Chau Ying, Suen Wai Leung Langston, Tse Ho Yan, Wong Hoi Sang
Division of Biomedical Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong; Department of Chemical and Biomolecular Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
Department of Chemical and Biomolecular Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
Eur J Pharm Sci. 2017 Mar 30;100:273-279. doi: 10.1016/j.ejps.2017.01.016. Epub 2017 Jan 16.
We previously employed ultrasound as a needleless approach to deliver macromolecules via the transscleral route to the back of the eye in live animals (Suen et al., 2013). Here, we investigated the nature of the ultrasound-enhanced transport through sclera, the outermost barrier in the transscleral route. Thus, the possible role of cavitation from ultrasound was explored; its effect during and after sonication on scleral penetration was measured; and the dependence on the size of macromolecules was determined. We applied ultrasound frequency from 40kHz to 3MHz at I (spatial-average-temporal-average intensity) of 0.05W/cm to fresh rabbit sclera ex vivo. Fluorescent dextran of size 20kDa to 150kDa was used as macromolecular probes. We measured the distance of penetration of the probes through the sclera over 30s during sonication and over 15min after sonication from cryosectioned tissue images. Deeper penetration in the sclera was observed with decreasing frequency. The presence of stable cavitation was further verified by passive acoustic detection. The effect during sonication increased penetration distance up to 20 fold and was limited to macromolecular probes ≤70kDa. The effect post sonication increased penetration distance up to 3 fold and attributed to the improved intrasscleral transport of macromolecules ≥70kDa. Post-sonication enhancement diminished gradually in 3h. As the extent of cavitation increased with decreasing frequency, the trend observed supports the contribution of (stable) cavitation to enhancing transport through sclera. Effect during sonication was attributed to flow associated with acoustic microstreaming. Effect post sonication was attributed to the temporary increase in scleral permeability. Flow-associated effect was more pronounced but only applied to smaller macromolecules.
我们之前曾采用超声作为一种无针方法，通过经巩膜途径将大分子递送至活体动物的眼后段（Suen等人，2013年）。在此，我们研究了超声增强穿过巩膜（经巩膜途径中的最外层屏障）运输的性质。因此，我们探讨了超声空化的可能作用；测量了超声处理期间及之后其对巩膜穿透的影响；并确定了对大分子大小的依赖性。我们在体外将频率为40kHz至3MHz、空间平均时间平均强度（I）为0.05W/cm²的超声应用于新鲜兔巩膜。使用大小为20kDa至150kDa的荧光葡聚糖作为大分子探针。我们从冷冻切片组织图像中测量了超声处理期间30秒内以及超声处理后15分钟内探针穿过巩膜的穿透距离。随着频率降低，在巩膜中观察到更深的穿透。通过被动声学检测进一步证实了稳定空化的存在。超声处理期间的作用使穿透距离增加了20倍，且仅限于大小≤70kDa的大分子探针。超声处理后的作用使穿透距离增加了3倍，这归因于大小≥70kDa的大分子在巩膜内运输的改善。超声处理后的增强作用在3小时内逐渐减弱。由于空化程度随着频率降低而增加，观察到的趋势支持（稳定）空化对增强穿过巩膜运输的贡献。超声处理期间的作用归因于与声流相关的流动。超声处理后的作用归因于巩膜通透性的暂时增加。与流动相关的作用更明显，但仅适用于较小的大分子。
