Antigen-antibody affinity transduction

Scheme 13 Electronic and optical transduction of the formation of antigen-antibody affinity complexes on transducers (A) ampero-metric transduction at an electrode (R+/Ris a redox label in the electrolyte solution), (B)...

The use of the electrode surface as solid phase in immunoassay can present some problems a shielding of the surface by antibody or antigen molecules can cause hindrance in the electron transfer, resulting in a reduced signal and so a loss of sensitivity. There are different ways that can be used to improve the sensitivity of the system an interesting approach could involve the screen-printed electrodes are used only for the transduction step, whereas the affinity reaction could be performed using another physical support [24]. 

In contrast the use of the antibodies for the detection of antigens has not an amplification stage involved and then the affinity reaction should be amplified in order to have a clear transduction. We have two possibilities, one is the use of a bioconjugate involving a bound enzyme, like in the classical ELISA test the second is the inherent amplification given by the mass of the biological element involved, a piezoelectric device (sensitive to mass) can detect minute amount of large proteins (like antibodies) if they are attracted on the surface of the sensor. 

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