I developed an EC immunosensor by immobilizing antibodies on working electrode modified with carbon nano-tubes utilizing carbodiimide chemistry. when I investigated the immobilizing process by electrochemical impedance spectroscopy EIS , the Resistance of electron transfer (Rct) and the double layer capacitance Cd values increased after the immobilizing. How can I interpret the increasing in the Cd ?
I know that the Cd must be reduced due to the increasing of the thickness of the dielectric layer on the electrode surface .
Hi Abdulrahman Al-Shami ,
I thing your results must be positive and you are in right tract. Most of the immune sensors are based on potentiometric of impedimetric.
Since antibody is nonconducting and can block the catalytic site preventing the other redox reactions such as ferri-ferrocyanide reactions, accumulation of charged species takes place at the interface of the antibody modified electrode and the electrolyte.
More over, the immobilized antibody on the electron conducting transducers must be sensitive enough to detect small perturbations caused during the antibody-antigen interactions. Upon increasing the concentration of the analyte concentration the Rct values increases.
Rajendra Kumar Reddy Gajjala Thank you so much .
but how the immobilized antibody could increase the capacitance of the double layer ?
Hi, Abdulrahman Al-Shami ,
The exact mechanism was not understood completely. This was my prediction only. I assume like there may be chance of accumulation of hydration layer, lead to increasing in the capacitance. There may chance, antibody itself can induce the capacitance. It can be further enhanced during the antibody-antigen interaction.
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