而提高。在微泡/气泡簇形成之前，0.20、0.35和0.70MPa组的最大剪应力分别为56.0、87.5和406.4mPa，可逆声孔化细胞的比率分别为2.4%±0.4%、5.5%±1.3%和16.6%±0.2%。在簇形成之后，三组的最大剪应力分别为9.1、8.7和71.7mPa。前两者不能介导声孔化，而最后一个可以。这些发现证明了流场在超声介导药物递送中的关键作用，并有助于其临床应用。
