These particles are ideal markers in the localisation of cellular components and antigenic sites due to the electron opaque properties of the gold nanoparticles. They are ideal for multiple labelling by using different sized particles to identify different targets.Optimal size. Smaller particles bind in higher numbers than larger particles but are harder to visualise. The best choice for EM is 10nm and these will contrast with 5, 20 or 40nm for double labelling.
Light Microscopy / In situ hybridisation.
The primary antibody step is followed by gold nanoparticle (immunogold) labelling. This in turn is followed by a sliver enhancement step producing a black macroscopic image at the site of the primary antibody.
Optimal size. Smaller particles (5nm) are the best for maximal labelling of tissue sections as their visualisation is amplified by the silver staining.
Western blots probed with primary antibody can be developed with a first step of immunogold labelling followed by silver enhancement to give a high contrast black signal for a positive result.
Optimal size. Larger nanoparticles (20 or 40nm) are best for macrocsopic imaging followed by silver enhancement.
In vitro Diagnostics.
The optimal size of gold nanoparticles for lateral flow tests are the larger 40nm size as they give the best pink macroscopic image.