2-D PROTEIN CRYSTALS AS AN IMMOBILIZATION MATRIX FOR PRODUCING REACTION ZONES IN DIPSTICK-STYLE IMMUNOASSAYS

In the present study, the applicability of crystalline bacterial cell- surface layers (S-layers) as novel immobilization matrices and reactio n zones for dipstick-style immunoassays was investigated. For this pur pose, S-layer-carrying cell-wall fragments from Bacillus sphaericus CC M 2120 were deposited on a microporous support and the S-layer protein was cross-linked with glutaraldehyde. For developing appropriate test systems, either human Ige was directly linked to the carboxylic acid groups from the S-layer protein or it was immobilized using Protein A or after biotinylation, using streptavidin. A clear correlation was ob tained between the amount of anti-human Ige applied and the absorbance values in the immunoassays. S-layers with covalently bound recombinan t major birch pollen allergen were used for quantitative and semiquant itative determination of an antibody raised against it. Using S-layers as an immobilization matrix in comparison to amorphous polymers has a dvantages in that the closed monolayers of functional macromolecules o n their outermost surface allows for strong signals in immunoassays, a lmost completely eliminates background and prevents diffusion.