High-Resolution Bulgeless Liquid-Cell Electron Microscopy

07 February 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Liquid cell electron microscopy (LCEM) has long suffered from irreproducibility and its inability to confer high-quality images over a wide field of view. LCEM demands the encapsulation of the in-liquid sample between two ultrathin membranes (windows). In the vacuum environment of the electron microscope, the windows bulge, drastically reducing the achievable resolution and the usable viewing region. Herein, we introduce a shape-engineered nanofluidic cell architecture and an air-free drop-casting sample loading technique, which combined, provide robust bulgeless imaging conditions. We demonstrate the capabilities of our approach through the study of in-liquid model samples and quantitative measurements of the liquid layer thickness. The presented LCEM method confers high throughput, lattice resolution across the complete viewing window, and sufficient contrast for the observation of unstained liposomes, paving the way to high-resolution movies of biospecimens in their near native environment.

Keywords

Liquid cell electron microscopy

Supplementary materials

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Supplemental Information
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Supplemental Information including methods.
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Supplementary Movie 1
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Illustration of the nanofluidic cell assembly process.
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Supplementary Movie 2
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Au nanorods imaged at 200 kV near the corner of the viewing area. Magnification = 74kx. Dose rate ≈ 15 electrons Å-2 s-1.
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Supplementary 3
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Au nanorods imaged at 200 kV near the centre of the viewing area. Magnification = 94kx. Dose rate ≈ 25 electrons/(Å^2 s).
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Supplementary Movie 4
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Au nanorods imaged at 300 kV near the centre of the viewing area. Magnification = 450kx. Dose rate ≈ 7000 electrons/(Å^2 s). We observe nanoparticle sintering and facet formation.
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Supplementary Movie 5
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Au nanorods imaged at 200 kV illustrating electron beam induced dendritic-like growth. Magnification = 244k. Dose rate ≈ 130 electrons/(Å^2 s).
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Supplementary Movie 6
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Au nanorods imaged at 200 kV illustrating the electron beam induced formation of bubbles under prolonged imaging conditions. Magnification = 224kx. Dose rate ≈ 130 electrons/(Å^2 s).
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Supplementary Movie 7
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DOPC liposomes imaged at 200 kV near the centre of the viewing area. Magnification = 22kx. Dose rate ≈ 1.5 electrons/(Å^2 s). We observed unstained liposomes observed with sufficient contrast and their beam induced structural degradation over the course of approximately one minute.
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Supplementary Movie 8
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Au nanorods imaged at 300 kV with high resolution near the centre of the viewing area. Magnification = 600kx. Dose rate ≈ 12000 electrons electrons/(Å^2 s). We observed lattice planes and nanoparticle growth.
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