Electrochemical investigations of the interaction of C-reactive protein (CRP) with a CRP antibody chemically immobilized on a gold surface

A possibility of using a range of dc and ac electrochemical techniques to probe associative interactions of C-reactive protein (CRP) with CRP antibody (aCRP) immobilized on a gold electrode surface was investigated. It was demonstrated that the investigated electrochemical techniques can be used efficiently to probe these interactions over a wide CRP concentration range, from 1.15 × 10−5 to 1.15 mg L−1. The measured sensitivity of the techniques is in the following decreasing order: differential pulse voltammetry, charge-transfer resistance obtained from electrochemical impedance spectroscopy (EIS), cyclic voltammetry, chronoamperometry, and double-layer capacitance deduced from EIS measurements which gave the poorest sensitivity.Measurements of kinetic parameters demonstrated that the associative interactions of CRP with the immobilized aCRP reached quasi-equilibrium after 20–30 min. The kinetics of these interactions was modeled successfully using a two-step kinetic model. In this model, the first step represents reversible CRP–aCRP associative–dissociative interactions, while the second step represents the irreversible transformation of the bound CRP into a thermodynamically stable configuration. It was demonstrated that the thermodynamically stable configuration of CRP starts prevailing after 7 min of interaction of CRP with the immobilized aCRP.