Simple and Rapid Conductive Preparation of Wet Biological Samples for SEM Observation: Use of an Asymmetrical Choline-like Room Temperature Ionic Liquid as a Visualizing Agent

Abstract

In this study, we prepared a hydrophilic, choline-like room temperature ionic liquid (RTIL), and investigated its use as an electroconductive pretreatment for scanning electron microscopy (SEM) investigations of wet biological samples. Wet biological samples generally require pretreatment before SEM observation because of their properties. Conventional pretreatment methods consist of multiple tedious steps that take from several hours, to a day or more. In contrast, our pretreatment only requires the samples to be immersed in an RTIL. This gives the sample suitable electroconductivity for SEM analysis, which can then be carried outperformed rapidly. In addition, samples pretreated with RTILs can remain wet even in the vacuum chamber of SEM. This property allows morphological observation of wet biological samples in "a life-like manner" because our method avoids the chemical fixation, dehydrogation and drying processes required by conventional pretreatment. Moreover, some samples can be successfully visualized after pretreatment using RTILs without dilution. These results suggest that this method can allow simple and rapid conductive pretreatment of wet biological and insulating samples without optimizing their concentrations.