A novel procedure for pre-embedding double immunogold-silver labeling at the ultrastructural level

Area of Science:

• Immunocytochemistry
• Electron Microscopy
• Neuroscience

Background:

• Pre-embedding double immunogold-silver labeling is challenging due to the lack of methods to distinguish labels from identical sized gold conjugates.
• Previous techniques lacked the ability to differentiate labels when using ultrasmall gold conjugates of similar sizes.

Purpose of the Study:

• To investigate the feasibility of creating particle size segregation between two ultrasmall gold conjugates.
• To develop a pre-embedding immunogold-silver labeling protocol for precise subcellular co-localization of multiple antigens.

Main Methods:

• Sequential immunogold incubations and silver enhancements were employed.
• Two primary antibodies (mouse anti-synaptophysin and rabbit anti-glial fibrillary acidic protein (GFAP)) were used in a model system.
• Differentiation was achieved by single or double silver enhancement of ultrasmall gold conjugates.

Main Results:

• Two distinct populations of silver-enhanced particles (smaller, single-enhanced; larger, double-enhanced) were successfully created.
• Electron microscopy confirmed readily distinguishable particle sizes with minimal overlap within appropriate subcellular structures.
• The ultrastructure quality allowed for the identification of most subcellular organelles.

Conclusions:

• This study presents the first pre-embedding immunogold-silver labeling protocol capable of precise subcellular co-localization of multiple antigens.
• The developed method effectively differentiates labels using ultrasmall gold conjugates of identical sizes.
• This technique significantly advances the capability for multi-antigen detection at the subcellular level.