A polymer surface for antibody detection by using surface plasmon resonance via immobilized antigen

A polymer substrate based surface plasmon resonance (SPR) technique was developed for detection of specific monoclonal antibody 10B2 (MAb 10B2) against bacterium Acidovorax avenae subsp. citrulli (Aac). The monolayer of Aac antigen was physically immobilized on 95:5 polystryrene – copoly acrylic acid (95PSMA) for detection of antibody. The amount of antigen–antibody binding was found to depend on the surface density of immobilized Aac on the sensor surface and the antibody concentration. The detection limit was 5 μg/ml which was lower than the required concentration during the normal production of the antibody at 10–100 μg/ml. This suggests a possible use of surface for the antibody screening. Moreover, an application in antibody screening was explored by combination of surface plasmon resonance imaging (SPR imaging) and antibody detection assay on the 95PSMA surface. Two antigens of bovine serum albumin (BSA) and Aac were used as a model system for antibody screening. The result shows that both antibodies can be distinguished using the immobilized antigens on the 95PSMA surface based SPR imaging technique.     

Strategies to improve the surface plasmon resonance-based immmunodetection of bacterial cells

We have made a comparison of (a) different surface chemistries of SPR sensor chips (such as carboxymethylated dextran and carboxymethylated C1) and (b) of different assay formats (direct, sandwich and subtractive immunoassay) in order to improve the sensitivity of the determination of the model bacteria Acidovorax avenae subsp. citrulli (Aac). The use of the carboxymethylated sensor chip C1 resulted in a better sensitivity than that of carboxymethylated dextran CM5 in all the assay formats. The direct assay format, in turn, exhibits the best sensitivity. Thus, the combination of a carboxymethylated sensor chip C1 with the direct assay format resulted in the highest sensitivity for Aac, with a limit of detection of 1.6?×?10⁶ CFU mL^-1. This SPR immunosensor was applied to the detection of Aac in watermelon leaf extracts spiked with the bacteria, and the lower LOD is 2.2?×?10⁷ CFU mL^?1.