Shen Yajing, Zhang Zhenhai, Fukuda Toshio
Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Hong Kong, People's Republic of China.
Nanotechnology. 2015 Apr 17;26(15):155702. doi: 10.1088/0957-4484/26/15/155702. Epub 2015 Mar 23.
Bending of nanopipette tips during cell penetration is a major cause of cell injection failure. However, the flexural rigidity of nanopipettes is little known due to their irregular structure. In this paper, we report a quantitative method to estimate the flexural rigidity of a nanopipette by investigating its bending spring rate. First nanopipettes with a tip size of 300 nm are fabricated from various glass tubes by laser pulling followed by focused ion beam (FIB) milling. Then the bending spring rate of the nanopipettes is investigated inside a scanning electron microscope (SEM). Finally, a yeast cell penetration test is performed on these nanopipettes, which have different bending spring rates. The results show that nanopipettes with a higher bending spring rate have better cell penetration capability, which confirms that the bending spring rate may well reflect the flexural rigidity of a nanopipette. This method provides a quantitative parameter for characterizing the mechanical property of a nanopipette that can be potentially taken as a standard specification in the future. This general method can also be used to estimate other one-dimensional structures for cell injection, which will greatly benefit basic cell biology research and clinical applications.
纳米移液器尖端在细胞穿刺过程中的弯曲是导致细胞注射失败的主要原因。然而，由于其结构不规则，纳米移液器的抗弯刚度鲜为人知。在本文中，我们报告了一种通过研究纳米移液器的弯曲弹簧常数来估算其抗弯刚度的定量方法。首先，通过激光拉制然后聚焦离子束（FIB）铣削，从各种玻璃管中制造出尖端尺寸为300 nm的纳米移液器。然后，在扫描电子显微镜（SEM）内研究纳米移液器的弯曲弹簧常数。最后，对这些具有不同弯曲弹簧常数的纳米移液器进行酵母细胞穿刺测试。结果表明，具有较高弯曲弹簧常数的纳米移液器具有更好的细胞穿刺能力，这证实了弯曲弹簧常数可以很好地反映纳米移液器的抗弯刚度。该方法为表征纳米移液器的机械性能提供了一个定量参数，未来有可能作为标准规范。这种通用方法还可用于估算细胞注射的其他一维结构，这将极大地有益于基础细胞生物学研究和临床应用。
