Takaku Yasuharu, Suzuki Hiroshi, Ohta Isao, Tsutsui Takami, Matsumoto Haruko, Shimomura Masatsugu, Hariyama Takahiko
Department of Biology, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu 431-3192, Japan CREST, Japan Science and Technology Agency, Hon-cho 4-1-8, Kawaguchi 332-0012, Japan.
Department of Chemistry, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu 431-3192, Japan.
Proc Biol Sci. 2015 Mar 7;282(1802). doi: 10.1098/rspb.2014.2857.
Although extremely useful for a wide range of investigations, the field emission scanning electron microscope (FE-SEM) has not allowed researchers to observe living organisms. However, we have recently reported that a simple surface modification consisting of a thin extra layer, termed 'NanoSuit', can keep organisms alive in the high vacuum (10(-5) to 10(-7) Pa) of the SEM. This paper further explores the protective properties of the NanoSuit surface-shield. We found that a NanoSuit formed with the optimum concentration of Tween 20 faithfully preserves the integrity of an organism's surface without interfering with SEM imaging. We also found that electrostatic charging was absent as long as the organisms were alive, even if they had not been coated with electrically conducting materials. This result suggests that living organisms possess their own electrical conductors and/or rely on certain properties of the surface to inhibit charging. The NanoSuit seems to prolong the charge-free condition and increase survival time under vacuum. These findings should encourage the development of more sophisticated observation methods for studying living organisms in an FE-SEM.
尽管场发射扫描电子显微镜（FE-SEM）在广泛的研究中极为有用，但它一直无法让研究人员观察活的生物体。然而，我们最近报道了一种简单的表面改性方法，即在生物体表面形成一层名为“纳米防护服”的超薄额外层，这能使生物体在扫描电子显微镜的高真空环境（10^(-5)至10^(-7)帕）中存活。本文进一步探究了纳米防护服表面屏蔽层的保护特性。我们发现，用最佳浓度的吐温20形成的纳米防护服能忠实地保持生物体表面的完整性，同时不干扰扫描电子显微镜成像。我们还发现，只要生物体存活，即使未用导电材料进行涂层处理，也不会产生静电充电现象。这一结果表明，活的生物体自身具备电导体和/或依赖表面的某些特性来抑制充电。纳米防护服似乎能延长无电荷状态并增加在真空中的存活时间。这些发现应会推动开发更先进的观察方法，以便在场发射扫描电子显微镜中研究活的生物体。
