The PolySorp surface should be used if the assay consists of less polar molecules with hydrophobic characteristics. In this system, streptavidin acts as a bridge between the capture antibody and an irrelevant, biotinylated protein which is adsorbed to a solid phase. Streptavidin bound directly to plastic surfaces is impaired in both its ability to bind to biotinylated monoclonal antibody and in its functional affinity when compared to streptavidin used in the PABC system. Therefore, it is not recommended to use streptavidin hydrophobically adsorbed to solid phase to immobilize biotinylated molecules. To optimize some use a buffer with a pH of 5 or 6.
Assay sensitivity depends strongly on an efficient removal of non-specific reacting molecules.
High background readings and coating instability can be eliminated by addition of a blocking step after the first coating. The excess surface is then occupied by indifferent molecules. Both of these surfaces are identical. The only difference between them is that for the certified plates, a representative sample from each manufacturing lot undergoes a Binding Capacity test. See Nunc Bulletin No. 4.