A new electrochemical immunoassay strategy for detection of transferrin based on electrostatic interaction of natural polymers

A new electrochemical immunoassay strategy was proposed based on electrostatic interaction of natural polymers. The chitosan-entrapped carbon paste electrode (CCPE) was used as the base electrode, alginates as carriers for the reactants and horseradish peroxidase (HRP) as enzyme label in the immunoassay. The immunoassay was firstly carried out using the homogeneous competitive immune format and a very high rate of immune reaction was reached since both reacting antibodies and antigens were in a solution phase. Subsequently quick heterogeneous separation of immune complexes attached to the alginates molecule from the solution phase was realized by making use of the strongly electrostatic attraction between the protonated amino groups of chitosans on the surface of CCPE and carboxylic groups of alginates. After washing the surface of CCPE, amperometric detection with hydroquinone and hydrogen peroxide as enzymatic substrates was carried out. A new surface of CCPE for repeated use in another assay can be obtained by polishing the original used one. The feasibility of the above approach was demonstrated using transferrin and transferrin-antibody as a model system. The dynamic concentration range for transferrin assay was 1.9 to 78.8 μg ml−1.