Colloidal Gold: A Pluripotent Receptor Probe

Abstract

Colloidal gold is an electron-dense, lyophobic colloid that readily forms a stable electrostatic interaction with a variety of macromolecules. Monodispersed colloids ranging from 3-150 nm in diameter can be produced to provide the researcher with flexibility in selecting the optimally sized probe. Gold labeling of antibodies and lectins has been extensively used to study surface antigens and cell components. Recently, the use of gold labeling has been extended to study receptor-ligand binding, enzyme-substrate reactions, and transcellular pathways. Published applications include gold labeling of metabolites (low-density lipoproteins), enzymes (DNAase and RNAase, RNA polymerase, thrombin, collagenase, elastase), hormones (insulin, epidermal growth factor, glucagon), circulating plasma proteins (asialoglycoprotein, a2-macroglobulin, factor VIII-von Willebrand factor), and endotoxins (tetanus toxin, cholera toxin). This broad spectrum of applications emphasizes the versatility and usefulness of colloidal gold as a probe in areas of cell biology related to receptors, endocytosis, transport, and functions of proteins.

Ambiguities in Applying Traditional Limulus Amebocyte Lysate Tests to Quantify Endotoxin in Nanoparticle Formulations

“…The gold colloids may be binding the endotoxin and, thus, limiting its activity and/or accessibility to proteins in the LAL lysate. Gold has been shown to bind LPS and make it unavailable to LAL [15,16]. Similarly, it is not known why the PMLA nanoparticles cause enhancement of endotoxin detection.…”

Development of a novel gene delivery scaffold utilizing colloidal gold–polyethylenimine conjugates for DNA condensation

“…[11][12][13] In addition, colloidal gold has a history of use in biological and medical applications with no known inherent cytotoxicity. 10,14,15 Colloidal gold's high electron density allows its direct imaging via electron microscopy and its unique surface plasmon resonance properties provide a convenient handle on the aggregation state of the colloid. 10,14 Colloidal gold reacts selectively and covalently with thiol or disulfide-containing reagents, allowing a straightforward route to covalent ligand-gold conjugation for surface chemistry manipulation or targeting purposes.…”

“…12,13,16,17 Finally, it may also be possible to display targeting groups on the surface of the colloidal gold particles by simple direct physical adsorption. 15 Many investigators of nonviral gene scaffolds have used the charge ratio, or ratio of cations to anions in a formulation, to quantify the amount of polycationic carrier relative to the amount of DNA in their complexes. 1,18,19 In the case of polyethylenimine-based systems, the definition of charge ratio becomes ambiguous because the fraction of protonated amines in PEI/ DNA complexes at physiological pH is poorly understood.…”

Advanced protein glycosylation induces transendothelial human monocyte chemotaxis and secretion of platelet-derived growth factor: role in vascular disease of diabetes and aging.

“…Confluent endothelial monolayers were grown on a matrix composed of AGE-albumin conjugated to colloidal gold (25 nm) (18) and type IV collagen and exposed to monocytes as described above. At the end of incubation, monolayers were fixed for electron microscopy as described (19).…”