A comparative review of cryo-electron ptychography: Biological applications and future perspectives

Electron ptychography is an advanced four-dimensional scanning transmission electron microscopy technique that demonstrates significant advantages in revealing ultra-high-resolution atomic structures through computational phase retrieval in materials science while offering potential benefits for radiation-sensitive biological specimens. Recent advancements in hybrid pixel array detectors and computational algorithms have enabled low-dose imaging, demonstrating the feasibility of imaging frozen-hydrated biological samples, termed cryo-electron ptychography. Nevertheless, challenges such as low-dose constraints and complexities in computational and experimental setups currently limit the widespread adoption of cryo-electron ptychography and achievable resolution beyond the subnanometer level. This review examines the progress in cryo-electron ptychography, identifies the challenges that distinguish biological specimens from radiation-tolerant samples, and assesses potential future developments in algorithms and hardware that could unlock its capabilities for structural analysis of biomacromolecules and in situ subcellular structures.