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Electrochemical Investigations of the Interaction of C-Reactive Protein (CRP) with a CRP Antibody Chemically Immobilized on a Gold Surface

Apossibility of using a range of dc and ac electrochemical techniques to probe associative interactions of Creactive protein (CRP) with CRP antibody (aCRP) immobilized on a gold electrode surfacewas 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 1.15mgL−1. The measured sensitivity of the techniques is in the following decreasing order: differential pulse voltammetry, chargetransfer 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. Itwas demonstrated that the thermodynamically stable configuration of CRP starts prevailing after 7 min of interaction of CRP with the immobilized aCRP.

C-reactive protein; Antibody–antigen interactions; Cyclic voltammetry; Differential pulse voltammetry; Chronoamperometry; Electrochemical impedance spectroscopy

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