Label-free electrochemical detection of human α-thrombin in blood serum using ferrocene-coated gold nanoparticles

This paper describes a novel approach to label-free electrochemical detection of human α-thrombin in human blood serum that utilizes ferrocene-coated gold nanoparticles (Fc-AuNPs). Human α-thrombin was specifically bound by the thiolated aptamers immobilized on the electrode. Positively charged Fc-AuNPs were electrostatically bound to the negatively charged aptamers. In principle, a high current peak should be observed in the absence of interactions between the aptamers and the human α-thrombin. This behavior indicates maximum adsorption of Fc-AuNPs by the negatively charged aptamers on the electrode surface. In contrast, when the thrombin-aptamer complex is formed, a low signal is expected because of the blocking capacities of the protein, which hinders the electrostatic binding of the Fc-AuNPs. The electrochemical signal, recorded by cyclic voltammetry and differential pulse voltammetry, indicates whether interactions between aptamers and proteins have occurred. There is a good correlation between the ferrocene oxidation peak intensity readings from our thrombin sensing system and the thrombin concentration, within the range of 1.2 μM-12 pM.