Membrane & Cell Surface Stains

CellBrite® Cytoplasmic Membrane Stains are lipophilic dyes for simple, non-toxic, stable labeling of membranes in live or fixed cells. Cells can be fixed with formaldehyde before or after CellBrite® staining. But the staining has poor tolerance for permeabilization or methanol fixation, so CellBrite® staining is not easily combined with intracellular immunofluorescence (IF) staining. The dyes also do not stain bacteria or yeast. CellBrite® NIR Dyes are CellBrite® Dyes with near-infrared fluorescence compatible with small animal NIR imaging systems.

CellBrite® Fix and MemBrite® Fix stains were developed to overcome some of these shortcomings. They are novel covalent stains that can be fixed and permeabilized for IF staining. CellBrite® Fix Membrane Stains are fluorogenic reactive membrane dyes that rapidly accumulate at the plasma membrane. When they incorporate into lipids, they become fluorescent, and at the same time react covalently with membrane proteins for stable labeling. Staining takes only 15 minutes in a single step with no wash. CellBrite® Fix stains mammalian cells, yeast, and bacteria. CellBrite® Fix reacts with plates coated with poly-L-lysine, collagen, gelatin, or other proteins, resulting in high background. The dyes tend to have high background on uncoated cell culture surfaces as well. Imaging cells by confocal microscopy can reduce interference from out-of-plane background fluorescence.

MemBrite® Fix Cell Surface Stains do not bind lipids, but label cell surface proteins. MemBrite® Fix requires a two-step staining protocol with washing, but offers a more extensive choice of dye colors than CellBrite® Fix. MemBrite® Fix also can be used to stain yeast and Gram-positive bacteria. But unlike original CellBrite® Dyes and lectins, CellBrite® Fix and MemBrite® Fix cannot be used on cells that are already fixed. While we do not expect MemBrite® Fix stains to react with poly-L-lysine coated surfaces, we have seen high background with these types of plates and with uncoated cell culture surfaces. To circumvent this issue, we recommend imaging cells by confocal microscopy to reduce out-of-plane background fluorescence. The stains will react with surfaces treated with collagen, gelatin, fibronectin, or other extracellular matrix protein coatings.

GlycoLiner™ Cell Surface Glycoprotein Labeling Kits are designed for covalent labeling of glycoproteins on the surface of live cells. Like CellBrite^® Fix and MemBrite^® Fix, staining can withstand fixation and permeabilization. GlycoLiner™ also offers less cytoplasmic background in dead cells than CellBrite^® Fix and MemBrite^® Fix, allowing easier imaging of cell surfaces. GlycoLiner™ can also be used to stain yeast and Gram-positive bacteria. GlycoLiner™ is not expected to react with poly-L-lysine-coated surfaces, however, glycosylated matrix components like collagen or proteoglycans in complex matrices like Matrigel® may be labeled.

CytoLiner™ Fixed Cell Membrane Stains are novel lipophilic fluorescent dyes developed for selective plasma membrane staining in fixed cells and are suitable for downstream immunofluorescence staining protocols. Please note, staining with CytoLiner™ Dyes is not compatible with cells fixed using solvents like methanol or acetone, or with paraffin-embedded samples, because these treatments will remove the lipids from cells, which are required for CytoLiner™ staining. For co-staining with antibodies, we recommend staining with CytoLiner™ Dye first, then blocking with 2% fish gelatin in PBS, followed by antibody incubation in the same buffer. Blocking with BSA or serum is not recommended. CytoLiner™ staining is compatible with poly-L-lysine coated culture surfaces and Transwell® permeable supports. For best results, confocal microscopy is recommended for imaging fluorescent staining of Transwell® supports to avoid background from the filter material.

To select a dye that’s right for your application, see our Membrane and Cell Surface Stains Comparison, or download our Membrane & Surface Stains Brochure.

CellBrite® Cytoplasmic Membrane Dyes are too prone to aggregation to efficiently stain EVs. Some of the CellBrite® Fix, MemBrite® Fix, and CellBrite® Steady dye options have been reported for this application, however we do not recommend them. For optimal staining of exosome membranes we recommend our ExoBrite™ True EV Membrane Stains, which are novel lipophilic membrane dyes specifically designed and optimized for efficient staining of EV membranes with minimal dye aggregation. See our Extracellular Vesicle Research page for more information about our complete line of EV stains and antibodies.

Biotium’s CellBrite® Cytoplasmic Membrane Dyes are dye delivery solutions that can be added directly to normal culture media to uniformly label suspended or adherent cells in culture. The PKH dyes are structurally related dyes for cell membrane labeling. But unlike CellBrite®, labeling with PKH dyes requires multiple steps and subjects cells to an iso-osmotic mannitol loading medium that can negatively affect cell membrane integrity and viability.

CellBrite® Fix dyes also feature rapid and simple labeling in isotonic buffer. Cells can be fixed and permeabilized after labeling with CellBrite® Fix, unlike original CellBrite® dyes or PKH dyes, which don’t tolerate detergent.