Detection of antibodies to the human immunodeficiency virus by a silver-enhanced gold-labelled immunosorbent assay

Silver enhancement of quantum dots resulting from (1) metabolism of toxic metals in animals and humans, (2) in vivo, in vitro and immersion created zinc–sulphur/zinc–selenium nanocrystals, (3) metal ions liberated from metal implants and particles

Autometallographic (AMG) silver enhancement is a potent histochemical tool for tracing a variety of metal containing nanocrystals, e.g. pure gold and silver nanoclusters and quantum dots of silver, mercury, bismuth or zinc, with sulphur and/or selenium. These nanocrystals can be created in many different ways, e.g. (1) by manufacturing colloidal gold or silver particles, (2) by treating an organism in vivo with sulphide or selenide ions, (3) as the result of a metabolic decomposition of bismuth-, mercury- or silver-containing macromolecules in cell organelles, or (4) as the end product of histochemical processing of tissue sections. Such nano-sized AMG nanocrystals can then be silver-amplified several times of magnitude by being exposed to an AMG developer, i.e. a normal photographic developer enriched with silver ions. The present monograph attempts to provide a review of the autometallographic silver amplification techniques known today and their use in biology. After achieving a stronghold in histochemistry by Timm's introduction of the "silver-sulphide staining" in 1958, the AMG technique has evolved and expanded into several different areas of research, including immunocytochemistry, tracing of enzymes at LM and EM levels, blot staining, retrograde axonal tracing of zinc-enriched (ZEN) neurons, counterstaining of semithin sections, enhancement of histochemical reaction products, marking of phagocytotic cells, staining of myelin, tracing of gold ions released from gold implants, and visualization of capillaries. General technical comments, protocols for the current AMG methods and a summary of the most significant scientific results obtained by this wide variety of AMG histochemical approaches are included in the present article.

A silver enhanced, gold labelled, immunosorbent assay for detecting antibodies to rubella virus

A silver enhanced, gold labelled, immunosorbent assay (SEGLISA) for the detection of IgG antibodies to the rubella virus in human serum was developed. Pre-coated microtitre wells are used as the immobilised base of rubella antigens on to which any rubella antibodies from patient samples will bind. This antigen/antibody complex is then visualised firstly by gold labelled anti-immunoglobulin G, which binds to any human IgG that may be present, and then by silver amplification, resulting in a black permanent deposit on the microtitre well surface. Patient samples (n = 121) were screened using a commercially available enzyme linked immunosorbent assay (ELISA) and an equivalent SEGLISA. Results were comparable but the SEGLISA does not have the disadvantages associated with enzyme labels. The silver deposit may also be read visually or the dried plate may be stored for future reference.

Use of a silver-enhanced gold-labelled immunoassay for detection of antibodies to the human immunodeficiency virus in whole blood samples

A silver-enhanced gold-labelled immunosorbent assay (SEGLISA) for the detection of antibodies to the immunodeficiency virus (HIV) in whole-blood samples is described. This new non-isotopic, non-enzymic immunoassay incorporates use of solid phase viral antigens which bind any HIV antibodies present in the test sample. The antigen/antibody complex is then detected by gold-labelled anti human immunoglobulin G (IgG) followed by silver amplification. We found that whole blood samples give false positives when using a horseradish peroxidase label, whereas the SEGLISA correctly identified 50 HIV antibody positive samples and 50 HIV antibody negative samples when using whole blood. The use of whole blood collected on filter paper is also described. The SEGLISA has good precision (CV = 7.5%) and sensitivity.