Grid Staining and Contrast Enhancement

This training activity provides theoretical and practical instruction in staining and contrast enhancement procedures for biological samples prepared for transmission electron microscopy.

Biological materials are mainly composed of light elements and therefore generally show low intrinsic contrast under the electron beam. Contrast enhancement procedures increase electron scattering and improve the visualization of membranes, organelles, macromolecular complexes and other cellular structures.

The training covers:

• Correct handling of TEM grids

• Selection of appropriate grid supports and coatings

• Preparation and filtration of staining solutions

• Positive staining of ultrathin sections

• Use of heavy-metal contrast agents

• Sequential contrasting procedures

• Control of staining time and solution conditions

• Washing and drying of grids

• Prevention of precipitates and contamination

• Evaluation of staining quality

• Identification of common contrasting artefacts

• Safe handling and disposal of hazardous reagents

Participants are introduced to commonly used contrast-enhancement procedures involving uranyl-based stains and lead salts, as well as alternative contrasting reagents when required by laboratory protocols or safety regulations.

Particular attention is paid to avoiding contamination from carbon dioxide, dust particles, stain precipitates and inadequate washing, all of which can interfere with image quality and ultrastructural interpretation.

At the end of the activity, participants will be able to prepare and contrast TEM grids correctly, optimize staining conditions and assess whether the contrast obtained is appropriate for electron microscopy analysis.