Lectins such as CF® Dye WGA Conjugates, CF® Dye Concanavalin A Conjugates, or CF® Dye PNA Conjugates can be used to label the cell surface or plasma membrane in FFPE or frozen sections. However lectins would label glycoproteins on all cell membranes, external (plasma membrane) as well as internal (organelle membranes). Lectin staining also is tissue- and cell-type dependent, based on the expression pattern of glycoproteins on the cell membranes. Therefore they generally do not selectively label all cell outlines or boundaries in a tissue section.
Other cell surface membrane stains such as the lipophilic CellBrite® or CellBrite® NIR dyes are not suitable for membrane staining in FFPE samples as membrane lipids are extracted during the dewaxing and rehydration process. Similarly, acetone or methanol fixation of cryosections will extract lipids, leading to poor staining.
CellBrite® Cytoplasmic Membrane Dyes may stain formaldehyde-fixed cryosections. However, because the cell membrane integrity is disrupted in frozen sections, CellBrite® dyes probably will not selectively stain the plasma membrane in tissue sections and will likely stain intracellular structures as well.
The reactive, fixable membrane stains, CellBrite® Fix and MemBrite® Fix are for live cell staining only. In fixed sections, they would indiscriminately react with target proteins throughout the cell, staining the entire cell.
Alternatively, immunostaining using cell surface-specific antibodies could be done.
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