Preparation and characterization of a colloidal gold-insulin complex with binding and biological activities identical to native insulin.
We studied the binding and biological activities of gold-insulin complexes to develop a complex with properties identical to native insulin. Stabilizing amounts of insulin absorbed to 5-, 10-, or 15-nm gold particles resulted in complexes with 40-327 insulin molecules per gold particle and 4-111 times the biological activity of unlabeled insulin, based on the molar concentration of gold complex. These data suggested that these complexes behaved as multivalent ligands. Gold-insulin complexes were prepared with 5% of the stabilizing insulin concentration and were stabilized with bovine serum albumin. This resulted in a complex with 5-7 insulin molecules per 10-nm gold particle, which stimulated glucose oxidation in rat adipocytes and competed with [125I]-insulin for binding to the insulin receptor identically to unlabeled insulin on an equimolar basis. The organization and distribution of insulin receptors occupied by this monovalent-behaving gold-insulin complex were virtually identical to previous observations using monomeric ferritin-insulin. Since multivalent ligands may affect receptor binding, re-distribution, and intracellular processing, the use of electron-dense probes that resemble the unlabeled ligand in biological and binding properties is appropriate when studying receptor dynamics of in vivo or in vitro biological systems. The gold-insulin complex developed in this study should serve this function.
Smith
R M
RM
Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia 19104.
Goldberg
R I
RI
Jarett
L
L
D000273:Adipose Tissue / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D001667:Binding, Competitive; D002462:Cell Membrane / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006046:Gold / Q000378:metabolism* / Q000494:pharmacology; D017979:Gold Colloid; D007328:Insulin / Q000378:metabolism* / Q000494:pharmacology; D008114:Liver Neoplasms, Experimental / Q000378:metabolism; D008854:Microscopy, Electron; D010084:Oxidation-Reduction; D010316:Particle Size; D051381:Rats; D011972:Receptor, Insulin / Q000378:metabolism*; D012710:Serum Albumin, Bovine; D014407:Tumor Cells, Cultured
D017979:Gold Colloid; D007328:Insulin; C055211:colloidal gold-insulin complex; D012710:Serum Albumin, Bovine; D006046:Gold; D011972:Receptor, Insulin; D005947:Glucose