Application of a polyaniline based ammonium sensor for the amperometric immunoassay of a urease conjugated Tal 1 protein Original Research Article

An amperometric immunoassay was developed by coupling the enzyme-linked immunosorbent assay (ELISA) microtiter-plate system with a polyaniline-perfluorosulfonated ionomer composite (PA/NF) electrode incorporated flow injection analysis (FIA) system and used for the analysis of Tal 1 protein, found in leukemic T cell. Rabbit polyclonal antibody (pAb) against Tal 1 and urease–pAb were used, respectively as the captured protein and enzyme labeled conjugate for sandwich immunoassay of Tal 1. Characteristics of the PA/NF electrode such as reproducibility, stability and sensitivity were studied. The detection limits of the PA/NF electrode for NH4+ and urease were found to be 5 μM and 0.05 nM, respectively. Assay conditions such as the amount of pAb needed for coating the plate, the concentration of urease–pAb conjugate appropriate for the immunoreaction and the incubation time for urea to react with the bound urease–pAb in the microtiter-wells were also studied. A detection limit as lower as 0.5 ng/ml and a dynamic range of 1.0–100 ng/ml were found for the immunoassay of Tal 1 protein with the developed immunoassay system.