High-resolution imaging of living mammalian cells bound by nanobeads-connected antibodies in a medium using scanning electron-assisted dielectric microscopy

Tomoko Okada,Toshihiko Ogura

doi:10.1038/srep43025

Abstract

Nanometre-scale-resolution imaging technologies for liquid-phase specimens are indispensable tools in various scientific fields. In biology, observing untreated living cells in a medium is essential for analysing cellular functions. However, nanoparticles that bind living cells in a medium are hard to detect directly using traditional optical or electron microscopy. Therefore, we previously developed a novel scanning electron-assisted dielectric microscope (SE-ADM) capable of nanoscale observations. This method enables observation of intact cells in aqueous conditions. Here, we use this SE-ADM system to clearly observe antibody-binding nanobeads in liquid-phase. We also report the successful direct detection of streptavidin-conjugated nanobeads binding to untreated cells in a medium via a biotin-conjugated anti-CD44 antibody. Our system is capable of obtaining clear images of cellular organelles and beads on the cells at the same time. The direct observation of living cells with nanoparticles in a medium allowed by our system may contribute the development of carriers for drug delivery systems (DDS).

Highlights

Low radiation damage and high-contrast imaging without staining or fixation[24,25,26,27]
Our scanning electron-assisted dielectric microscopy (SE-ADM) system is based on a field-emission scanning electron microscope (FE-SEM) (Fig. 1a)
We have reported the successful direct observation of non-fluorescence 100-nm polystyrene beads binding to antibodies in aqueous condition by our SE-ADM system

Summary

Introduction

Low radiation damage and high-contrast imaging without staining or fixation[24,25,26,27]. Our system is capable of producing high-contrast images of untreated biological specimens in aqueous conditions[26,27]. Irradiated electrons are almost absorbed in a tungsten layer on the SiN thin film; the negative electric-field potential arises at this position[24]. This negative potential is detected at the bottom measurement terminal through the specimen in water. We firstly showed our SE-ADM system observing the untreated living mammalian cells under aqueous condition[27]. Here, we first report that the SE-ADM system is capable of observing antibody-binding nanoparticles in liquid-phase. We successfully observe nanobeads directly binding to mammalian cancer cells via antibodies in a medium and their intracellular structure at the same time

Results

Discussion

Conclusion