用于组织样品冷冻电子断层成像的冷冻提取(Cryo-lift-out)技术
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北京大学生命科学学院,北京 100871

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国家自然科学基金(32230051)资助项目。


Cryo-lift-out Technique for Cryo-electron Tomography of Tissue Samples
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School of Life Sciences, Peking University, Beijing 100871, China

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This work was supported by a grant from The National Natural Science Foundation of China (32230051).

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    摘要:

    冷冻电子断层成像术(cryo-electron tomography,cryo-ET)能够在近生理状态下,解析细胞内大分子复合物的高分辨率三维结构,为理解生命过程提供关键的结构基础。然而,许多关键的生物学过程并非在孤立的细胞中发生,而是源于组织内或细胞间的复杂相互作用。而且,许多研究对象无法通过单细胞培养获得,如神经组织、肿瘤组织、植物组织、病理样本等,因此,只能通过直接从个体或组织层面解剖取样来进行研究。将cryo-ET的应用从单细胞水平推进至更复杂的组织层面,对于在原生环境中理解完整的生命活动至关重要。基于冷冻聚焦离子束(cyro-focused ion beam,cryo-FIB)发展的冷冻提取(cryo-lift-out)技术,作为大尺寸组织样品冷冻透射电子显微镜薄片制备的核心技术,其流程烦琐易错,且对操作者经验依赖性极强,尚未实现大规模普及应用。本文系统回顾了冷冻提取技术的发展历程,详细阐述了其技术流程,并通过与材料科学中常温提取技术的对比,剖析了冷冻提取技术中的关键难点与相应解决策略,最后对该技术的未来发展方向进行了展望。对冷冻提取技术的系统剖析,有助于明确其规模化应用的关键制约因素,并为后续的方法优化与技术革新奠定基础。

    Abstract:

    Cryo-electron tomography (cryo-ET) enables the determination of high-resolution three-dimensional structures of macromolecular complexes within cells in a near-physiological state, providing crucial structural insights into fundamental life processes. Cryo-ET has achieved landmark successes in single-cell models. However, many critical biological processes do not occur in isolated cells but emerge from intercellular coordination within tissues. Furthermore, many research subjects, including neural tissues, tumor biopsies, plant tissues, and clinical pathological samples, cannot be obtained through single-cell culture and must be directly dissected from organisms or tissue blocks. Advancing cryo-ET from single-cell to tissue-level applications is therefore crucial for capturing the full complexity of biological activities in their native context. A major technical bottleneck for tissue cryo-ET lies in the preparation of sufficiently thin (<300 nm) lamellae from vitrified tissue specimens. Although high-pressure freezing can vitrify tissues up to 200 μm thick, these samples are far too thick for direct transmission electron microscopy imaging. Among the available thinning methods, cryo-focused ion beam (cryo-FIB) milling has emerged as the most promising approach, as it avoids the mechanical artifacts inherent to cryo-ultramicrotomy. However, conventional on-the-grid cryo-FIB milling is inefficient for thick tissues, requiring excessive milling time and discarding most of the sample. To overcome these limitations, cryo-lift-out has been developed—a technique in which a micromanipulator physically extracts a chunk of interest from deep within the tissue and transfers it to a dedicated grid for final thinning. This approach bypasses the thickness barrier and enables site-specific analysis of internal structures. This review systematically traces the evolution of cryo-lift-out from its origins in materials science to its adaptation for biological tissues. In room-temperature lift-out, reliable attachment is achieved by gas-injection system (GIS)-assisted metal deposition. Transferring this approach to cryogenic conditions proved challenging because precursor gases condense on all cold surfaces, leading to contamination and poor adhesion. The development of copper-assisted redeposition marked a critical turning point: instead of relying on gas deposition, this method uses ion-beam sputtering to deposit copper atoms at the needle-chunk interface, creating a strong, low-contamination bond. This innovation has enabled robust cryo-lift-out workflows and paved the way for serial lift-out, in which multiple consecutive lamellae are prepared from a single tissue chunk, substantially increasing throughput and enabling volumetric imaging. Despite these advances, several technical challenges remain. Curtaining effects caused by uneven chunk surfaces can introduce artifacts into tomograms, requiring careful optimization of milling parameters and protective coating. The cryo-adhesion step still demands precise control of beam angle, needle positioning, and milling depth, making the process highly operator-dependent. Additionally, the choice of grid geometry is critical. Custom-designed grids with double-sided attachment improves stability and offer better compatibility with cryo-ET tilt series. Automation, which has greatly improved room-temperature lift-out, has not yet been achieved for cryo-lift-out due to the complexity of handling heterogeneous biological tissues and the need for real-time adaptation. Future progress will likely focus on integrating cryo-lift-out with volume electron microscopy to correlate ultrastructure across scales, developing intelligent control systems to reduce user intervention, and extending the technology to challenging samples such as plant tissues and some material science samples for interface study. A systematic analysis of the cryo-lift-out technique clarifies the key limiting factors for its large-scale application and lays a foundation for methodological refinement and technological innovation. By consolidating recent advances and identifying remaining bottlenecks, this review aims to support the broader adoption of cryo-lift-out and accelerate the development of tissue-scale in situ structural biology.

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秦昌东,郭强,高宁.用于组织样品冷冻电子断层成像的冷冻提取(Cryo-lift-out)技术[J].生物化学与生物物理进展,2026,53(6):1503-1519 QIN Chang-Dong, GUO Qiang, GAO Ning. Cryo-lift-out Technique for Cryo-electron Tomography of Tissue Samples[J]. Progress in Biochemistry and Biophysics,2026,53(6):1503-1519

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  • 收稿日期:2025-12-22
  • 最后修改日期:2026-04-18
  • 录用日期:2026-04-09
  • 在线发布日期: 2026-04-09
  • 出版日期: 2026-06-28
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