Colloidal Gold, or more precisely gold nanoparticles are sub-micrometer sized particles or nanoparticles of gold, usually found in the form of a suspension in water hence the name “colloid”, in which case the liquid usually appears to be either an intense red color ( for particles less than 100 nm).

The particles are conjugated to monoclonal antibodies via ionic interactions at the FC region of the IG antibodies where three amino acids, lysine, tryptophan and cysteine are found. This results in an antibody-gold conjugate, which, when captured by the pre-coated-antibodies on the NC Membrane will show the distinctive redline.