Substitution of carbonate by acetate buffer for IgG coating in sandwich ELISA

Monoclonal antibodies requiring coating buffer with low pH for efficient antigen capture in sandwich ELISA: the rarities or practically important phenomena?

This article reexamines some opinions concerning pH requirements for optimal immobilization of monoclonal antibodies (mAbs) by passive adsorption in antigen capture ELISA. It was discovered that substitution of "classical" sodium phosphate (pH 7.5) and carbonate (pH 9.5) coating solutions by acid (pH 2.8) buffers maximized antigen capture 4 out of 10 different tested anti-HBsAg mAbs, resulting in a 1.5-2.5 increase of binding curve coefficients. By measuring both mAbs amounts and functionality, the enhancement effect was attributed to the better preservation of solid phase antibodies activity.

Blocking of non-specific sorption in ELISA on formylated polystyrene beads

The effect of pH of the blocking solution on the non-specific sorption of peroxidase conjugates to the 0.63-cm formylated polystyrene beads was studied. Anti-G-HRP and BSA-HRP sorption was shown to dramatically depend on pH of blocking protein solutions and was minimum at pH=pI. Sorption of G-HRP weakly depended on pH of the blocking buffer. The blocking efficiency of proteins on unmodified beads, as well as of Tween-20 on formylated beads appeared to be pH independent. The optimized blocking step resulted in a multiple decrease in the non-specific sorption of conjugates on formylated beads.