Nanoscale Surface Metal-Coating Method without Pretreatment for High-Magnification Biological Observation and Applications

Biospecimen imaging is essential across various fields. In particular, a considerable amount of research has focused on developing pretreatment techniques, ranging from freeze-drying to the use of highly conductive polymers, and on advancements in instrumentation, such as cryogenic electron microscopy. These specialized techniques and equipment have facilitated nanoscale and microscale bioimaging. However, user access to these environments remains limited. This study introduced a novel technique to achieve high conductivity in bioimaging by employing a magnetically controlled sputtering cathode to facilitate low-temperature deposition and low-electron bombardment. This approach allows for the convenient high-magnification observation of highly structured three-dimensional specimens, such as pill bugs and butterfly wings, and fragile specimens, such as single-cell protozoan parasites, using metal deposition only. Furthermore, it is easily accessible in the field of bioimaging because it does not require any pretreatment and enables surface analysis of biospecimens with an electron microscope using only a single pretreatment process. Protozoa, which are microorganisms, were successfully observed at high magnification without structural changes due to thermal denaturation. Furthermore, metallic film deposition and electrochemical signal measurements using these metallic films were achieved in pill bugs.