An international collaborative research group led by Associate Professor Hideki Ishida of the Graduate School of Natural Science and Technology at Shimane University has developed a new method for scanning electron microscopy (SEM) observation that enables the observation of biological samples with well-preserved fine structures using a freeze-drying method employing only water, without any chemical fixatives. The research was published in Scientific Reports.
Ishida, H., Fukuda, N., Shimada, M. et al. Artifact-free preparation of biological samples for SEM by optimized water freeze-drying. Sci Rep 16, 717 (2026) CC BY-NC-ND 4.0.
SEM is an essential tool for high-resolution observation of the external morphology of organisms, but there have been significant problems in sample preparation when observing delicate, soft cells such as Paramecium (protozoa). Conventional sample preparation methods cause artificial structural changes (artifacts) that shrink cells or destroy fine structures (such as cilia) through chemical fixation and alcohol dehydration. Furthermore, the method of freeze-drying water directly has generally been considered inappropriate due to the possibility of cell structure damage by ice crystals.
The research group has now overturned conventional wisdom and enabled artifact-free sample observation by significantly optimizing the freezing process of water freeze-drying. Specifically, they standardized the procedure of rapidly freezing a suspension of live cells through precise contact with a copper block cooled to minus 80 degrees Celsius via a PVC guide tube. This significantly increased the success rate of obtaining artifact-free samples from the rate of approximately 10% using conventional methods.
Furthermore, the time required from freezing to completion of drying was shortened to just 2 to 3 hours. This enables highly accurate observation of external morphology at low cost and high-speed using dry ice and a general-purpose vacuum pump, even without special cryogenic equipment.
This method is available even for laboratories without special cryogenic equipment. It is expected to shorten sample preparation time in morphological research, dramatically improve observation accuracy, and contribute to a wide range of life science fields such as cell biology and taxonomy.
Journal Information
Publication: Scientific Reports
Title: Artifact-free preparation of biological samples for SEM by optimized water freeze-drying
DOI: 10.1038/s41598-025-30335-4
This article has been translated by JST with permission from The Science News Ltd. (https://sci-news.co.jp/). Unauthorized reproduction of the article and photographs is prohibited.