Chapter 13 Ultrasmall Gold Probes: Characteristics and Use in Immuno(cyto) chemical Studies

Abstract

Publisher Summary This chapter highlights ultrasmall gold probes. It describes its characteristics and uses in immuno (cyto) chemical studies. Markers are used either directly bound to the antigen-specific antibody (direct method) or linked to bridging molecules that bind specifically to the primary antibody (indirect method). Colloidal gold is preferred to radioactive or enzyme markers because of its particulate nature, which results in improved resolution. In addition, gold probes are nonhazardous reagents. Colloidal gold particles carry a net negative surface charge because of ions that are adsorbed on the surface of the particles. Positively charged proteins can therefore bind electrostatically. This phenomenon has been exploited to stain protein bands on blots and to develop a sensitive protein assay. Various considerations are taken into account when trying to improve the performance of colloidal gold probes, such as sensitivity of an immunogold reaction and sensitivity of detection. Gold probes based on ultrasmall particles are called “ultrasmall gold probes.” Contrary to the larger sized particles, uncoated ultrasmall colloidal gold particles are not stable and will aggregate in time. However, after adsorption to proteins the particles are stabilized and maintain their original size.