Cell Surface Markers and Labeling Techniques for Scanning Electron Microscopy

Abstract

Cell surface labeling has provided valuable information on the organization and dynamics of specific antigens and receptors in cell membranes. Such studies have generally utilized fluorescent dyes, radioisotopes, enzymes or biological macromolecules (ferritin, hemocyanin, viruses) bound to specific ligands (antibodies, lectins, hormones and toxins) as visual probes for light and transmission electron microscopy (TEM). More recently, visual markers and labeling methods have been developed for scanning electron microscopy (SEM). These techniques have been used to map the topographical distribution of specific molecules on complex cell surfaces (1).Visualization of cell labeling by SEM relies on the use of macromolecular markers which are resolvable under the SEM. Such markers also must i) be uniform in size and shape to facilitate their identification on cell surfaces, ii) show little, if any, nonspecific binding to cell surfaces, iii) interact with surface specific ligands via covalent bonding or high affinity binding and iv) be stable against degradation or aggregation during labeling and preparation of samples for SEM.