Simple and sensitive electrochemical impedimetric approach towards analysis of biophysical interaction.

Study of biophysical interactions have been carried out using specific combination of proteins such as human IgG (as antigen) and anti-human IgG (as complementary antibody; raised in rabbit). Bovine serum albumin (BSA) was used to block any nonspecific interaction between antigen and antibody as BSA has been reported to bind to several sites non-specifically. Optimization of BSA concentration was done in order to make the antigen-antibody interaction relatively more pronounced and specific. We have used gold electrode in order to provide a relatively inert platform for adsorption/immobilization of protein molecules. The interaction between the antigen and antibody caused an increase in the charge transfer resistance (parallel resistance in Randles cell model) for an indicator molecule (hexacyanoferrate) and this was monitored by impedance spectroscopy. Detection limit for the antigen was found to be about 50 ng/mL. The approach presented is general and versatile and can be used for any antigen-antibody pair without any significant modification.