Comprehensive Comparison Between STEM-HAADF and TEM Bright-field Mode for Imaging Resin Embedded Biological Samples

Area of Science:

• Electron microscopy
• Biological imaging
• Materials science

Background:

• Transmission electron microscopy (TEM) in bright-field mode is standard for resin-embedded biological samples.
• Modern TEMs offer scanning TEM (STEM) mode with high-angle annular dark-field (HAADF) detectors.
• Image quality in biological sample analysis is critical for accurate interpretation.

Purpose of the Study:

• To compare image quality between TEM bright-field and STEM-HAADF modes.
• To evaluate performance across diverse biological sample types (yeast, algae, plant, human, animal cells/tissues).
• To assess the impact of post-staining on image quality in both modes.

Main Methods:

• Resin-embedded biological samples were imaged using both TEM bright-field and STEM-HAADF modes.
• Sample types included Saccharomyces, Chlorella, Haematococcus, Nicotiana, MCF7 cells, and mouse liver/brain tissue.
• Image quality was assessed based on contrast, brightness, and signal-to-noise ratio.

Main Results:

• STEM-HAADF mode generally yielded superior image quality (contrast, brightness, signal-to-noise ratio).
• Samples without uranyl acetate or lead citrate post-staining showed significantly less graininess in STEM-HAADF mode.
• STEM-HAADF mode excelled with unstained algae, MCF7, and liver cells, and lacked artifacts seen in TEM mode.

Conclusions:

• STEM-HAADF mode presents significant advantages for imaging resin-embedded biological samples, especially those with low intrinsic contrast or unstained sections.
• This technique can potentially eliminate the need for post-staining in certain biological TEM applications.
• STEM-HAADF imaging improves the clarity and reliability of ultrastructural analysis in diverse biological specimens.