Plate Treatments and coating

Plate Treatments and Coatings 

l  Plates for cell-based assays

¡  Tissue-culture treated plates

¡  Poly-lysine-coated plates

¡  Collagen-coated plates

¡  Sterility

 

l  Plates for biochemical assays

¡  Polyethyleneimine (PEI)-coated plates

 

l  Protein-coated plates

¡  Streptavidin-coated plates

¡  Antibody-coated plates

Plates for Cell-based Assays

Tissue-culture treated plates

Polystyrene plastic must be subjected to a surface treatment to render the plastic suitable for cell attachment. Untreated polystyrene surfaces are not suitable for cell attachment due to the surface chemistry of the polystyrene. The tissue culture treatment process involves exposing a polystyrene microplate to a plasma gas in order to modify the hydrophobic plastic surface to make it more hydrophilic. The resulting surface carries a net negative charge due to the presence of oxygen-containing functional groups such as hydroxyl and carboxyl. In general, this will lead to increased cell attachment.

 

Poly-lysine-coated plates

Poly-lysine is a synthetic positively-charged polymer, existing as two enantiomers: Poly-D-lysine (PDL) and Poly-L-lysine (PLL). Adherence of certain cell types to poly-lysine-coated surfaces is based on the electrostatic interaction of the poly-D-lysine polycation with the negative charges of the cell membrane. Use of poly-lysine coatings on plate surfaces can help mediate the negative charges of the cell membrane and the negative charge of the surface. Both PDL and PLL are commonly used however PDL is not degraded by cellular proteases and is therefore often the preferred choice. As Poly-lysine is a synthetic protein, it does not influence the signaling pathways of the cells and is completely free of any animal contaminants. Almost all cell types will adhere to Poly-lysine coated plate bottoms.

 

Collagen-coated plates

Extracellular matrix proteins such as collagen provide an attachment framework for the adhesion and growth of certain cell types in vivo, and can also be used for cell attachment to plate surfaces in vitro. Cellular fibronectin membrane proteins mediate the attachment of cells to collagen substrates. Collagen is the most abundant protein in mammals that is found throughout the body and is a major component of the extracellular matrix (ECM). The most frequently used types of collagen for coating are collagen I and IV. Collagen type I is suitable for endothelial and epithelial cells, muscle cells and hepatocytes. Collagen type IV is the major constituent of basement membranes and offers more physiologically relevant conditions to cells as well as improving the adherence of specific cell types i.e. PC-12 (rat adrenal pheochromocytoma cell line). Our catalog plates are coated with rat tail collagen Type I.

 

Sterility

All tissue-culture treated plates are sterilized using gamma irradiation to prevent contamination.

Plates for biochemical assays

Polyethyleneimine (PEI)-coated plates

Polyethyleneimine (PEI) is a cationic polymer that can neutralize the negative charge of glass fiber filters (GF/C, GF/B). Treating GF/C and GF/B filter plates with polyethylenimine (PEI) is often used to minimize non-specific binding, particularly in ligand-binding assays. For some applications involving negatively-charged ligands (such as GTP binding assays), PEI coating could cause problems by creating a positively-charged surface that actually promotes non-specific binding to the filter, due to the negative charge on the ligand.

 

PEI coating is also sometimes used to coat the surface of glass plates, to neutralize the negative charge of the glass. This can help facilitate cell attachment in certain situations.

Protein-coated plates

Streptavidin-coated plates

Streptavidin-coated plates are often used to create generic plates for solid-phase (coated plate) assays, such as ELISA assays, DELFIA® immunoassays, and FlashPlate® assays. Streptavidin will bind biotinylated antibodies, biotinylated proteins, and other biotinylated moieties, anchoring the biotinylated reagent to the well of the plate.

  

Antibody-coated plates

Antibody-coated plates are also frequently used to create plates for solid-phase (coated plate) assays. Some of our DELFIA plates for DELFIA fluorescence assays as well as some of our FlashPlate microplates are offered pre-coated with anti-species antibodies, to be used to anchor a relevant antibody to the plate.

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